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Biomedical subjects

Y Yoneyama

Publications and source records attributed to Y Yoneyama.

At least 19 recordsLinked to original sources
PubMed1996

The relationship between uterine artery Doppler velocimetry and umbilical venous adenosine levels in pregnancies complicated by preeclampsia.

OBJECTIVE: The aim of this study was to evaluate the relationship between uteroplacental circulatory insufficiency and the fetoplacental release of adenosine in pregnancies complicated by preeclampsia. STUDY DESIGN: We performed uterine artery Doppler velocimetry and calculated the pulsatility index of the uterine artery, to detect uteroplacental circulatory insufficiency, immediately before cordocentesis in 39 pregnant women complicated by preeclampsia. Umbilical venous blood obtained by cordocentesis was then analyzed for blood gases, pH, and plasma adenosine levels. Increased plasma adenosine was taken to signal its increased release from the placenta and fetus relative to its rate of disappearance. RESULTS: The mean umbilical venous plasma adenosine level in the abnormal pulsatility index group was 1.78 +/- 0.17 mumol/L (mean +/- SEM, n = 25), significantly higher than in the normal pulsatility index group 0.58 +/- 0.14 mumol/L (n = 14, p < 0.001). Furthermore, in the abnormal pulsatility index group the elevation of plasma adenosine levels in the umbilical vein was found even in normoxic fetuses. CONCLUSION: Fetal plasma adenosine increases before uteroplacental circulatory insufficiency becomes severe enough to cause generalized fetal hypoxemia. We postulate that enhanced adenosine formation in the fetus, umbilical cord vessels, and particularly the placenta may, at least in part, contribute to control and maintenance of placental blood flow.

Adenosine↗
PubMed1995

Studies of the oxidation states of hemoglobin M Boston and hemoglobin M Saskatoon in blood by EPR spectroscopy.

The extent of the oxidation of Hemoglobin (Hb) M Saskatoon (beta 63His-->Tyr) and Hb M Boston (alpha 58His-->Tyr) in the patient's blood was determined by measurement of the intensity of EPR signals at g perpendicular = 6.0 for the normal subunits, g1 = 6.7 for the mutant subunits of Hb M Saskatoon and g1 = 6.3 for those of Hb M Boston, respectively. The amounts of reduced mutant subunits were estimated from the EPR signal intensities and the amounts of Hb present as mutant Hb in the blood. About 50% and 76% of mutant subunits in Hb M Boston and Hb M Saskatoon remained reduced in the fresh blood. Gentle shaking of the blood at 37 degrees C for 15 hours in air brought about autoxidation of the normal subunits as well as the mutant subunits of the two Hbs M, indicating that the presence of the mutant subunits facilitated autoxidation of the normal subunits. Possible involvement of NADH-metHb reductase in erythrocytes in maintenance of the reduced mutant subunits of Hb M Saskatoon was discussed.

Electron Spin Resonance Spectroscopy↗
PubMed1995

Role of prostaglandin I2 and prostaglandin E2 in the initiation of nonshivering thermogenesis during the simulation of birth in utero.

Because maximal nonshivering thermogenesis can commence only after occlusion of the umbilical cord, circulating stimulators and inhibitors were hypothesized to alter brown fat activity in the perinatal period. The roles of prostaglandin I2 (PGI2) and PGE2 in the initiation of nonshivering thermogenesis at birth were investigated. Indomethacin (45 mg bolus, 3 mg h-1 thereafter) was infused into 10 near-term fetal sheep to decrease prostanoid synthesis; 6 age-matched fetuses were infused with saline as controls. Sixteen hours later, birth was simulated in utero by sequentially cooling the fetus, ventilating its lungs with oxygen and occluding the umbilical cord. In the control fetuses, the plasma concentrations of PGI2 and PGE2 and free fatty acids, an index of nonshivering thermogenesis, were unaffected by cooling. Ventilation caused the concentration of PGI2 to increase 108% (P < 0.001) and that of PGE2 to decrease 26% (P < 0.05), while fatty acid concentrations increased 100% (P < 0.05). After cord occlusion, PGI2 concentrations remained elevated whereas PGE2 concentrations decreased a further 46% (P < 0.01), and fatty acid concentrations increased a further 100% (P < 0.05). In the indomethacin-treated fetuses, PGI2 and PGE2 concentrations decreased to 20% of the preinfusion values (P < 0.001) and did not change during the experiment. Cooling initiated a 300% increase in fatty acid concentrations (P < 0.05) and ventilation and cord occlusion induced no further significant changes. Thus, prostanoid concentrations follow changes in nonshivering thermogenic activity and support a regulatory role for PGI2 and PGE2 in the initiation of thermogenesis. Before birth, high concentrations of PGE2 favour suppression of thermogenesis, and after birth this inhibition is removed and there is stimulation by PGI2.

Animals↗
PubMed1994

Determination of the amounts and oxidation states of hemoglobins M Boston and M Saskatoon in single erythrocytes by infrared microspectroscopy.

The reduced abnormal subunits of two M-type hemoglobins, Boston (His alpha 58-->Tyr) and Saskatoon (His beta 63-->Tyr), have been determined in the presence of normal human hemoglobin A by measurement of C-O stretch bands in infrared spectra of carbon monoxide complexes. Use of an infrared microscope coupled to a Fourier transform infrared spectrometer of high sensitivity permitted measurements to be made on as small a hemoglobin mixture as is contained in a single erythrocyte. The abnormal subunits of both Hbs M exhibit bands near 1970 cm-1 compared with bands near 1951 cm-1 for the normal subunits. The increase in 1970 cm-1 band intensity upon erythrocyte reduction with dithionite provided a measure of the extent of abnormal subunit oxidation; in cell suspensions about 60% of the abnormal subunits of Hb M Boston and 80% for Hb M Saskatoon remained reduced. The amount of Hb present as abnormal Hb averaged about 25% for Hb M Boston cells and about 50% for Hb M Saskatoon cells. However, the ratio of Hb M to Hb A in individual cells varied markedly, with the ratio expected to decrease as the cell ages. These results demonstrate the unique utility of infrared microspectroscopy for the study of differences in abnormal Hb status among individual erythrocytes.

Carboxyhemoglobin↗
PubMed1994

Relationship between plasma adenosine concentration and breathing movements in growth-retarded fetuses.

OBJECTIVE: The purpose of this study was to investigate the relationship between plasma adenosine concentration and breathing movements in growth-retarded fetuses. STUDY DESIGN: We measured the incidence of fetal breathing movements and breathing rate immediately before cordocentesis in 26 growth-retarded fetuses at 31 to 38 weeks' gestation. Blood retrieved by cordocentesis was then analyzed for umbilical venous plasma adenosine concentration, blood gases, and pH. RESULTS: In growth-retarded fetuses with hypoxia and acidosis plasma adenosine concentration was elevated and the incidence of fetal breathing movements was reduced. The change in plasma adenosine concentration correlated inversely and significantly with the incidence of fetal breathing movements. CONCLUSION: Decreased breathing movements correlate with elevated plasma adenosine concentration in fetuses. We postulate that the enhanced adenosine formation in growth-retarded fetuses may modulate the inhibition of fetal breathing movements.

Adenosine↗
PubMed1994

Role of prostaglandin E2 and prostacyclin in nonshivering thermogenesis during simulated birth in utero.

Prostaglandin E2 (PGE2) inhibits and prostacyclin (PGI2), stimulates lipolysis in vitro. Their role in initiating nonshivering thermogenesis at birth was investigated in 16 fetal sheep at 129-143 days gestation. In 10 fetuses indomethacin, a prostaglandin synthesis inhibitor, was infused; in 6 fetuses saline was administered as a control. 16 h later birth was simulated in utero. The plasma levels of PGE2 and PGI2 were unaffected by cooling. In the control fetuses, ventilation with oxygen caused PGE2 to fall, PGI2 to rise, and initiated moderate thermogenesis, signaled by a twofold increase in plasma free fatty acids (FFA). After umbilical cord occlusion, PGE2 decreased further (PGI2 was unchanged) and thermogenesis accelerated. In indomethacin-treated fetuses, in which the prostanoids had decreased and remained at approximately 20% normal, cooling initiated moderate nonshivering thermogenesis, and ventilation and cord occlusion caused no further changes. Changes in plasma adenosine were similar in control and indomethacin-treated groups. We conclude that declining PGE2 and rising PGI2 contribute to the initiation of thermogenesis at birth, but that other agents possibly of placental origin may play a contributory role.

6-Ketoprostaglandin F1 alpha↗
PubMed1994

Plasma adenosine concentration in appropriate- and small-for-gestational-age fetuses.

OBJECTIVE: Our purpose in this study was to investigate the relationship between fetal plasma adenosine concentration and catecholamine concentration, blood gases, and pH in appropriate- and small-for-gestational-age fetuses. STUDY DESIGN: Cordocentesis was performed in 23 appropriate- and 14 small-for-gestational-age fetuses at 30 to 37 weeks' gestation for the measurement of umbilical venous blood plasma adenosine and catecholamine concentrations, blood gases, and pH. RESULTS: In small-for-gestational-age fetuses plasma adenosine concentration was higher, umbilical venous PO2 and pH were lower, and PCO2 was significantly higher than in appropriate-for-gestational-age fetuses. The elevation of plasma adenosine concentration was inversely related to umbilical venous PO2 and pH. CONCLUSION: Some small-for-gestational-age fetuses are exposed to diminished oxygen tension and acidotic blood gas values in utero. We postulate that the accompanying elevation of plasma adenosine may elicit protective adaptation during fetal asphyxia as a stress response.

Adenosine↗
PubMed1993

Disappearance of palmitic acid from plasma of fetal and newborn sheep.

These studies were undertaken to measure the kinetic constants that characterize the disappearance of a representative free fatty acid (FFA) from the plasma of fetal and newborn sheep. A bolus of albumin-complexed [14C]palmitic acid was infused intravenously, and during the next 8 min, 24 arterial samples were collected to characterize the disappearance curve. Palmitic acid disappearance from plasma was well described by a double-exponential model. When birth was simulated in utero, kinetic values were not changed by cooling. However, after intrauterine ventilation with O2, the volume of distribution of the FFA increased 29%, its plasma clearance rate decreased 26%, and its apparent half-life in the plasma lengthened from 0.8 to 1.2 min (all P < 0.01, n = 8). After umbilical cord occlusion, plasma clearance rate decreased a further 19% and half-life lengthened to 1.4 min. About 60% of the increase in FFA concentration during simulated birth is explained by increased release from adipose stores, and 40% is explained by decreased clearance. Further experiments tested the influence of FFA concentrations themselves. After infusion of unlabeled FFA, clearance of the tracer decreased 23% (P < 0.05, n = 5), a result consistent with a saturable membrane transporter of FFAs.

Animals↗
PubMed1992

Plasma adenosine and cardiovascular responses to dipyridamole in fetal sheep.

The effects of dipyridamole infusion on fetal arterial plasma adenosine level, [ADO], and the systemic cardiovascular system were studied in 10 fetal sheep at 130-135 days gestational age. Dipyridamole (0.25 mg/kg) was infused into the fetuses intravenously during normoxia and hypoxia. Plasma [ADO] was measured using high-performance liquid chromatography, (HPLC), and fetal heart rate and arterial blood pressure were monitored throughout the study. These studies were performed in the absence and presence of theophylline, an adenosine receptor antagonist. During normoxia (PO2, 23.8 +/- 2.0 Torr), dipyridamole infusion increased fetal plasma [ADO] from 0.82 +/- 0.10 microM to 1.41 +/- 0.16 microM within 1 min (P < 0.01) and fetal heart rate from 157 +/- 6 bpm to 174 +/- 7 bpm (P < 0.01), but did not change mean blood pressure. Fetal plasma [ADO] and fetal heart rate returned to basal levels quickly. Treatment with theophylline did not alter the elevation of plasma [ADO] after dipyridamole infusion, but abolished responses of fetal heart rate to dipyridamole infusion. After 15 min of hypoxia with an average arterial PO2 of 15.4 +/- 1.1 Torr, fetal plasma [ADO] increased to 1.15 +/- 0.14 microM (P < 0.01). Dipyridamole infusion then further raised fetal plasma [ADO] to 1.67 +/- 0.27 microM (P < 0.01). The duration of the increase of fetal plasma [ADO] after dipyridamole infusion was no longer in hypoxia than in normoxia, however there was no significant change in the pattern of transient fetal bradycardia and persistent hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1991

Unusual CO bonding geometry in abnormal subunits of hemoglobin M Boston and hemoglobin M Saskatoon.

To clarify the role of the proximal histidine (F8-His), distal His (E7-His), and E11 valine (E11-Val) in ligand binding of hemoglobin (Hb), we have investigated the resonance Raman (RR) spectra of the carbon monoxide adduct of Hbs M (COHb M) in which one of these residues was genetically replaced by another amino acid in either the alpha or beta subunit. In the fully reduced state, all Hbs M gave v3 at approximately 1472 cm-1 and vFe-His at 214-218 cm-1, indicating that they have a pentacoordinate heme and the heme iron is bound to either E7-His or F8-His. The porphyrin skeletal vibrations of the COHb M were essentially unaltered by replacements of E7- or F8-His with tyrosine (Tyr) and of E11-Val by glutamic acid (Glu). The vCO, vFe-CO, and delta Fe-C-O frequencies of COHb M Iwate (alpha F8-His----Tyr), COHb M Hyde Park (beta F8-His----Tyr), and COHb M Milwaukee (beta E11-Val----Glu) were nearly identical with those of COHb A. In contrast, the RR spectra of COHb M Boston (alpha E7-His----Tyr) and COHb M Saskatoon (beta E7-His----Tyr) gave two new Raman bands derived from the abnormal subunits, vFe-CO at 490 cm-1 and vCO at 1972 cm-1, in addition to those from the normal subunits at 505 cm-1 (vFe-CO) and 1952 cm-1 (vCO). The CO adduct of the abnormal subunits exhibited apparently no photodissociation upon illumination of CW laser with a stationary cell under which the normal subunit exhibited complete photodissociation.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1990

Mechanism of coloration of human lenses induced by near-ultraviolet-photo-oxidized 3-hydroxykynurenine.

Tha absorption spectra of human cataractous lenses, classified into four groups on the basis of coloration, were measured by a spectrophotometer equipped with an integrating sphere that is able to detect diffuse reflectance of solid materials. The results revealed that pale-yellow cataractous lenses showed a characteristic absorption spectrum with a peak near 365 nm, coincident with that of 3-hydroxykynurenine, and that brunescent cataractous lenses with high pigmentation showed an absorption spectrum with a peak over 400 nm, coincident with that of xanthommatin, a dimerized compound of 3-hydroxykynurenine. Depending on the coloration of the lens, the position of maximum absorption shifted from 365 to 410 nm and the optical density increased at visible regions. The changes in absorption spectra of pale-yellow lens homogenates were studied in the presence or absence of 3-hydroxykynurenine and by near-ultraviolet (UV) irradiation. Brown pigments were formed in the insoluble proteins of lens homogenates by 48 h of exposition of the samples with 3-hydroxykynurenine to UV irradiation. The absorption spectra of the brown pellets detected by an integrating sphere corresponded well to those of pellets which were obtained from the homogenates of intact human brunescent cataractous lenses. These results strongly suggest that 3-hydroxykynurenine and UV irradiation are involved in the brown pigmentation of human cataractous lenses by formation of xanthommatin.

Amino Acids↗
PubMed1990

Molecular pathology of hemoglobin M Saskatoon disease.

Absorption spectra of erythrocyte hemolysate from a normal subject, the Hemoglobin (Hb1) M Saskatoon patient and the Hb M Boston patients were investigated. Difference spectrum between the hemolysate from either freshly obtained or 37 degrees C-incubated blood of the Hb M Saskatoon patient and that of the normal blood suggested that about 50% of the abnormal chain were in the ferrous state in the patient's blood. In contrast, no abnormal chain containing the ferrous heme was detected in the hemolysate from the fresh blood of the Hb M Boston patient. Resonance Raman (RR) studies indicated that methemoglobin (metHb) M Saskatoon with a weak Fe-tyrosinate interaction contained the six-coordinate heme like normal metHb A whereas metHb M Boston had the five-coordinate heme. Studies on effects of pH on absorption and RR spectra of these three hemoglobins suggested that the coordinated tyrosinate in the abnormal chain of Hb M Saskatoon was dissociated at pH 5.0. This unique heme structure of Hb M Saskatoon may relate to the susceptibility for the reduction by erythrocyte methemoglobin reductases, which is responsible for mild cyanosis of Hb M Saskatoon disease.

Ferrous Compounds↗
PubMed1989

Characteristics in tyrosine coordinations of four hemoglobins M probed by resonance Raman spectroscopy.

Resonance Raman spectra of four hemoglobins (Hbs) M with tyrosinate ligand, that is, Hb M Saskatoon (beta distal His----Tyr), Hb M Hyde Park (beta proximal His----Tyr), Hb M Boston (alpha distal His----Tyr), and Hb M Iwate (alpha proximal His----Tyr), were investigated in order to elucidate structural origins for distinctly facile reducibility of the abnormal subunit of Hb M Saskatoon in comparison with other Hbs M. All of the Hbs M exhibited the fingerprint bands for the Fe-tyrosinate proteins around 1600, 1500, and 1270 cm-1. However, Hb M Saskatoon had the lowest Fe-tyrosinate stretching frequency and was the only one to display the Raman spectral pattern of a six-coordinate heme for the abnormal beta subunit; the others displayed the patterns of a five-coordinate heme. The absorption intensity of Hb M Saskatoon at 600 nm indicated a transition with a midpoint pH at 5.2, whereas that of Hb M Boston was independent of pH from 7.2 to 4.8. The fingerprint bands for the tyrosinate coordination as well as the Fe-tyrosinate stretching band disappeared for Hb M Saskatoon at pH 5.0, and the resultant Raman spectrum resembled that of metHb A, while those bands were clearly observed for Hb M Boston at pH 5.0 and for two Hbs M at pH 10.0. These observations suggest that the unusual characteristics of the heme in the abnormal beta chain of Hb M Saskatoon result from the weak Fe-tyrosinate bond, which allows weak coordination of the proximal histidine, giving rise to the six-coordinate high-spin state at pH 7.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemoglobin A↗
PubMed1989

[Development of a new system for measuring the mean film thickness of the white silicone on the fitness test of the denture base].

A new system is developed for measuring the mean film thickness of the white silicone on the fitness test of the denture base. This system is based on analysing the B/W film density replaced from the thickness of the silicone. The detective feature of this system is as follows: 1. An adequate correlation between the logarithm of the thickness of the white silicone and the logarithm of the B/W film density was estimated from the results of experimental values. 2. With use of the computer assembled into the system, it is capable to quickly process data. 3. Compared with the conventional method, the proper suggestion was gotten to the clinical data. 4. The system is available to use of investigating the bite force and the mean film thickness of the white silicone.

Bite Force↗
PubMed1989

[A case of acute spinal epidural hematoma with spontaneous resolution and its MRI].

A case of non-traumatic spinal epidural hematoma (SEH) with spontaneous resolution was reported. A 80-year-old woman was admitted to our hospital for her paraplegia of acute onset. She had had no specific previous history, and she did not either receive any drug or suffer from hypertension. On admission, general status was unremarkable. Flaccid paralysis of lower extremities and bilateral sensory disturbance of all modalities below the level of Th4 were observed. Deep tendon reflexes were normal in upper extremities, while absent in lower extremities. Babinski's sign was not elicited. From the findings of CT and metrizamide CT myelography, SEH of ventral type was presumed. MRI revealed hematoma compressing spinal cord over two vertebral segments, and widely spreading even to C7 rostrally and to Th10 caudally. Urgent surgical intervention was taken into consideration, but was not performed because of her rapid improvement: sensory disturbance alleviated from day to day, and she became able to walk within the 3rd day of hospitalization. Almost complete recovery from motor and sensory dysfunction was achieved in about 7 days after admission. Only 4 cases of spontaneous recovery of SEH have been reported so far, and this patient is the 5th such case. Although CT and metrizamide CT myelography are useful in diagnosing SEH, MRI is also proved to be an accurate and efficacious method for evaluation of its size, location and extent in the spinal canal.

Acute Disease↗
PubMed1988

Morphology and identification of Chrysops larvae from Nigeria.

Mature larvae of four Afrotropical species of Chrysops (Diptera: Tabanidae): C. centurionis Austen, C. distinctipennis Austen, C. longicornis Macquart and C. silaceus Austen, are described and illustrated from specimens collected in Nigeria, identified by rearing associated adult flies. The descriptions pay special attention to the value of ultrastructural characters, such as cuticular striations, observed by scanning electron microscopy (SEM).

Animals↗