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Biomedical subjects

K Nakayama

Publications and source records attributed to K Nakayama.

At least 19 recordsLinked to original sources
PubMed1979

Kinetic analysis of plasma TSH dynamics after TRH stimulation.

Kinetic analysis of the time course of plasma TSH after TRH stimulation was performed by means of a single compartment model with first order input. This kinetic model showed satisfactory fit to the data, and was found to be useful enough for the characterization of plasma TSH dynamics. In endocrinologically normal short children, the amount of TSH release per unit volume of distribution space (Q0/V), the rate constant for the TSH release (alpha), and the rate constant for TSH elimination (beta) were averaged 23.4 microU/ml, 6.981 hr-1 and 0.813 hr-1, respectively. Elevated Q0/V values with lowered alpha and beta were obtained in the hypothyroid children. Variable results, with the exception of low alpha values, were obtained in the children with pituitary dwarfism.

Adolescent↗
PubMed1979

Impedance cardiography for the assessment of cardiac function during exercise.

1. Impedance cardiography proved valuable to estimate the stroke volume and other cardiac parameters noninvasively, when the electrical resistivity of the blood was corrected with hematocrit. 2. Cardiac response to graded exercise on a bicycle ergometer up to the maximal load in healthy young and active middle-aged subjects was divided into four phases from the changes in cardiac parameters such as stroke volume, cardiac output, ejection index and height of the atrial wave. 3. The ischemic patients did not tolerate well the exercise after the second phase or drift phase of exercise. 4. Physical training enhanced the cardiac function in work through increase in cardiac output and work load.

Adult↗
PubMed1979

Antiarrhythmic activity of dextro- and levo-isomers of 5-methyl-8-(2-hydroxy-3-t-butylamino-propoxy) coumarin hydrocholoride (bucumolol), a beta-adrenergic blocking agent, on aconitine-induced atrial and ouabain-induced ventricular arrhythmias in dogs.

The beta-blocking, antiarrhythmic, and local anesthetic effects of the racemic mixture and optical isomers of bucumolol, 5-methyl-8-(2-hydroxy-3-t-butylamino-propoxy) coumarin hydrochloride, were studied in dogs, guinea-pigs and frogs. In blocking the positive chrontropic response to isoproterenol, the levo-isomer of bucumolol was about 40 times more potent in dogs, and 270 times in guinea-pigs than its dextro-isomer and twice as effective in both species as the racemic mixture. In frog sciatic nerves bucumolol was 1/10-1/15 as potent in local anesthetic action as propranolol on a weight basis. Dextro- and levo-isomers and racemic bucumolol neither elevated electrical threshold for propagated impulses nor prolonged the effective refractory period of the dog right atrium. The levo-isomer and racemic bucumolol were capable of suppressing aconitine-induced atrial arrhythmia, while the dextro-isomer was less effective. Both isomers and racemic bucumolol were capable of reversing ventricular arrhythmia caused by ouabain, but the effective dose of the levo-isomer was significantly less than that of the dextro-isomer. The results suggest that both specific beta-blocking activity and non-specific membrane action of bucumolol suppressed experimental arrhythmias in dogs produced by aconitine and ouabain.

Aconitine↗
PubMed1979

Rapid assessment of visual function: an electronic sweep technique for the pattern visual evoked potential.

We have developed an electronic spatial frequency sweep technique for electrophysiological assessment of visual acuity and pattern vision. The technique allows an accurate and reliable measurement of VEPs to a full range of spatial frequencies in just 10 sec. Because the measurements are so rapid, the technique suggests several new improvements in the assessment of visual function. Sweeping spatial frequency linearly and extrapolating the high-frequency region of the VEP spatial-tuning function to zero voltage allows an estimate of acuity which correlates highly with psychophysical estimates of acuity. Variants of the procedure are appropriate for the assessment of refracture error, determination of equality of visual function for the two eyes and of binocular interactions, and for sequential assessment of therapeutic conditions.

Amblyopia↗
PubMed1979

An endoscopic staining method for detection and operation of early gastric cancer.

The long term survival rate of gastric cancer has been much improved, and the 5-year survival rate in our institute was 42% with a significant difference between 29% in the advanced stage and 94% in the early stage. This result means that gastric cancer must be detected and treated early as possible. However, the diagnosis of early gastric cancer may remain extremely difficult even for an excellent endoscopist. Therefore, in order to clearly recognize early gastric cancer, an endoscopic staining method with methylene blue has been studied. In this method, one capsule of 150 mg methylene blue is swallowed with a small amount of proteinase solution 3 hours before endoscopy. Gastroscopy is performed routinely after this preparation. This procedure was performed on 153 gastric cancers and 137 of them (89.5%) have been successfully dyed in dark blue. In several cases, with this method, the actual borderline between the normal mucosa and the malignant extent was clearly recognized and resection line was decided. Introduction of methylene blue into the stomach could also stain the intestinalized epithelium of the gastric mucosa. Differential diagnosis of the dyed intestinal metaplasia and the dyed carcinoma seems to be very easy, because both gastric lesions have the characteristic dyed patterns. Mechanism of this phenomenon has been considered to be due to an absorption of the dye in the intestinal metaplasia, and in the gastric cancer, many factors may be involved, among which are the infiltration or diffusion of the dye into the cancerous tissue, the absorption from the abnormal epithelium, and the staining of the necrotic tissue.

Adenocarcinoma↗
PubMed1978

Multiple spatial-frequency tuning of electrical responses from human visual cortex.

Human occipital potentials evoked by stimulation with a counterphase flickering grating were recorded by a digital narrowband filter technique. The data showed a surprising degree of narrow tuning to particular spatial frequencies in addition to the expected narrow temporal frequency tuning. At each temporal frequency, there could be two or more peaks of different spatial frequencies, each distinct from the whole field flicker response. Variations in this multiple spatial frequency tuning were investigated as a function of luminance, electrode location, and temporal frequency for several observers. The results are interpreted in terms of many stimulus-specific resonant neural circuits within the brain, and suggest that it is possible to make a highly detailed exploration of the responses of neural circuits to visual stimulation.

Electroencephalography↗