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Biomedical subjects

K Kaga

Publications and source records attributed to K Kaga.

At least 199 records · Page 11Linked to original sources
PubMed1980

Application of brain stem response in brain-injured children.

The early components of the auditory evoked potential within 10 msec following an auditory stimulus are attributed to the brain stem auditory nuclei and pathways. In pediatric neurology the auditory brain stem response (ABR) can be applied to: 1) differential diagnosis of hearing impairment in young children including objective threshold measurement of hearing, 2) electrophysiological evaluation of maturation of the auditory pathways, 3) diagnosis of the site and/or extent of neurlogical diseases affecting the brain stem and 4) observation of a degenerating process of degenerative diseases in the central nervous system. The paper is especially concerned with the application of ABR to severe neurological diseases in children including central auditory dysfunction, cerebral palsy, infantile spasm, adrenoleucodystrophy, anoxic brain damage and Down's syndrome. Value and limitation of ABR audiometry in the clinical practice were mentioned, and a special emphasis was placed on the fact that all types of auditory tests including behavioral, electrophysiological, and developmental tests are indispensable, because the ABR, like other indicators, also has its own limitation.

Brain Damage, Chronic↗
PubMed1980

Isolation of Dane particles containing a DNA strand by metrizamide density gradient.

Dane-particle cores labelled with [3H]TTP were subjected to ultracentrifugation in a metrizamide density gradient. Two populations of core particles with different densities were obtained, and radioactivity was found only in the cores that sedimented at the lower density (1.19-1.23 g/cm3). All the cores in this group, when spread in a monolayer, were found to expel a closed circular double-stranded DNA molecule. In contrast, the core particles that sedimented at the higher density (1.23-1.27 g/cm3) were not associated with radioactivity, nor was any DNA strand extruded from them. These results show that metrizamide density gradients allow the separation of complete hepatitis B virions for the study of viral DNA.

Centrifugation, Density Gradient↗
PubMed1980

Immunoelectron microscopic observation of hepatitis B surface antigen on the surface of liver cells from patients with hepatitis B virus infection.

A recently modified method using peroxidase labeled antibodies for light and electron microscopic demonstration of hepatitis B virus (HBV) was applied to the evaluation of hepatitis B surface antigen (HBsAg) on the surface of liver cells in biopsy specimens from 24HBsAg chronic carriers. Membranous distribution of HBsAg was demonstrated in diffuse or scattered hepatocytes in all 4 asymptomatic carriers and in 3 of the 20 patients with HBsAg-positive chronic active hepatitis or liver cirrhosis. In these patients with membranous expression of HBsAg, hepatitis B e antigen, Dane particles and DNA polymerase were often detected in sera, and large amounts of hepatitis B core antigen appeared in the liver. These results suggest that membrane-bound HBsAg may be expressed by the HBV genome. The ultrastructural study of liver cells showing membranous expression disclosed dense deposits of reaction product indicative of HBsAg on the cell membrane and/or on assembled particles within the extracellular space. In some hepatocytes showing both diffuse cytoplasmic and membranous expression of HBsAg, HBsAg-positive membrane of cisternae open to the intercellular space was connected with the liver cell membrane. These findings supported the conjecture that HBV associated antigens are integrated into the liver cell membrane.

Hepatitis B↗
PubMed1980

Binaural interaction of a beating frequency-following response.

Frequency-following responses to 500-Hz tone bursts presented to the left ear and 540-Hz tone bursts presented to the right ear were recorded from human subjects. Recordings were made both under monaural and binaural conditions. The responses summed over monaural conditions (for left and right ear stimulation) were larger than the responses obtained in the binaural condition. This binaural interaction shows that the frequency-following response reflects binaural processing probably occurring at or below the level of the inferior colliculi.

Acoustic Stimulation↗
PubMed1979

Effects of deep hypothermia and circulatory arrest on the auditory brain stem responses.

The effects of hypothermia on auditory brain stem response (ABR) in both children with congenital heart disease undergoing cardiac surgery and cats as an animal model were investigated. The latency of the ABR waves were prolonged with decreased body temperature. The latency of the later response components were prolonged more than that of the earlier response components; all waves disappeared below 25 degrees C and during artificial cardiac arrest. When the body temperature was raised, the later component began to reappear above 25 degrees C; the latency of all components shortened with temperature until normal responses were obtained at 34 degrees C. The data from both humans and cats were comparable. The ABR seems to be a useful monitor for evaluating brain stem function during deep hypothermia.

Animals↗
PubMed1979

The effect of the click repetition rate on the latency of the auditory evoked brain stem response and its clinical use for a neurological diagnosis.

The effects of click repetition rate on the latency of the auditory brain stem responses (BSR) and its possible use as a clinical diagnostic tool of the brain stem disorders were investigated. When the click rate was increased, the latency of the BSR waves was prolonged. The latency of the later response components increased more than that of the earlier response components. This method was applied to the clinical cases with brain stem disorders. A case with a IVth ventricle epidermoid tumor showed a marked latency prolongation and disappearance of the waves at higher repetition rates. An explanation of the latency shift in the normal subjects and the abnormal responses of the patient to repetition rate is attempted.

Acoustic Stimulation↗
PubMed1979

Auditory brain stem responses of kernicterus infants.

Auditory brainstem evoked responses (ABRs) and behavioral audiometry in 25 infants with kernicterus were studied to determine the level of the lesion causing their hearing disorders. ABR thresholds, peak latencies of wave I and V, and interwave latency of wave V-I were measured; behavioral audiometric thresholds were determined through conditioned orientation reflex audiometry (COR). Eighty-eight per cent of infants with kernicterus who showed ABR threshold elevation with respect to age-matched normals, were found to show ABR abnormalities associated with peripheral hearing loss, and 84% of these were found to have COR threshold elevation. The ABR abnormalities were threshold elevation of wave V, prolonged latency of wave I and V, and the absence of ABRs. However, no brainstem lesion pattern was found in our cases. Our results suggested that at least some lesions which produce hearing disorders in kernicterus occur in the cochlea or auditory nerve.

Adolescent↗
PubMedDate not supplied

Auditory 40-Hz responses in the guinea pig.

Auditory evoked potentials in response to tone bursts repeated at a rate of 40 per second (auditory 40-Hz responses) were studied in the guinea pig. The potentials, consisting of a sequence of 40-Hz waves with a periodicity of about 25 msec, were distributed widely over the skull, and the largest potentials were recorded from the vertex (midline) and the temporal area contralateral to the stimulated ear. Administration of pentobarbital did not affect the midline response but reduced the amplitude of the contralateral response. Investigations of the effects of acute lesions demonstrated that the auditory 40-Hz responses from the contralateral temporal area were eliminated by aspiration of the contralateral cerebral cortex, whereas the responses from the midline continued to appear after bilateral aspiration of the cerebral cortex. The response from the midline was maintained after bilateral aspiration of the inferior colliculi, and the basic 40-Hz rhythm was still observed after decerebration. These data suggest different generation areas for the midline and contralateral 40-Hz responses in the guinea pig.

Acoustic Stimulation↗