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Biomedical subjects

S Usui

Publications and source records attributed to S Usui.

At least 163 records · Page 9Linked to original sources
PubMed1984

[Adjustment of urinary delta-aminolevulinic acid concentrations in workers exposed to lead and heat. Adjustments of specific gravity to 1.020 and urinary volume coefficients].

Adjustments of urinary ALA concentrations as to urinary specific gravity and creatinine were examined for workers exposed to lead and heat. Judging from our findings, we suggested that it was preferable to adopt the specific gravity (UG) at 1.020 as the adjustment value to obtain the correct urinary ALA concentration. Though corrected values thus obtained were found adequate for urine in the normal range of specific gravity, they failed to be adequate for concentrated urine samples higher than UG 1.025. Urinary volume adjustment was found to be necessary for these concentrated urine in stead of urinary specific gravity adjustment. For the practical purposes, we postulated urinary volume coefficients, which were estimated to be 0.5 for samples ranging from UG 1.026 to 1.030, 0.4 for samples from UG 1.031 to 1.035 and 0.3 for samples from UG 1.036 to 1.040, respectively.

Aminolevulinic Acid↗
PubMed1983

Discrete nonlinear reduction model for horizontal cell response in the carp retina.

In this paper we present a new model for the spatial behavior of the external horizontal cells in the carp retina which elucidates more precisely the mechanisms of their intercellular connections. The area and intensity effects of a brief light stimulus on the L-type response were recorded and analysed. We discovered clear nonlinearities in the behavior of the response which could not be explained by the simple summative model presently accepted. Proposed here is a new model, the spatial reduction mechanism, which explains the experimental evidences including these nonlinearities. We also present the results of a computer simulation using our new model in parallel with the actual results obtained experimentally. The physiological implications of these findings are discussed.

Animals↗
PubMed1983

[Effects of fornix lesion on visual evoked responses during sleep and wakefulness in rats].

The effects of fornix lesion on visual evoked responses (VERs) recorded from the occipital cortex (OCX) and the lateral geniculate body (LGB) were examined during wakefulness (W), slow wave sleep (SWS) and paradoxical sleep (PS) respectively, in freely moving rats (N = 6). In intact animals, amplitudes of VERs changed with sleep-waking stages in a decreasing order of SWS, PS and W. After fornical lesion, mean amplitudes of VERs were significantly enhanced at OCX, but not at LGB. As to OCX, amplitudes of early components of VERs increased during all sleep-waking stages, and those of later components increased only during sleep. These results suggest that the fornix system exerts some modulatory (probably inhibitory) influence on OCX in close relations to sleep-waking stages in rats.

Animals↗
PubMed1982

Sleep-waking rhythm altered by 2-hour light phase access to food in the rat.

The effects of 2-h restricted feeding (RF, 10.00-12.00 h) on sleep rhythms were examined in 9 male rats on a 12:12 h LD cycle (L 08.00-20.00 h). During the third week of RF, sleep amounts showed a striking reduction during a 4-h period (08.00-12.00 h), and LD differences in SWS and PS amounts were markedly reduced. Hourly sleep amounts showed a bimodal distribution during a 24-h day. Analyses of periodicity of SWS and PS occurrences revealed a dominant 12-h periodicity and a relative diminution of the 24-h one. The appearance of a 12-h rhythm of sleep may be due to an interaction of the two zeitgebers (LD cycles and restricted feeding) and possibly to the timing of RF.

Animals↗
PubMed1982

A model for nonlinear stochastic behavior of the pupil.

In this paper we present new experimental results that show pupillary noise to be multiplicative in a particular fashion with greatest variance in midrange and smaller variance at high and low ranges. This confirms the finding of multiplicative noise by Stanten and Stark (1966), but modifies and extends the relationship they suggested between standard deviation and mean pupil diameter. We propose a parametric model of the iris muscle which not only describes the static characteristics of pupil response to given stimuli, but also explains its random fluctuations in terms of probability density functions. We emphasize the point that the range nonlinearity is not due to decreased gain at the extrema of the pupil range, but is operational over a wide portion of the pupillary behavioral range, hence its name--"expansive range nonlinearity". We conclude that noise amplitude, which is a function of the pupil diameter, closely parallels the changes in deterministic gain. Thus pupil noise can be simply considered as cross-talk additive Gaussian noise injected into the pupil system at midbrain level.

Humans↗
PubMed1981

Electroencephalographic analysis of activities in the optic tectum of unrestrained carp.

Electroencephalographic activity of the optic tectum in unrestrained resting carp was classified into three dominant frequency ranges of 4-7, 8-13 and 14-25 HZ, peaking at 6, 10, and 17 and 22 HZ, respectively, under power spectral analysis. All these activities were suppressed in the dark. The suppression was most prominent in the 8-13 HZ waves, but less so in the 4-7 HZ. However, while the fish was swimming actively, the 4-7 HZ spectrum increased in power and no actual increase could be observed for the higher frequency waves. Thus, it is probable that the 4-7 HZ waves involve rich motor activity, while the 8-13 HZ waves are mainly visual. The tectal activity was enhanced in the hypoxic state, with an increase in all frequency components, and enhanced further after loading, each of which corresponds to the hypoxic and post-hypoxic activations described for the mammalian cortex. A component analysis for the photically evoked response in restrained carp supported the four peaks of fundamental tectal rhythm being obtained as the spontaneous activity. In addition, each component belonging to the lower two peaks could be decomposed into the others, suggesting that the 17 and 22 HZ waves might be elementary for the tectal activity.

Animals↗
PubMed1981

Microsomal reductase for aromatic aldehydes and ketones in guinea pig liver. Purification, characterization, and functional relationship to hexose-6-phosphate dehydrogenase.

An NADPH-specific aromatic aldehyde-ketone reductase located in guinea pig liver microsomes can be effectively solubilized with nonionic detergents, but not with bile salts and hydrolytic enzymes. Destruction of microsomal membranes by nonionic detergents or acetone treatment leads to significant activation of the reductase, indicating that the enzyme is partly latent in intact microsomes. After solubilization with Triton X-100, the reductase has been highly purified. The purified enzyme catalyzes the NADPH-linked reduction of xenobiotic aromatic aldehydes and ketones as well as 3-ketosteroids, notably 5 alpha- and 5 beta-dihydrotestosterones. The reductase activities for xenobiotic carbonyl compounds and for 3-ketosteroids are each inhibited by addition of the other type of substrate and show the same pH optimum, cofactor requirement, and heat stability, indicating the same enzyme is responsible for the reduction of the two types of substrates. Hexose-6-phosphate dehydrogenase, purified from guinea pig liver microsomes, acts as a more effective NADPH generator for the reductase than yeast and guinea pig liver cytosolic glucose-6-phosphate dehydrogenase. Evidence has been obtained that hexose-6-phosphate dehydrogenase undergoes a functional interaction with the reductase, facilitating the provision of NADPH to the reductase activity both in the reconstituted system and in microsomes.

Alcohol Oxidoreductases↗
PubMed1979

Growth-stimulating factor in regenerating canine liver.

Extracts from dog livers which had been regenerating for 24, 48, and 72 h after hepatectomy were infused for 6 h into the left portal vein of animals which had fresh portacaval shunts (Eck fistula) and which were killed 2 and 3 days later. The brief exposure to the 48-h and especially the 72-h regenerating liver extracts induced a delayed proliferative response predominantly in the left liver lobes, with a slight spillover effect to the right liver lobes but none to the kidney. The response reached its peak 3 days later. In the left but not the right liver lobes, both the 48-h and the 72-h regenerating liver extract reversed the atrophy ordinarily caused by Eck fistula in 3 days and partly prevented the ultrastructural hepatocyte deterioration characteristic of Eck fistula. The active liver extracts apparently contained a growth-control factor or factors which is (are) not insulin or glucagon.

Animals↗
PubMed1979

Branched chain amino acid administration and metabolism during starvation, injury, and infection.

Branched chain amino acids were administered intragastrically in a septic-fractured rat model to determine the degree and mechanism of their protein-sparing ability. The septic injury model was first shown to produce a metabolic response characterized by hyperglycemia, reduced ketonemia and increased nitrogen loss. Branched chain amino acids were then administered either alone or as 25% or 50% (w/w) of a complete crystalline amino acid solution. L-(U-14C)-tyrosine was added to the diet to estimate protein synthesis in individual tissues. Branched chain amino acids, when given alone, spared total body nitrogen as compared with fasting by increasing the fractional synthesis of both mixed liver and muscle protein. Although the two complete amino acid mixtures produced similar nitrogen preservation and muscle synthesis in the septic animals, the crystalline amino acid diet containing 50% branched chain amino acids resulted in the greatest preservation of total liver nitrogen and the highest fractional synthetic rate. The effect of branched chain amino acids would not appear to be explained by their nitrogen content alone, and in starvation with injury and infection, increased intakes may have potential benefit. Clinical trials in starved, injured man appear to be indicated.

Amino Acids, Branched-Chain↗