Search PubMed⌕ Search

Biomedical subjects

Y Komai

Publications and source records attributed to Y Komai.

At least 19 recordsLinked to original sources
PubMed2006

Evaluation of nutrient loads from a mountain forest including storm runoff loads.

Water quality and flow rates at a weir installed on the end of Aburahi-S Experimental Watershed (3.34 ha) were measured once a week from 2001 to 2003 and in appropriate intervals from 30 min to 6 h during five storm runoff events caused by each rainfall from 8 mm to 417 mm. The average annual loads of total nitrogen (TN) and total phosphorus (TP) were calculated to be 19.0 and 0.339 kg ha(-1) y(-1) from the periodical data by using the integration interval-loads method (ILM), which did not properly account for storm runoff loads. Three types of L(Q) equations (L = aQ(b)) were derived from correlations between loading rates L and flow rates Q obtained from the periodic observation and from storm runoff observation. L(Q) equation method (LQM), which was derived from the storm runoff observation and allowed for the hysteresis of discharge of materials, gave 9.68 and 0.159 kg ha(-1) y(-1), respectively, by substitution of the sequential hourly data of flow rates. L(R) equation (L = c(R - r)d) was derived from the correlations between the loads and the effective rainfall depth (R - r) measured during the storm runoff events, and L(R) equation method (LRM) calculated 9.83 +/- 1.68 and 0.175 +/- 0.0761 kg ha(-1) y(-1), respectively, by using the rainfall data for the past 16 years. The atmospheric input-fluxes of TN and TP were 16.5 and 0.791 kg ha(-1) y(-1).

Atmosphere↗
PubMed2002

Application of an automatic sampling and measurement system to a mountainous stream investigation during rain events.

An automatic sampling and measurement system was developed to take water samples efficiently during rain events. The system consisted of an automatic sampler, a rain gauge and a data logger as well as sensors for pH, electrical conductivity (EC), and both water and air temperature. The system was tested in a stream in a forested watershed (5.8 km2) located in the middle of Hyogo prefecture, Japan. The sampling program has been improved gradually. For several rain events of 30 to 157 mm, most water samples were in agreement with the hydrograph from the beginning of each rainfall until the rain had stopped and the water level had begun to fall. The fluctuations in water quality in the samples taken by the automatic sampler during those rain events showed patterns similar to those of water samples taken by hand. There were also no problems with the water level or the EC sensor during the investigation periods, but the pH values were lower than those in the laboratory. The results showed that the system is suitable for taking water samples from mountainous streams during rain events.

Altitude↗
PubMed2001

Direct measurement of oxygen partial pressure in a flying bumblebee.

The gas transport system of a bumblebee was investigated by measuring the oxygen partial pressure P(O(2)) in the wing muscle. In the resting bee, P(O(2)) showed a regular pattern of fluctuation with a typical period of 70-120s. Fluctuations in muscular P(O(2)) were associated with intermittent abdominal pumping. Ventilation by abdominal movements may not be necessary during rest because P(O(2)) is high (8.5-9.2kPa) in the anaesthetised bee. Thermal effects on muscular P(O(2)) were examined by cooling the bee, causing the amplitude of P(O(2)) fluctuations to increase. In most flight experiments, the bee started to fly after elevating muscle P(O(2)) by abdominal pumping; muscle P(O(2)) then decreased at the onset of flight. However, when a flight began without pre-flight ventilation, P(O(2)) increased monotonically. During flight, muscle P(O(2)) reached a mean level (6.36+/-1.83kPa) that was much higher than the lowest value recorded during discontinuous ventilation during rest. The bumblebee effectively uses abdominal movements to assist in convective gas transport not only during flight but also at rest.

Animals↗
PubMed2001

Runoff characteristics of nutrients in the forest streams in Hyogo Prefecture, Japan.

Nutrients and other pollutant runoffs from streams in artificial forest areas in central Hyogo Prefecture in southwest Japan have been investigated to estimate pollutant loads since 1995. The orthophosphate and ammonium nitrogen contents were usually low and constant during the investigation. When the flowrates of the streams were normal, the concentrations of suspended solids, COD(Mn), TOC and total phosphorus were very low, and did not change much. However, when stream flows were increased by rainstorms or other precipitation, higher concentrations of these parameters occurred. Otherwise, the average concentrations of nitrate nitrogen and total nitrogen were 0.26 mg/l and 0.31 mg/l, respectively, and they were often increased by precipitation events. They changed at the same time because the ratio of nitrate nitrogen per total nitrogen was high, about 80%. The fluctuation of concentrations of total phosphorus was similar to SS concentrations, which suggested that phosphorus was discharged in the types of suspended solids from forest areas. The specific loads of the nutrients and some other pollutants did not differ among the three watersheds investigated. However, the difference among them between fine days and rainy days was fairly large. It was presumed that pollutant runoff from forest areas is strongly dependent on precipitation events.

Agriculture↗
PubMed2000

Microcoaxial electrode for in vivo nitric oxide measurement.

Nitric oxide (NO) is a gaseous mediator involved in various physiological phenomena, such as vasorelaxation and neurotransmission. Investigation of local cellular responses of NO production in vivo and in vitro requires a measurement method with a high spatial resolution. For selective NO measurement, we therefore developed a microcoaxial electrode whose tip diameter is less than 10 microm. Calibration using various concentrations of NO (0.1-1.0 microM) showed that the electrode has good linearity (r = 0.99) and its detection limit is 0.075 microM (S/N = 3). We verified the applicability of this electrode to in vivo and in vitro local measurement NO released from bovine aortic cultured endothelial cells (BAECs) stimulated by acetylcholine (ACh). After the addition of ACh, a transient increase in NO concentration was detected by the electrode. In the presence of NG-nitro-L-arginine methyl ester (L-NAME), a putative NO synthase inhibitor, NO release (peak NO concentration) from RAECs was significantly less than that in the absence of L-NAME (0.18 +/- 0.04 microM vs 0.47 +/- 0.13; P < 0.01). After removal of L-NAME, NO release partially recovered (0.39 +/- 0.10 microM). In conclusion, the microcoaxial electrode was successfully applied to direct and continuous NO measurement in biological systems.

Calibration↗
PubMed1998

Augmented respiration in a flying insect

The properties of the gas transport system in a tethered flying insect were investigated by directly measuring the oxygen partial pressure (PO2) in a wing muscle of the sweet potato hawkmoth Agrius convolvuli using a needle electrode. At rest, a distribution of PO2 corresponding to levels in the muscle and tracheal structures was observed. At the onset of tethered flight, PO2 in the muscle decreased. However, during a long stable flight, PO2 increased and reached a plateau approximately 2 min after the onset of flight. During stable tethered flight, PO2 in the centre of the second layer of the dorsal longitudinal muscle was locally higher than that during rest. As wing amplitude increased, PO2 increased in spite of the concurrent increase in metabolic rate. During tethered flight at a constant wing amplitude, PO2 was proportional to the mean wing positional angle. The results suggest that this insect effectively uses muscle movement, which increases the frequency and stroke volume of ventilation, to augment gas exchange during flight.

Journal Article↗
PubMed1996

[Two cases of Aspergillus endocarditis after cardiac surgery in childhood].

Aspergillus endocarditis has been considered as a fatal disease because of the difficulty of diagnosis and treatment. Two cases of Aspergillus endocarditis after congenital cardiac surgery are reported. One case was 5-year-old boy after patch closure of atrial septal defect and enlargement of porcine-pericardial patch to pulmonary arterial stenosis. Pulmonary arterial patch infection with vegetation occurred 13 months after operation, and he underwent pulmonary arterial reconstruction with E-PTFE patch after complete removal of porcine-pericardial patch. The other case was 5 year-old girl after repair of tetralogy of Fallot with autologus pericardial monocusp patch. Right ventricular outflow patch infection and mediastinitis occurred 14 months after operation. Although three times of the patch exchange, patch infection relapsed. Therefore, she underwent thorough curettage of infected tissue, and extra-anatomical bypass to bilateral pulmonary artery from right ventricle with E-PTFE Y-graft. The relapse of endocarditis has not been recognized after these surgical treatments in both patients.

Antifungal Agents↗
PubMed1991

The three-dimensional organization of collagen fibrils in the human cornea and sclera.

The organization of collagen fibrils in the human cornea and sclera was studied by scanning electron microscopy, after digestion of cellular elements by sodium hydroxide, and by conventional transmission electron microscopy. The collagen fibrils in the cornea had a uniform diameter of about 25 nm. In Bowman's layer, individual collagen fibrils were interwoven densely to form a felt-like sheet. In the stroma, most of the collagen fibrils ran abreast in lamellae, with varying widths and thickness. These lamellae were arranged basically parallel to the corneal surface but often communicated with those of adjacent layers by interchanging their fibrils. In the innermost stromal region adjacent to Descemet's membrane, collagen fibrils were oriented in various directions and interlaced, forming loose fibrillar networks. The sclera, however, was composed of collagen fibrils with various diameters ranging from 25-230 nm. Although these collagen fibrils formed bundles, they were not parallel but were entangled in individual bundles. These collagen bundles varied in width and thickness, often gave off branches, and intertwined with each other.

Aged↗
PubMed1990

[Measurement of abundance ratio of 15N in amino acids by capillary gas chromatography-mass spectrometry].

A capillary gas chromatography-mass spectrometry for analysis of 15N-labeled amino acids and amides is described. The method is based on direct silylation of amino acids and amides with MTBSTFA and the formation of the TBDMS derivatives. The method was possible simultaneously to measure the 15N abundance ratio of amino-N and amide-N of amides, as to analysis of amino acids.

Amino Acids↗
PubMed1980

A novel sphingophosphonoglycolipid containing 3-O-methylgalactose isolated from the skin of the marine gastropod Aplysia kurodai.

A novel sphingophosphonolipid was isolated from the skin of a marine gastropod, Aplysia kurodai. It was composed of one mol each of sphingosine base, fatty acid, glucose, galactosamine, and an unknown sugar and two mol each of galactose and aminophosphonic acid. The unknown sugar was identified as 3-O-methylgalactose by GC-mass spectrometry of the alditol acetate derivative and by GLC of the trimethylsilyl methylglycoside derivative. The aminophosphonic acid was identified as 2-aminoethylphosphonic acid by TLC of the free acid and the dinitrophenyl (DNP-) compound and by GLC of the O-di-trimethylsilyl-N-isothiocyanate compound. Thus, a ceramide bis(2-aminoethylphosphono)-pentaoside structure having an oligosaccharide chain consisting of one mol each of glucose, 3-O-methylgalactose and galactosamine and two mol of galactose was proposed.

Aminoethylphosphonic Acid↗
PubMed1975

Studies on neuronal lipid.

The procedure for bulk preparation of nerve-cell perikarya from pig brain-stem is briefly described. This method has definite merits with regard to the preservation of the intracellular structures as well as the preservation of the processes. The chemical composition of the isolated nerve-cell perikarya is presented. The nerve-cell perikarya are characterized by the absence of cerebroside and sulfatide. Diffuse distribution of ganglioside on the cell surface is suggested. The lipid content of the nerve-cell perikarya isolated by different methods is discussed. Lipid composition of the invertebrate nervous tissue is discussed. The submicrosomal membranes of rat brain are isolated, and their chemical and morphological properties are discussed. Ribosome-free membranes are characterized by the high content of glycolipids including gangliosides, as well as by the high activity of Na, K-ATPase, whereas ribosome-bound membranes are characterized by the absence of glycolipids, as well as by the low activity of Na, K-ATPase. The molecular organizations of lipid in submicrosomal membranes are demonstrated.

Adenosine Triphosphatases↗