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Biomedical subjects

R Nakamura

Publications and source records attributed to R Nakamura.

At least 469 records · Page 26Linked to original sources
PubMed1981

The interference effect of simultaneous vocalization on manual reaction time.

Simple reaction times (RTs) of the left or right hand with or without simultaneous vocalization were examined in 14 right-handed subjects. RTs of the simultaneous tasks were longer than those of the single tasks and slowing of RT was larger on the manual than vocal response, particularly on the right side. The results are interpreted as reflecting a different mode of processing in the left and right hemispheres.

Adult↗
PubMed1981

The interference effect of simultaneous vocalization on reaction time of hand and foot.

Reaction times (RTs) of 14 normal subjects were examined in two tasks; the extension of the right middle finger, or of the right toe or the vocalization responding to the sound stimulation (single tasks), and the simultaneous responses of the two mentioned above (simultaneous tasks). RT of each part was longer on the simultaneous response than on the separate one. Slowing of the vocal response combined with the foot was larger than that with the hand and slowing of the foot with the vocalization was larger than that with the hand. The results were interpreted as indicating that the slowing of RT in the simultaneous responses should occur at the levels of the premotor associations, including the basal ganglia and cerebellum, but not at the level of the motor cortex.

Adult↗
PubMed1981

Dependence of reaction time on visual fields in patients with unilateral hemispheric lesions.

Reaction times (RTs) to light stimuli which appeared at central and lateral positions were measured in 13 normal subjects and 34 patients with unilateral lesions in the left or the right hemisphere. The normal subjects showed slowing of RTs to both lateral stimuli compared to the central stimulus, the extent of which was equal between the left and right hands. The patients with left hemispheric lesions had slower RTs to the stimulus contralaterally to the lesion than ipsilaterally and centrally. The patients with right hemispheric lesions had slower RTs both to the contralateral and central stimuli than to the ipsilateral. The results are discussed in relation to functional differentiation of the left and right hemispheres for visual processing.

Brain Diseases↗
PubMed1981

Disturbances of rhythm formation in patients with hemispheric lesion.

A total of 191 patients with hemispheric lesion mainly due to CVD were examined by the finger-tapping test, and their disturbances of rhythm formation, 'hastening phenomenon' (HP), were compared with those of Parkinson's disease. HP was observed in 56% of the right and 49% of the left hemiplegic patients. HP in the intact hand of the patient was highly correlated with that of the affected hand. CT scans were examined in 86 of 191 patients, and HP was specifically correlated with unilateral striatal lesions. Thus, the disturbances of rhythm formation in hemiplegia, together with those in Parkinson's disease, Huntington's chorea, SND and OPCA, were attributed either to organic or functional deficits in the striatum.

Cerebrovascular Disorders↗
PubMed1980

[Studies on the mechanism of secretion of adrenal steroid hormones from adenomas of primary aldosteronism and Cushing's syndrome (author's transl)].

The mechanism of secretion of adrenal steroid hormones from adenomas of primary aldosteronism and Cushing's syndrome was studied in 10 patients with primary aldosteronism and in 3 patients with Cushing's syndrome in in vivo and in vitro experiments. In all of the 10 patients with primary aldosteronism, ACTH stimulated aldosterone secretion from the adenomas more significantly than did angiotensin II and III. DOC and cortisol which were contained in the adenomas were also stimulated more significantly by ACTH than by angiotensin II and III. Responses of the adenomas of Cushing's syndrome to various stimulations were less than those of primary aldosteronism. Secretion of cortisol and aldosterone from the adenomas of Cushing's syndrome was stimulated by ACTH and angiotensin II to a similar degree. From these studies, it seems that secretion of adrenal steroid hormones from adenomas of primary aldosteronism is more sensitive to extradrenal stimulations than that of Cushing's syndrome, and ACTH is the main factor in the control of the secretion of adrenal steroid hormones from the adenomas.

Adenoma↗
PubMed1980

[Studies on angiotensin II receptors in the adrenal glands and in the aorta (author's transl)].

The angiotensin II receptor in the rabbit, rat and human adrenal gland and that in the rabbit and rat aorta were studied by using [3H]-angiotensin II ([3H]-AII). The adrenal glands and the aorta of each species were centrifuged at 20,000Xg for 30 min, and pellets which contained 95% of binding sites were collected and diluted by a buffer [20 mM Tris-HCl buffer (pH 7.4), 120 mM NaCl, 0.2% BSA, 1 mM EDTA] and used as a membrane fraction. The binding study was done by incubating the membrane fraction and [3H]-AII. After incubation at 25 degrees C for 30 min, the binding of the membrane fraction and [3H]-AII reached the equilibrium state, and free and bound angiotensin II were separated by 0.48 micrometer filters. Protein concentration was determined according to the method of Lowry. The binding sites fulfilled the criteria of the receptor which has organ and structure specificities, high affinity and reversibility. We could thus measure angiotensin II receptor in this study correctly and concisely. The properties of the angiotensin II receptor were analysed by Scatchard plot. The number of rabbit adrenal receptors (12833 +/- 2115 x 10(-15) mol/mg.protein) (M ++/- SD) was greater than that of the rat (1780 +/- 166 x 10(-15) mol/mg.protein) and that of the human (356 +/- 124 x 10(-15) mol/mg.protein). But the dissociation constant of all species was the same. The number of aorta binding sites was less than that of the adrenal in rabbits and rats. But the dissociation constant of rabbits and rats aorta binding sites was quite similar to that of adrenal glands.

Adrenal Glands↗
PubMed1980

Effect of microwave irradiation on brain tissue structure and catecholamine distribution.

Recently we reported regional levels of norepinephrine and dopamine in rat brain following microwave irradiation. In our report, we also compared these levels with those of norepinephrine and dopamine following decapitation. Catecholamine levels following exposure to microwave irradiation significantly increased in several areas. However, whether these increases resulted from compound transfer associated with tissue disruption due to high intensity microwave irradiation was not determined. Sections of corpus striatum and locus coeruleus were examined with a light microscope and the interface of the striatum and the cortex showed no trace of tissue breakdown. Transformed cells, vacuolation, and indications of pyknotic degeneration in the nucleus were found in locus coeruleus after irradiation, but the shapes of these cells were well-defined. Electron microscopic photographs of synapses in the same area showed membrane damage after exposure for 5 s at 1.3 kW, but synaptic vesicles were clearly defined. It was concluded that the increased catecholamine levels were not the result of tissue disruption following rapid heating of the brain by irradiation.

Animals↗
PubMed1980

Effects of postural change of the shoulder on EMG reaction time of triceps brachii.

Postural dependence of electromyographic reaction time (EMG-RT) of triceps brachii in normal subjects was examined at neutral (N) and facilitating (F) positions. EMG-RT was faster at F than at N; moreover, the slower one's EMG-RT, the larger the difference of EMG-RTs. F position of arms causes the shifting of EMG-RT through two biasing systems. The action of one system arises from either arm and acts on both arms, as the facilitation and its intensity depend on one's EMG-RT. The other system arises from one arm, and facilitates the ipsilateral arm but inhibits the contralateral arm; its intensity is independent of one's EMG-RT. The amount of the shift is determined by the added contribution of those two actions.

Adolescent↗
PubMed1980

Postural dependence of reaction time after a VL thalamotomy.

Postural dependence of the EMG-RT of the triceps brachii muscles was measured in 68 parkinsonian patients of which 38 underwent a ventrolateral thalamotomy. A thalamotomy did not affect patients' EMG-RT per se, but it changed the postural dependence of the EMG-RT. After left thalamotomy the position changes of both shoulders did not influence the EMG-RT of the right triceps, and after right thalamotomy the position change of the left shoulder had no influence on the EMG-RT of both triceps. As for the sensorimotor function, it is assumed that the right thalamus has bilateral control on the input system and the left thalamus has bilateral control on the output system.

Adult↗
PubMed1980

Purification and characterization of galactosyltransferase in human parotid saliva.

The galactosyltransferase has been purified from human parotid saliva by ammonium sulfate precipitation (25-70% saturation), followed by repeated affinity chromatography on Sepharose-alpha-lactalbumin. The molecular weight of the enzyme was estimated to be approximately 56,000. The enzyme catalyzes the transfer of galactose from UDP-galactose to the exposed N-acetylglucosamine residues derived from glycoproteins, forming a Gal beta (1-4)GlcNAc linkage.

Adult↗