Search PubMed⌕ Search

Biomedical subjects

Y Ooi

Publications and source records attributed to Y Ooi.

At least 19 recordsLinked to original sources
PubMed2004

Velocity pulse advances pressure pulse by close to 45 degrees in the rat pial arterioles.

In order to clarify the phase relationship between velocity pulse and pressure pulse propagating along microvessels, the red cell velocity and intravascular pressure were simultaneously measured in the rat pial arterioles of 41-53 microm in diameter with a high temporal resolution by a laser-Doppler anemometer and a servo-null micropressure system. It was found that the velocity pulse preceded the pressure pulse in all the measured arterioles by 18.7-35.6 ms. The corresponding phase difference was 43.6+/-6.9 degrees (mean +/- SD), which is not statistically different from 45 degrees. The value is consistent with the phase difference predicted for the blood flow in microvessels with a small reflection coefficient at frequencies as low as the heart rate of the rats. The present results suggest that the upstream changes in blood flow are transmitted by the velocity pulse faster than by the pressure pulse in the microvasculature.

Animals↗
PubMed1999

Morphine prevents peroxynitrite-induced death of human neuroblastoma SH-SY5Y cells through a direct scavenging action.

N-ethyl-2-(1-ethyl-2-hydroxy-2-nitrosohydrazino)-ethanamine (NOC12), a nitric oxide donor, 3-morpholinosydnonimine (SIN-1), a generator of peroxynitrite (ONOO-), and peroxynitrite induced cell death accompanied by DNA fragmentation in human neuroblastoma SH-SY5Y cell cultures. Morphine prevented the cell death induced by SIN-1 or peroxynitrite, but not that induced by NOC12. The protective effect of morphine was concentration-dependent (10-100 microM), but was not antagonized by naloxone. The selective ligands for opioid receptor subtypes, [D-Ala2, N-Me-Phe4, Gly-ol5]enkephalin (DAMGO, micro-opioid receptor agonist), [D-Pen2,5]enkephalin (DPDPE, delta-opioid receptor agonist) and trans-(+/-)-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]-cyclohexyl)benze neacetamide (U-50488, kappa-opioid receptor agonist) even at the concentration of 100 microM did not prevent the cell death induced by SIN-1. From measurement of the absorbance spectrum of peroxynitrite, the decomposition of peroxynitrite in 0.25 M potassium phosphate buffer (pH 7.4) was very rapid and complete within seconds. However, the absorbance was very stable in the presence of morphine. In addition, morphine inhibited peroxynitrite-induced nitration of tyrosine in a concentration-dependent manner. These results indicate that morphine rapidly reacts with peroxynitrite. The present study showed that morphine prevented peroxynitrite-induced cell death through its direct scavenging action, suggesting that morphine can protect cells against damage caused by peroxynitrite.

Cell Death↗
PubMed1999

A survey of white line disease in Japanese racehorses.

A survey was carried out into white line disease in 1781 Thoroughbred racehorses kept in stables at the Japan Racing Association (JRA) Miho Training Center (MTC) September-October 1996. The survey was conducted while horses were being shod by farriers. The horses that still exhibited damaged white lines after regular trimming were diagnosed as having white line disease. The factors recorded were age, sex, number of diseased horses, number of diseased hooves, number of lesions by region over the bearing border of the hoof and the classified length of such lesions. The percentage of total diseased horses was 11.5% (204 animals), with incidence increasing significantly with age (P< or =0.01). Occurrence was independent of sex (P>0.05) was more frequent in the fore- than in the hindhoof and developed more frequently at the toe than at any other region of the forehoof-bearing border. Most lesions ranged from 20 to 30 mm in length.

Animals↗
PubMed1998

Lipopolysaccharide (LPS) stimulates the production of tumor necrosis factor (TNF)-alpha and expression of inducible nitric oxide synthase (iNOS) by osteoclasts (OCL) in murine bone marrow cell culture.

Osteoclasts (OCL) resorb bone. They are essential for the development of normal bones and the repair of impaired bones. The function of OCL is presumed to be supported by cytokines and other biological mediators, including tumor necrosis factor (TNF)-alpha and nitric oxide (NO). Bacterial lipopolysaccharide (LPS) is a potent inducer of TNF-alpha and inducible nitric oxide synthase (iNOS), which is the specific enzyme for synthesizing NO from L-arginine. To obtain direct evidence on LPS-induced TNF-alpha production and iNOS expression by OCL, OCL-enriched cultures were prepared by 7-day cocultures of bone marrow cells of adult BALB/c mice and osteoblastic cells (OBs) derived from calvaria of newborn BALB/c mice, and the generation of TNF-alpha and iNOS in OCL stimulated with LPS was examined immunocytochemically. When the cultured cells were stimulated with 100 ng/ml of LPS, OCL clearly showed TNF-alpha and iNOS expression. Without LPS-stimulation, no expression was observed. TNF activity in the culture supernatants of the OCL-enriched cultures in the presence of LPS was also detected by cytotoxic assay that used TNF-sensitive L929 cells. The dentin resorption activity of OCL was estimated by area and number of pits formed on dentin slices, which were covered by the OCL fraction and cultured in the presence or absence of LPS, sodium nitroprusside (SNP; a NO generating compound), N(G)-monomethyl L-arginine acetate (L-NMMA; a competitive inhibitor of NO synthase (NOS)), or LPS plus L-NMMA. Pit formation was obviously inhibited in the presence of SNP and slightly inhibited in the presence of L-NMMA, but it was not affected in the presence of LPS or LPS plus L-NMMA. These findings indicate that OCL produces TNF and expresses iNOS in response to LPS, but the LPS-activation of OCL scarcely affects pit formation by them.

Animals↗
PubMed1996

[Selective epidural nerve root block using a superfine fiberscope].

A 65 yr-old male with severe scar pain on his right lower abdomen underwent selective nerve block through epidural space using a superfine fiberscope. A12-gauge Tuohy needle (internal diameter 2.2 mm) was inserted at the intervertebral space of Th12-L1. The fiberscope (external diameter 1.1 mm) was introduced through the needle and the epidural space was observed. When the dura mater of Th12 nerve root level was seen, the patient had pain on the scar area. Then 2% lidocaine 1.5 ml and 60% megumine sodium amidotrizoate 1.5 ml were slowly injected. Soon after injection of anesthetic, analgesia area (Th11-L1) was obtained, and Th12 nerve root was identified by X ray. Epidural blockade using a superfine fiberscope seems to be one of the useful and reliable methods for the selective nerve blockade.

Aged↗
PubMed1995

Measurement of muscle strength of the trunk and the lower extremities in subjects with history of low back pain.

STUDY DESIGN: Isokinetically measured muscle strength of the trunk and lower extremities was analyzed. OBJECTIVES: The causes of the weak trunk muscle strength of subjects with low back pain were studied. SUMMARY OF BACKGROUND DATA: Although it is a commonly accepted conclusion that subjects with low back pain have weaker trunk muscles than the normal population, there are no reports concerning muscle strength of the lower extremities in subjects with low back pain. METHODS: Ninety-eight male volunteers were divided into control groups and groups with low back pain. The total trunk strength and total knee strength were defined as the sum of the peak torques of trunk extension, flexion and rotation, and of bilateral knee extension and flexion, respectively. RESULTS: The total trunk and knee strength in the group with low back pain (281 +/- 170 and 301 +/- 132 Nm) were significantly lower than in the control group (543 +/- 124 and 441 +/- 123 Nm). The total trunk and knee strength were linearly correlated in both groups (r = 0.67 and 0.79). CONCLUSIONS: In the group with low back pain, the muscles of the trunk and the lower extremities were similarly affected; this can be attributed to generalized muscular weakness or psychologic factors, such as fear of injury.

Adolescent↗
PubMed1994

[An experimental study on muscle regeneration--formation of myotubes and environment].

The repair of injured muscle is completed by a proliferation and differentiation of myogenic cells and myotubes. However, little is known about the microenvironment in which the formation of myotubes can proceed in vivo. We employed the polyvinyl alcohol (PVA) sponge model to investigate the milieu in which myotubes could be differentiated. Small pieces of PVA sponge were implanted after immersion in physiological saline into the gastrocnemius of adult Wistar rats as controls. In the experimental groups, before implantation, PVA were treated with basic fibroblast growth factor (FGF), type IV collagen, laminin and hydrocortisone. Newly-formed tissues within the PVA were examined immuno- and histochemically under light- and electronmicroscopy after 7 to 10 days implantation. Particular attention was focused on the formation of myofilaments in the migrating cells. From this study, it became clear that FGF, collagen and laminin accelerated the migration of mesenchymal cells into the PVA compared with controls. However, myotube formation could not be detected in either the experimental or control groups. But in the specimen treated with 10mg/ml hydrocortisone, myotubes appeared frequently in the migrating cells of PVA. A small amount of fibroblasts, macrophages and eosinophils were scattered around the myotubes and not clustered. They were provided with undefined basal lamina. Fibronectin and collagen fibers were also detected surrounding the myotubes. These findings suggested that, although the migration of satellite cells and the appearance of fibronectin are prerequisites for myotube formation, the most promising condition for myotube formation involved a suppression in the migration of the fibroblasts, macrophages and eosinophils. A certain concentration of steroids can therefore prepare a favorable microenvironment for this process.

Animals↗
PubMed1993

(D-Ala, D-Leu) enkephalin reduces the binding of GTP in hippocampal membranes.

The effect of (D-Ala, D-Leu) enkephalin (DADLE) on the binding of GTP in hippocampal preparations was studied. It was observed that treatment of hippocampal slices with 10(-5) -5 x 10(-5) M DADLE followed by the preparation of membrane fractions reduced the binding of 35S-GTP-gamma-S. There was no change in the affinity of the binding. This decrease of 35S-GTP-gamma-S binding was reversed when 5 x 10(-5) M naltrindole was included. The effect was not observed when the membrane fractions were incubated with DADLE. Photoaffinity labeling with the use of 32P P3-(4-azidoanilido)-P1 5'-GTP followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography revealed the incorporation of radioactivity into molecular mass of the 43 kDa and 33-34 kDa proteins. 32P Photolabeling of both the 43 kDa and 33-34 kDa bands decreased following treatment of hippocampal slices with 10(-4) M DADLE. These results suggested that DADLE reduces the GDP-GTP exchange in hippocampal membranes.

Affinity Labels↗
PubMed1991

Serotonin inhibits release of substance P evoked by tooth pulp stimulation in trigeminal nucleus caudalis in rabbits.

The influence of the serotonin (5-HT) system on the release of immunoreactive substance P after electrical stimulation of the lower incisor pulp was examined by perfusion of the superficial layers of the subnucleus caudalis of the brain stem trigeminal sensory nuclear complex of rabbits in situ. Increased release of immunoreactive substance P was observed after electrical stimulation of the pulp at 40 V. Stimulation of the nucleus raphe magnus significantly increased the release of 5-HT and completely inhibited the release of immunoreactive substance P, evoked by stimulation of the tooth pulp. Local application of 5-HT (10(-6) M) inhibited the release of immunoreactive substance P induced by stimulation and this inhibition was antagonized by methysergide (10(-4) M) applied concomitantly to the superficial layers of the trigeminal nucleus. These results suggest a functional interaction between substance P and 5-HT in the superficial layers of the trigeminal nucleus for regulation of transmission of dental pain.

Animals↗
PubMed1991

A study on the surface strain distribution on the hydroxyapatite-implanted canine tibia: a preliminary report.

It has been said by many investigators that hydroxyapatite ceramics may be prospective bone substitute materials. Its mechanical brittleness and strength has been the most serious consideration. In the present article a study has been done using animal experiments, the changes of surface strain at the hydroxyapatite implantation site of long-bone when the compressive stress is applied in the direction of long axis, in order to clarify the mechanical behaviors of hydroxyapatite living bone complex. The nonimplanted side was used as the control. Results revealed that the hydroxyapatite living bone complex has been proven to have sufficient flexibility such that it shows no hysteresis in stress versus strain relation up to 200 kg of applied load. The strain distribution pattern on the HA-implanted bone is quite similar to that of the nonimplanted one. This characteristic also suggests that it has normal skeletal function.

Animals↗
PubMed1990

Modification of the Wagner lengthener to permit dynamic axial loading.

The Wagner lengthener is mechanically excellent, but it lacks a function allowing dynamic axial loading (dynamization), which stimulates bone consolidation at the lengthened section. The authors devised a simple metal insert with which they modified the Wagner lengthener to permit dynamization. The modified appliance was successfully used in two patients.

Achondroplasia↗
PubMed1990

Myeloscopic study on lumbar spinal canal stenosis with special reference to intermittent claudication.

Twenty-five cases of lumbar spinal canal stenosis were investigated by dynamic myeloscopy to explain the pathophysiologic mechanism of intermittent claudication, one of the characteristic signs of the disorder. Myeloscopic examination revealed that, in accordance with postural alteration, the diameter of blood vessels on the cauda equinae showed significant changes in many patients in the stenosis group, but showed no changes in control group. In this series, it was suggested that the microcirculatory disturbance of vessels on cauda equinae might play an important role in the development of intermittent claudication.

Adult↗
PubMed1990

[Effects of 7 drugs on cutaneous blood flow evoked by electric stimulation of rat sciatic nerve].

The non-invasive technique of laser-Doppler flowmeter (LDF) was used to measure the change of cutaneous blood flow evoked by electric stimulation of rat sciatic nerve. The sciatic nerve was cut centrally and placed on bipolar electrodes. Drug were infused in a carotid artery. Electric stimulation of the sciatic nerve containing sensory afferent fibers caused an increase in cutaneous blood flow. This increase was not modified by the ia infusion of adrenergic blocking agents (phentolamine, 0.1 mg/kg and propranolol, 0.5 mg/kg), anti-muscarinic agent (atropine 0.5 mg/kg), anti-histamines (mepyramine, 10 mg/kg and cimetidine, 10 mg/kg) and 5-HT antagonist (methysergide, 0.5 mg/kg). Pretreatment with capsaicin (50 mg/kg, sc) in the newborn rat or the ia infusion of spantide (1, 2 mumol/kg) significantly inhibited the the stimulation-induced increase of the blood flow. These results suggest that substance P released from the peripheral endings of sensory nerve may be involved in vasodilation following electric stimulation of the sciatic nerve in rat.

Analgesics↗
PubMed1989

Solution synthesis of human neuropeptide Y (hNPY).

Human neuropeptide Y (hNPY) was synthesized in a conventional manner by assembling seven peptide fragments followed by reduction of the Met(O) residue with phenylthiotrimethylsilane and subsequent deprotection with 1 M trimethylsilyl trifluoromethanesulfonate (TMSOTf)-thioanisole in trifluoroacetic acid (TFA). Alternatively, deprotection was performed in a two-step manner; first, treatment with 1 M trimethylsilyl bromide-thioanisole in TFA, and then with 1 M TMSOTf-thioanisole in TFA. After purification by gel-filtration on Sephadex G-25, followed by reversed-phase high-performance liquid chromatography, a highly purified sample of synthetic hNPY was obtained in both cases. When administered in dogs, synthetic hNPY was as active as porcine NPY in terms of the effects on systemic arterial blood pressure, pancreatic blood flow, and superior mesentric artery (SMA) blood flow. Met(O)17-hNPY was found to be as active as the parent sample in these bioassays.

Amino Acid Sequence↗
PubMed1987

Synthesis of porcine neuropeptide Y(NPY) in solution.

The porcine neuropeptide Y (NPY), a 36-residue peptide amide, was synthesized by assembling six peptide fragments followed by thioanisole-mediated deprotection with trifluoromethanesulfonic acid in trifluoroacetic acid. beta-Cycloheptyl aspartate, Asp(OChp), was employed to suppress base-catalyzed succinimide formation. When administered to dogs, the purified peptide (10 micrograms/kg) caused prolonged increase of systemic arterial blood pressure and decreased pancreatic blood flow.

Animals↗