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Biomedical subjects

M Miyaoka

Publications and source records attributed to M Miyaoka.

At least 37 records · Page 2Linked to original sources
PubMed1990

The lumped constant of the deoxyglucose method in hypoglycemia: effects of moderate hypoglycemia on local cerebral glucose utilization in the rat.

The applicability of the [14C]deoxyglucose method for measuring local cerebral glucose utilization (lCMRglc) has been extended for use in hypoglycemia by determination of the values of the lumped constant to be used in rats with plasma glucose concentrations ranging from approximately 2 to 6 mM. Lumped constant values were higher in hypoglycemia and declined from a value of 1.2 at the lowest arterial plasma glucose level (1.9 mM) to about 0.48 in normoglycemia. The distribution of glucose, and therefore also of the lumped constant, was found to remain relatively uniform throughout the brain at the lowest plasma glucose levels studied. lCMRglc in moderate, insulin-induced hypoglycemia (mean arterial plasma glucose concentration +/- SD of 2.4 +/- 0.3 mM) was determined with the appropriate lumped constant corresponding to the animal's plasma glucose concentration and compared with the results obtained in six normoglycemic rats. The weighted average rate of glucose utilization for the brain as a whole was significantly depressed by 14% in the hypoglycemic animals, i.e., 61 mumols/100 g/min in hypoglycemia compared to 71 mumols/100 g/min in the normoglycemic controls (p less than 0.05). lCMRglc was lower in 47 of 49 structures examined but statistically significantly below the rate in normoglycemic rats in only six structures (p less than 0.05) by multiple comparison statistics. Regions within the brainstem were most prominently affected. The greatest reductions, statistically significant or not, occurred in structures in which glucose utilization is normally high, suggesting that glucose delivery and transport to the tissue became rate-limiting first in those structures with the greatest metabolic demands for glucose.

Algorithms↗
PubMed1990

Chronological alterations of regional cerebral blood flow, glucose utilization, and edema formation after focal ischemia in hypertensive and normotensive rats. Significance of hypertension.

The chronological changes of ischemic brain edema, rCBF, and LCGU were examined in SHR and WKY 6, 24, and 48 hr after MCAO. The analysis focused on the ischemic periphery in the cortex at the level of caudate nucleus. The ischemic areas in the cortex as identified on stained sections were more extensive in rats with hypertension than in those with normotension. The swelling of the ischemic hemisphere progressed until 48 hr after MCAO in hypertension; however, the peak of brain swelling was found at 24 hr in normotension and then resolved 48 hr after MCAO. The water content was also increased in hypertension at 48 hr after MCAO. Determination of rCBF and LCGU was made by a double-label autoradiographic method using [14C]deoxyglucose and [14C]iodoantipyrine. In the early period (6 hr) after MCAO, the reduction of rCBF was greater than the reduction of LCGU in both hypertension and normotension, indicating misery perfusion. After 24 and 48 hr of MCAO, the rCBF and LCGU recovered in normotension; however, the progressive reductions in rCBF and LCGU were observed in hypotension. These results suggest that an increased hydrostatic pressure gradient in the ischemic periphery may play an important role in the development of edema and impairment in both rCBF and LCGU.

Animals↗
PubMed1988

Measurement of local cerebral glucose utilization before and after V-P shunt in congenital hydrocephalus in rats.

Local cerebral glucose utilization (LCGU) was measured by the [14C]deoxyglucose autoradiographic method in rats with congenital hydrocephalus before and after a V-P shunt. LCGU was decreased throughout the brain in hydrocephalus. The most severely affected regions were found in the cortex, with which a marked degree of subcortical cerebrospinal fluid (CSF) edema was associated; regions in the brain-stem structures were less affected. These metabolic disturbances were improved in many regions after a V-P shunt. However, no improvement was found in the cortex; therefore, damage was considered irreversible. CSF edema was also found in the periaqueductal gray matter in which impaired LCGU was observed; however, this metabolic disturbance was normalized after a V-P shunt. This study suggests that regional differences in the brain seen in hydrocephalus and CSF edema may have varying ill effects on cerebral metabolism. Without prompt treatment, metabolic damage progresses and becomes irreversible. It is suggested that metabolic impairment in the brain stem which is reversible is due mainly to increased intracranial pressure (ICP).

Animals↗
PubMed1988

Intraorbital meningiomas. Surgical management and role of radiation therapy.

The authors discuss their experience with 11 cases of intraorbital meningioma, revealing how computed tomography scanning has aided in early diagnosis of primary optic nerve meningiomas. Despite the difficulty of removing apical, primary optic nerve meningioma without sacrificing the central retinal artery, the authors prefer a surgical approach backed up by radiation therapy. It appears that general improvement, although generally elusive, is worth the risk incurred in trying to overcome the deficits stemming from these tumors.

Adolescent↗
PubMed1988

[Diurnal variation in glucose utilization in the pineal body of the monkey].

We employed the quantitative 2-[14C]-deoxyglucose method (Sokoloff's method) to measure glucose utilization in the pineal gland of pubescent monkeys. Glucose utilization in the pineal was 80-110% higher in the nocturnal, awake animals compared to the rate of both groups studied in the nocturnal, awake animals with both eyes open and with light deprivation for three hours. Short term visual deprivation during the day was without effect on pineal glucose utilization. The diurnal variations in melatonin levels in blood and CSF, higher at night than during the day, are the result of corresponding changes in the rate of production and elaboration of melatonin in the pineal gland. The release of norepinephrine from the postganglionic fiber of the superior cervical ganglia controls the production of melatonin in the pineal by regulating the activity of serotonin-N-acetyltransferase. It was reported that electrical stimulation of SCG via sympathetic trunk increased the levels of serotonin-N-acetyltransferase in the pineal and that it also increased glucose utilization in the pineal. It is believed that metabolic increase in the pineal reflects increased activity in sympathetic terminals distributed throughout the gland which stimulate its increase in hormone production. The present results indicate that there is an elevation of pineal metabolic rate at a time when blood and CSF levels of melatonin are known to be elevated Our finding that short-term light deprivation during the day did not affect the pineal metabolic rate is consistent with the result by Reppert et al (1981) in which they found that exposure to darkness during the day does not result in an increase in CSF melatonin.

Animals↗
PubMed1984

Metabolic and behavioral consequences of lidocaine-kindled seizures.

Daily administration of lidocaine results in progressive increases in frequency and duration of convulsions in response to a dose of drug which was previously subconvulsive--a pharmacological kindling phenomenon. The effects of such lidocaine-kindling on local cerebral glucose utilization were determined by the 2-[14C]deoxyglucose method. Lidocaine-treated animals, in the absence of convulsions, exhibited decreased glucose utilization in most brain structures compared to saline-treated animals and showed no increase in aggressive behavior. In animals displaying lidocaine-kindled convulsions there were marked increases in glucose utilization in either the hippocampus and amygdala or in perirhinal cortical areas during the seizure administration; these animals also displayed long-lasting increases in irritable behavior. Seizure duration was positively correlated with the rate of glucose utilization in the hippocampus, amygdala and septum, but inversely correlated in several non-limbic areas. These data suggest that lidocaine-kindled seizures are highly localized to limbic and perirhinal structures and are associated with important behavioral consequences.

Aggression↗
PubMed1984

Cervical radiculomyelopathy due to calcification of the ligamenta flava.

Three cases of cervical radiculomyelopathy caused by calcification of the ligamenta flava of the cervical spine are reported. A review of the literature yielded 13 cases of calcification of the cervical ligamenta flava with findings similar to those in our cases. Specifically, we observed that 1) all patients were more than 50 years of age; 2) most were female; and 3) the calcifications appeared consistently as oval nodules, located symmetrically and paramedially in and around the region of the fifth cervical vertebra. Such characteristic similarities in both clinical and radiologic features are important in considering the etiology of calcification of the cervical ligamenta flawa.

Aged↗
PubMed1984

[Alterations in local cerebral glucose utilization during various anesthesia--the effect of urethane and a review].

Anesthetic is thought to depress the energy metabolism or oxygen consumption of the brain as a whole. It has been clear, however, that anesthetic agent may either decrease or increase local metabolic rate of the brain since [14C] 2-deoxyglucose method made one possible to measure local cerebral glucose utilization. In this paper, the authors report the effect of urethane anesthesia on the local cerebral glucose utilization. We measured local cerebral glucose utilization by means of [14C] 2-deoxyglucose method in 87 brain structures of albino rats (about 300 g) under urethane anesthesia, 1 g/kg (n = 5), and conscious state (n = 6). When the whole brain metabolism was computed as a weighted average with the acid of the computerized image-processing system, there was 33% reduction in glucose utilization of the brain as a whole in the rats under urethane anesthesia. Urethane decreased the local rate of glucose metabolism, but the metabolic effect was not homogeneous throughout the brain. The neural structures in which no metabolic depression was observed were entorhinal cortex, many nuclei in hypothalamus, medial habenula-interpeduncular nucleus, nucleus tractus solitarius, and some white matters. The selective metabolic sparing in the habenula-interpeduncular system was also reported to be observed during chloral hydrate and enflurane anesthesia. However, the mechanism involved in the phenomenon remains unclear. In the discussion, we discussed the differential effects of various anesthetics of the local cerebral glucose utilization. We reviewed the literatures on the effects of various anesthetics; barbiturate, chloralose, chloral hydrate, enflurane, ketamine, nitrous oxide and halothane on the local rate of metabolism of the brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1983

[Radiculomyelopathy due to calcification of the cervical ligamenta flava--report of 2 cases and a review of literature].

Calcification of ligamenta flava in the cervical spine is rarely seen. Only few cases in the literature have been available. Recently we have had experience with two cases on that lesion who had progressive radiculomyelopathy. The purpose of this report is not only case presentation but also an analysis of 11 cases from the literature in clinical, radiological and histological aspects. Case 1 was a 60-year-old woman who had numbness in both hands, mild weakness of the right foot on walking and clumsiness of the right hand. Ten years before she had suffered tbc. meningitis, but no history of neck injury. Neurological examination revealed spastic paresis in right extremities, muscle atrophy in both forearms, hypesthesia and hypalgesia in both hands and feet. Vibration sense was disturbed below the knee joint and both feet. Sphincter function was normal. Radiological examination of cervical spine revealed oval calcified nodules in the posterior spinal canal at the level of C34, C45, C56 and C67. These were all situated in the paramedian portion and symmetrically situated at C56. Air myelogram demonstrated that the spinal cord was displaced forward and choked by the posterior situated calcification. Cervical laminectomy was carried out from C2 through Th1 and calcified nodules in the hypertrophied ligamenta flava were successfully removed. Case 2 was also 66-year-old woman who had been suffering from cerebral thrombosis with left hemiparesis. In addition with left hemiparesis she started to complain with paresthesia in right hand, deteriorated numbness in left extremities and gait disturbance developed a year later.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1982

Mapping the primate visual system with [2-14C]deoxyglucose.

The [2-14C]deoxyglucose method was used to identify the cerebral areas related to vision in the rhesus monkey (Macaca mulatta). This was achieved by comparing glucose utilization in a visually stimulated with that in a visually deafferented hemisphere. The cortical areas related to vision included the entire expanse of striate, prestriate, and inferior temporal cortex as far forward as the temporal pole, the posterior part of the inferior parietal lobule, and the prearcuate and inferior prefrontal cortex. Subcortically, in addition to the dorsal lateral geniculate nucleus and superficial layers of the superior colliculus, and structures related to vision included large parts of the pulvinar, caudate, putamen, claustrum, and amygdala. These results, which are consonant with a model of visual function that postulates an occipito-temporo-prefrontal pathway for object vision and an occipito-parieto-prefrontal pathway for spatial vision, reveal the full extent of those pathways and identify their points of contact with limbic, striatal, and diencephalic structures.

Animals↗
PubMed1982

Local cerebral glucose utilization in the newborn macaque monkey.

The [14C]deoxyglucose method for quantitative determination of local cerebral glucose utilization was employed in newborn macaque monkeys. Values ranged from a high of 180 mumol/100 gm/min in the inferior colliculus to a low of 14 mumol/100 gm/min in the centrum ovale, a wider range than had been found in this laboratory for pubescent monkeys. Relatively low values in white matter overlapped with the generally higher values in gray matter. Rates for structures in the lower neuraxis were equal to or exceeded those reported for the mature animal, while those above the midbrain were generally lower. The auditory system was unique in having rates equal to, or exceeding, its mature levels in all parts of the pathway including the cortex. In the visual system, subcortical structures were at their mature levels while rates in the cortical areas were variably low; nevertheless, the striate cortex had differential rates marking the various laminae. It was possible to demonstrate the metabolic counterpart of the ocular dominance columns in two newborn animals that had had one eye occluded during the experiment. Rates for white matter were above their mature levels, with the differences being greatest in the brainstem and cerebellum. A high correlation between glucose utilization and local blood flow measured with [14C]antipyrine (r = 0.92) was found.

Animals↗
PubMed1981

Changes in protein synthesis underlying functional plasticity in immature monkey visual system.

Local rates of cerebral protein synthesis were determined in newborn rhesus monkeys subjected to either acute or chronic monocular visual deprivation. Chronic monocular deprivation resulted in decreased rates of protein synthesis in the laminae of the lateral geniculate nuclei innervated by the deprived eye whereas rates of protein synthesis were normal in geniculate laminae innervated by the functioning eye. Acute monocular deprivation produced no differential changes in rates of protein synthesis in any of the geniculate laminae.

Animals↗
PubMed1981

Comparative rates of local cerebral glucose utilization in the visual system of conscious albino and pigmented rats.

We measured local cerebral glucose utilization by means of the [14C]deoxyglucose technique in normal, conscious albino Sprague-Dawley and pigmented Norway rats in the ambient light of the laboratory. There were no differences between the two strains in any structures except those of the visual system. The rates of glucose utilization in all components of the visual system were lower in the albino than in the pigmented rats. The affected structures and percent differences were as follows: visual cortex (17%); stratum griseum superficialis (28%), stratum opticum (17%), and stratum lemnisci (10%) of the superior colliculus; dorsal nucleus (34%) and ventral nucleus (33%) of the lateral geniculate body; and posterolateral thalamus (10%). All differences were statistically significant (p < 0.05) except those in the striatum lemnisci and posterolateral thalamus. These results indicate that the known aberrant neurophysiologic function of the visual system of the albino rats is paralleled by alterations in metabolic activity of its component structures.

Albinism↗