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Biomedical subjects

O Yamada

Publications and source records attributed to O Yamada.

At least 271 records · Page 15Linked to original sources
PubMed1980

Abnormal adherence of sickle erythrocytes to cultured vascular endothelium: possible mechanism for microvascular occlusion in sickle cell disease.

The abnormal shape and poor deformability of the sickled erythrocyte (RBC) have generally been held responsible for the microvascular occlusions of sickle cell disease. However, there is no correlation between the clinical severity of this disease and the presence of sickled RBC. In searching for additional factors that might contribute to the pathophysiology of sickle cell disease, we have investigated the possibility that sickle RBC might be less than normally repulsive of the vascular endothelium. After RBC suspensions are allowed to settle onto plates of cultured human endothelial cells, normal RBC are completely removed by as few as six washes. In contrast, sickle RBC remain adherent despite multiple washes. On subconfluent culture plates, normal RBC are distributed randomly, whereas sickle RBC cluster around endothelial cells. Sickle RBC adherence is not enhanced by deoxygenation but does increase with increasing RBC density. The enzymatic removal of membrane sialic acid greatly diminishes the adherence of sickle RBC to endothelial cells, suggesting that sialic acid participates in this abnormal cell-cell interaction. Although net negative charge appears normal, sickle RBC mainfest an abnormal clumping of negative surface charge as demonstrated by localization of cationized ferritin. These abnormalities are reproduced in normal RBC loaded with nonechinocytogenic amounts of calcium. We conclude that sickle RBC adhere to vascular endothelial cells in vitro, perhaps caused by a calcium-induced aberration of membrane topography. This adherence may be a pathogenetic factor in the microvascular occlusions characteristic of sickle cell disease.

Anemia, Sickle Cell↗
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↗
PubMed1980

Primary intracranial choriocarcinoma.

The authors report four cases of primary intracranial choriocarcinoma, all in young males. There tumors occurred in the pineal region and one in the lateral ventricle. Besides the signs of increased intracranial pressure and ophthalmological disorders, skin pigmentation or eruption was observed in three cases and precocious puberty in two cases. Angiography revealed tumor stain with irregular vessels in all cases. Enhanced computerized tomography scans in the last two cases demonstrated a round, lobulated lesion of high density, with relatively low density in the central portion. Hormonal study was carried out in three cases. In addition to high levels of human chorionic gonadotropin (HCG) in the urine and cerebrospinal fluid and/or of plasma luteinizing hormone (LH), LH in tumor tissue or medium obtained via cell cultures was also high in all three cases, suggesting inherent activity of HCG secretion by the tumor cells. The tumors were relatively demarcated from the surrounding brain. They were very hemorrhagic, and fresh hematoma was identified in the tumor in case. Good results were obtained in two cases treated with surgical removal followed by simultaneous chemotherapy and 60Co irradiation.

Adolescent↗
PubMed1979

Modulation of neutrophil function by lysozyme. Potential negative feedback system of inflammation.

Host responses to infectious organisms should be modulated so that tissue-damaging products of inflammatory cells do not produce excessive destruction of normal tissue. Lysozyme, which is continuously secreted by monocytes, which, in turn, migrate relatively late to inflammatory areas, was found to significantly dampen several responses of neutrophils to inflammatory stimulants. Thus, human lysozyme obtained and purified from the urine of patients with monocytic leukemia (but not its structurally similar and comparably cationic analogue, eggwhite lysozyme) depresses chemotaxis of normal neutrophils to activated complement, bacterial supernate, and N-formylmethionyl-phenylalanine. In addition, human (but not eggwhite) lysozyme depresses oxidative metabolism (hexose monophosphate shunt activity) and superoxide generation of neutrophils. The specificity of the suppressive effects was indicated by inhibition studies with rabbit antihuman lysozyme antibody, and with the trisaccharide of N-acetylglucosamine, a specific inhibitor of lysozyme. The results suggest that lysozyme, a product of inflammatory cells themselves, may function in a negative feedback system to modulate the inflammatory response.

Cell Migration Inhibition↗
PubMed1979

Cochlear distribution of frequency-following response initiation. A high-pass masking noise study.

The cochlear initiation of the frequency-following response (FFR) to 500-Hz tone bursts was assessed in 6 normal-hearing subjects by measuring FFR amplitude as a function of the low-frequency cutoff of high-pass masking noise (3 550, 1 800, 900, and 450 Hz). The major fall off of FFR amplitude occurred when the masking noise began to mask the apical portion of the cochlea. This effect was especially apparent at low intensities. The results are interpreted as supporting the view that at low intensities, low-frequency tone bursts evoke the FFR primarily through the apical portion of the cochlea.

Adult↗
PubMed1979

Effects of rise time on simultaneously recorded auditory-evoked potentials from the early, middle and late ranges.

The view that the effects of stimulus rise time are qualitatively different for early brain stem components, middle latency components and late vertex components of the auditory-evoked responses was reexamined. The amplitudes and latencies of the brain stem response (Jewett's wave V), middle latency components Na and Pa, and vertex potentials P1, N1 and P2, evoked by tone burts of various rise times, were analyzed. Increases in rise time were associated with smaller peak amplitudes and longer peak latencies for all of the components measured. These effects were comparable in magnitude for all the components. The results are interpreted in terms of a delayed and less synchronized neural discharge from the cochlea as rise time is extended.

Adult↗
PubMed1979

Cochlear processes affecting wave V latency of the auditory evoked brain stem response. A study of patients with sensory hearing loss.

The effects of inner ear pathologies on wave V latency of the auditory evoked brain stem response (BSR) were studied in 12 selected patients with flat, low-frequency, severe high-frequency, and gradual high-frequency sensory hearing loss. In patients with flat and low-frequency sensory hearing loss (Meniere's disease), the latencies of wave V at intensities 4--10 dB greater than their response thresholds were roughly the same as those in normal-hearing subjects. In patients with severe high-frequency sensory hearing loss (sharp cut-off at about 2 or 3 kHz), the latencies of wave V were always delayed, compared with those in normal-hearing subjects. In patients with gradual high-frequency sensory hearing loss, the latency of wave V was delayed according to the degree of hearing loss (as determined by pure tone audiometry) above 2 kHz. The data are interpreted as showing that the wave V latency is sensitive to a kind of recruiting phenomenon in the transduction process as well as being an index of the pressure wave travel time to the cochlear portion responsible for the elicitation of the BSR.

Adult↗
PubMed1979

Effect of dietary excess leucine on nicotinamide nucleotide level in rat liver.

1. Six groups of rats were freely fed diets containing casein at 5, 10 and 20% levels with and without nicotinic acid. After 2 weeks on these diets, hepatic nicotinamide nucleotide and free nicotinic acid concentrations were studied. 2. Hepatic nicotinamide nucleotide level was kept in the normal range in rats fed the 10 and 20% casein diets with and without nicotinic acid. 3. L-leucine supplemented at the 5% level to the 10 and 20% casein diets caused significant decrease in hepatic nicotinamide nucleotide level only in rats fed nicotinic acid devoid diet. 4. Hepatic nicotinamide nucleotide in rats fed the diet in which casein was replaced by zein increased significantly by adding nicotinic acid. This increase in the hepatic nicotinamide nucleotide caused by dietary supplemented nicotinic acid was not reduced by the addition of L-leucine. 5. The hepatic free nicotinic acid level did not change even in rats of which hepatic nicotinamide nucleotide was significantly reduced. 6. Urinary excretion of nicotinic acid and N-methylnicotinamide was increased significantly by adding nicotinic acid to the diet but was not affected by adding L-leucine at the 5% level. 7. From the above results, a possible mechanism of L-leucine action was discussed.

Administration, Oral↗
PubMed1979

Granulocyte aggregation as a manifestation of membrane interactions with complement: possible role in leukocyte margination, microvascular occlusion, and endothelial damage.

Activation products of the terminal complement cascade potently affect granulocyte function, inducing, for example, their migration toward (chemotaxis), and adherence to (opsonization), microbes, and stimulating their production of microbicidal oxygen radicals such as superoxide anion, and the like. We present studies that demonstrate that a C5-derived peptide, probably C5a, is a potent promoter of granulocyte and monocyte adhesion to endothelium (margination) and, in addition, causes granulocyte autoaggregation in vitro and in vivo. Although possibly beneficial by producing phagocyte clumps to mechanically entrap unwanted microbes, such aggregates may be deleterious, particularly if sustained, especially in the lung.

Animals↗