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Biomedical subjects

R K Nakamura

Publications and source records attributed to R K Nakamura.

17 recordsLinked to original sources
PubMed1997

Positive correlations between cerebral protein synthesis rates and deep sleep in Macaca mulatta.

Local rates of cerebral protein synthesis (ICPSleu) were determined with the autoradiographic L-[1-14C]leucine method in seven awake and seven asleep, adult rhesus monkeys conditioned to sleep in a restraining chair in a darkened, ventilated chamber while EEG, EOG, and EMG were monitored. Prior to the period of measurement all animals slept for 1-4 h. Controls were awakened after at least one period of rapid-eye-movement (REM) sleep. Experimental animals were allowed to remain asleep, and they exhibited non-REM sleep for 71-99% of the experimental period. Statistically significant differences in ICPSleu between control and experimental animals were found in four of the 57 regions of brain examined, but these effects may have occurred by chance. In the sleeping animals, however, correlations between ICPSleu and percent time in deep sleep were positive in all regions and were statistically significant (P < or = 0.05) in 35 of the regions. When time in deep sleep was weighted for the integrated specific activity of leucine in grey matter, positive correlations were statistically significant (P < or = 0.05) in 18 regions in the experimental animals. These results suggest that rates of protein synthesis are increased in many regions of the brain during deep sleep compared with light sleep.

Animals↗
PubMed1987

Attention-related unit activity in the frontal association cortex during a go/no-go visual discrimination task.

Unit activity related to a go/no-go visual discrimination task was studied in four rhesus monkeys. We recorded 272 task-related cells from frontal cortex in a region extending from the midprincipal sulcus to the central sulcus, and medially to the cingulate sulcus. Units located in anterior regions (dorsolateral prefrontal and anterior cingulate cortex) were typically related to both go and no-go trials (designated type II units) and showed similar ("symmetrical") activity in both kinds of trials; some of them also showed prestimulus ("anticipatory") activity. Such units were present but less common in posterior regions (postarcuate and precentral and posterior cingulate cortex). Units in these posterior regions were active predominantly in go trials (designated type I units). Also found posteriorly were "asymmetrical" type II cells whose activity was greater in go trials and occurred later in the trial, around the behavioral response. The anterior symmetrical and anticipatory type II units in the frontal association cortex were similar to such units described earlier in the brain stem reticular formation and may have similar functions in supporting focused and preparatory attention. On the other hand, asymmetrical type II units in the posterior frontal regions may have a role in the initiation of visually guided motor behavior.

Action Potentials↗
PubMed1987

Effects of gamma-hydroxybutyrate on the performance of monkeys in a Go/No-go visual discrimination task.

It has been suggested that monkeys, administered gamma-hydroxybutyrate (GHB), manifest a state resembling petit mal status. This implies that an animal would produce erroneous responses immediately prior to, and discontinue behaviors requiring any cognitive effort concurrently with, an episode of GHB-induced generalized 3 cps wave-spike bursts in the EEG. This prediction was not confirmed in the present study. Rhesus macaques (Macaca mulatta) were trained to perform in a visual discrimination Go/No-go test. Thereafter bipolar transcortical electrodes were implanted in the hemisphere contralateral to the preferred hand. All monkeys discontinued to lever-press for water reward when administered GHB (125 or 250 mg/kg, esophageal intubation) and exhibited signs of reduced postural control and somnolence punctuated by episodes of hypermotility about 40-50 min after GHB. However, the monkey's difficulties in completing the program were not associated with the development of generalized hypersynchronous EEG activity. While occasional wave-spike bursts did occur, they were poorly regulated, often 'focal' (i.e. developed only in isolated areas), and had a frequency of 1.5-2 cps. In this state, animals could be easily roused by sensory stimuli. All of them reacted with a characteristic aversive-aggressive display when confronted by a direct gaze. These effects are interpreted to be more consistent with characterization of GHB activity as that of a potent hypnotic rather than a convulsant agent.

Animals↗
PubMed1986

Chronic 'blindness' following lesions of nonvisual cortex in the monkey.

Chronic 'blindness' was produced in monkeys by a lesion that combined right optic tract section, forebrain commissurotomy, and a large cortical ablation in the left hemisphere that spared most of the modality specific visual cortex. The finding suggests that, contrary to implications from earlier studies, central visual processes can influence behavior only with the participation of nonvisual cortex.

Animals↗
PubMed1986

Visual responses from cells in striate cortex of monkeys rendered chronically 'blind' by lesions of nonvisual cortex.

Chronic 'blindness' can be produced in monkeys by a large cortical removal that spares modality specific visual cortex (striate, prestriate, and inferior temporal cortex). To understand the reasons for the blindness we compared single unit activity recorded from striate cortex of these monkeys with the activity of units recorded from seeing animals. The results indicate that visual processing in the striate cortex of the blind monkeys, with the exception of changes attributable to a partial disruption of the geniculostriate pathway, is similar to that of the normal monkeys. The chronic blindness is therefore probably due not to dysfunction within striate cortex but rather to a disconnection from critical processing stages within the ablated territory. Feedback from this territory is apparently not necessary for information processing to occur in striate cortex.

Animals↗
PubMed1984

Adrenal medulla grafts survive and exhibit catecholamine-specific fluorescence in the primate brain.

Parkinson's disease most consistently involves pathologic changes in the substantia nigra, which is the major source of dopamine to the striatum. It has been shown that either fetal substantia nigra or adrenal medulla tissue implanted into the rat brain survives, produces dopamine, and improves behavioral abnormalities induced by deprivation of the caudate nucleus of its dopaminergic innervation. Thus, catecholamine-containing grafts could be potential replacements for destroyed or damaged dopaminergic neurons in patients with Parkinson's disease. To explore the potential of this therapeutic approach, fetal substantia nigra or host adrenal medulla were grafted to the denervated caudate nucleus of the rhesus monkey. Under the specific conditions of our experiment, fetal substantia nigra did not survive in either of two animals tested. On the other hand, some tissue from adrenal medulla grafts survived in all four animals tested. These grafted cells contained catecholamines, as indicated by the presence of specific glyoxylic acid-induced catecholamine fluorescence. In two of the four animals, however, the grafts contained fewer than 10 surviving cells, and in the other two animals, about 190 and 300 cells were found, respectively. Despite the small numbers of cells, this is the first demonstration that peripheral tissue autografts can survive implantation into the nonhuman primate central nervous system.

Adrenal Medulla↗
PubMed1983

Hypnogenic center theory of sleep: no support from metabolic mapping in monkeys.

By comparing rates of glucose utilization in brains of monkeys in non-REM sleep and two types of awake controls, we attempted to reveal cerebral hypnogenic centers that drive organisms to sleep through increases in their neural activity. Instead we found that metabolic activity is reduced in all the putative hypnogenic centers during sleep as compared to wakefulness. The results thus offer no support for the notion of an active center that either maintains or triggers sleep.

Animals↗
PubMed1982

A flexible restraint chair for the cynomolgus monkey (Macaca fascicularis).

We have found that commercial restraint chairs suitable for the rhesus monkey (Macaca mulatta) cause severe physical distress to many cynomolgus monkeys (Macaca fascicularis). A new restraint chair has therefore been designed specifically for the cynomolgus. The key features of the chair are an angled neck piece, a large opening to provide free movement for the tail, a soft waist restraint, and a level surface for both the heels and ischial pads. This new chair is not only suitable for the cynomolgus monkey but may also be more comfortable for the rhesus monkey than standard commercial chairs.

Animals↗