Search PubMed⌕ Search

Biomedical subjects

K Aoki

Publications and source records attributed to K Aoki.

At least 325 records · Page 18Linked to original sources
PubMed1997

Circadian variation of sweating responses to passive heat stress.

The aim of present study was to examine whether sweating responses to passive heat stress change with the circadian rhythm of internal temperature. Six men had their legs immersed in water at 42 degrees C for 60 min in an ambient temperature of 28 degrees C on four separate days. Experiments were conducted at four different times [06.00 h (morning), 12.00 h (daytime), 18.00 h (evening) and 24.00 h (night)]. We measured oesophageal temperature (Toes), mean body temperature (Tb), local sweating rate (msw) on the forehead, back, forearm and thigh, the densities of activated sweat gland (ASG) on the back, forearm and thigh, and the frequency of sweat expulsion per minute (Fsw) which has been suggested to represent central sudomotor activity. Sweat gland output (SGO) on each site was calculated by dividing msw by ASG. ASG was significantly higher on the forearm than on the back and thigh, and SGO was significantly lower on the forearm than on the back and thigh. However, ASG and SGO did not significantly change over the day. Tb and Toes thresholds for the onset of sweating showed a significant change with both the temperature rhythms at rest prior to each procedure, while the slopes of the relationships Fsw-Tb and msw-Fsw showed no significant difference over the day. We suggest that the circadian variation of sweating response to passive heat stress is regulated by a central sudomotor mechanism rather than by sweat gland function.

Adult↗
PubMed1997

Cranial anomaly of homozygous rSey rat is associated with a defect in the migration pathway of midbrain crest cells.

Craniofacial development of vertebrates depends largely on neural crest contribution and each subdomain of the crest-derived ectomesenchyme follows its specific genetic control. The rat small eye (rSey) involves a mutation in the Pax-6 gene and the external feature of rSey homozygous embryos exhibits craniofacial defects in ocular and frontonasal regions. In order to identify the mechanism of craniofacial development, we examined the cranial morphology and migration of cephalic crest cells in rSey embryos. The chondrocranial defects of homozygous rSey embryos primarily consisted of spheno-orbital and ethmoidal anomalies. The former defects appeared to be brought about by the lack of the eye. In the ethmoid region, the nasal septum and the derivative of the medial nasal prominence were present, while the rest of the nasal capsule, as well as the nasal and lachrymal bones, were totally absent except for a pair of cartilaginous rods in place of the nasal capsule. This suggests that the primary cranial defect is restricted to the lateral nasal prominence derivatives. Dil labeling revealed the abnormal migration of crest cells specifically from the anterior midbrain to the lateral nasal prominence in homozygous rSey embryos. Pax-6 was not expressed in the crest cells but was strongly expressed in the frontonasal ectoderm. To determine whether or not this migratory defect actually resides in environmental cues, normal midbrain crest cells from wild-type embryos were labeled with Dil and were orthotopically injected into host rSey embryos. Migration of the donor crest cells into the lateral nasal prominence was abnormal in homozygous host embryos, while they migrated normally in wild-type or heterozygous embryos. Therefore, the cranial defects in rSey homozygous embryos are due to inappropriate substrate for crest cell migration towards the lateral nasal prominence, which consistently explains the cranial morphology of homozygous rSey embryos.

Animals↗
PubMed1997

Modulation of GABAC response by Ca2+ and other divalent cations in horizontal cells of the catfish retina.

GABAC responses were recorded in cultured cone-driven horizontal cells from the catfish retina using the patch clamp technique. At a holding potential of -49 mV, a bicuculline-resistant inward current (IGABA) was observed when 10 microM GABA was applied. The amplitude of IGABA increased as the extracellular Ca2+ ([Ca2+]o) was increased. Concentration-response curves of IGABA at 2.5 and 10 mM -Ca2+-o had similar EC50 (3.0 and 3.1 microM) and Hill coefficients (1.54 and 1. 24). However, the maximal response estimated at 10 mM [Ca2+]o was larger than the maximal response at 2.5 mM [Ca2+]o. Increasing Ca influx through voltage-gated Ca channels and the resulting rise in the intracellular Ca2+ concentration had no effects on IGABA. However, IGABA was inhibited by extracellular divalent cations, with the following order of the inhibitory potency: Zn2+ > Ni2+ > Cd2+ > Co2+. The inhibitory action of Zn2+ on the [Ca2+]o-dependent IGABA increase was noncompetitive. The action of [Ca2+]o on IGABA was mimicked by Ba2+ or Sr2+. These results demonstrate that the extracellular domain of GABAC receptors has two functionally distinct binding sites represented by Ca2+ (facilitation) and Zn2+ (inhibition). Since [Ca2+]o and [Zn2+]o change into the opposite direction by light, it seems likely that they modify cooperatively the efficacy of the positive feedback consisting of the GABAC receptor.

Animals↗
PubMed1997

Low serum M-CSF levels are associated with unexplained recurrent abortion.

PROBLEM: The purpose of this study was to determine whether the serum macrophage-colony stimulating factor (M-CSF) level is associated with early pregnancy loss in unexplained recurrent spontaneous abortion (RSA) patients. METHOD: We therefore compared preconceptional serum M-CSF levels between unexplained RSA patients and controls. The former comprised 44 bed-rest therapy patients and 43 intradermal immunization (IDI) patients receiving paternal lymphocyte therapy, who had experienced two and three or more consecutive first-trimester pregnancy losses, respectively. The controls were 46 healthy non-pregnant women. We also prospectively studied the association between M-CSF levels during pregnancy and adverse pregnancy outcomes. Sera from a total of 31 pregnant women, including 16 of the bed-rest therapy group and 15 of the IDI therapy group, were collected at the 4th, 6th, and 8th gestational weeks and were measured for M-CSF levels, using the enzyme-linked immunoadsorbent assay (ELISA) method established by Hanamura et al. RESULTS: Serum M-CSF levels were significantly lower in the non-pregnant RSA patients (460.0 +/- 185.6 U/ml; mean +/- SD) than in the control group (726.5 +/- 134.0 U/ml) and also were lower at the 8th, but not the 4th or 6th gestational week in those patients of both the bed-rest and IDI therapy groups whose outcome was pregnancy failure. CONCLUSION: Thus a low level of serum M-CSF was found to be associated with unexplained recurrent pregnancy loss in both the preconceptional and conceptional phases. These results raise the possibility that M-CSF may play an important role in the maintenance of pregnancy and that it can be used as a parameter for determining individuals at risk.

Abortion, Habitual↗
PubMed1997

Developmental pattern of 3-oxo-delta 4 bile acids in neonatal bile acid metabolism.

AIMS: To investigate whether a fetal pathway of bile acid synthesis persists in neonates and infants. METHODS: 3-oxo-delta 4 bile acids were determined qualitatively and quantitatively in the urine, meconium, and faeces of healthy neonates and infants, using gas chromatography-mass spectrometry. RESULTS: The mean percentage of 3-oxo-delta 4 bile acids in total bile acids in urine at birth was significantly higher than that at 3 or 7 days, and at 1 or 3 months of age. The concentration of this component in meconium was significantly higher than that in faeces at 7 days and at 1 or 3 months of age. CONCLUSIONS: The presence of large amounts of urinary 3-oxo-delta 4 bile acids may indicate immaturity in the activity of hepatic 3-oxo-delta 4-steroid 5 beta-reductase in the first week of postnatal life. Large amounts of this component in meconium may be due to the ingestion of amniotic fluid by the fetus during pregnancy.

Bile Acids and Salts↗
PubMed1997

Long-term probucol treatment reverses the severity of myocardial injury in watanabe heritable hyperlipidemic rabbits.

We previously reported that administration of NO donors ameliorates the severity of myocardial injury in cholesterol-fed rabbits. We now evaluated the effects of probucol, a lipid-lowering antioxidant that can preserve endothelium-dependent relaxation (EDR), in the aortas of cholesterol-fed rabbits. We examined the effects of short-term (7 days) or long-term (24 weeks) administration of 1% probucol on the size of infarcts resulting from 30 minutes of coronary occlusion followed by reperfusion (for 48 hours) in Watanabe heritable hyperlipidemic (WHHL) rabbits. Infarcts in untreated WHHL rabbits were significantly larger than those in the rabbits receiving the long-term but not the short-term treatment with probucol (72.2 +/- 5.4%, 37.6 +/- 6.4%, and 66.7 +/- 3.5%, respectively). Long-term probucol treatment also significantly reduced myeloperoxidase activity in both ischemic and nonischemic myocardium and suppressed P-selectin expression in the coronary vasculature. No significant differences were observed in hemodynamic parameters during myocardial ischemia/reperfusion. Long-term probucol treatment significantly reduced the surface area of atherosclerotic plaque lesions in the aorta (24.4 +/- 3.8% vs 46.3 +/- 6.3, P < .05). Moreover, long-term probucol treatment restored acetylcholine-induced EDR in aortic rings but did not affect sodium nitroprusside-induced relaxation. Finally, long-term probucol treatment resulted in significantly elevated cGMP levels in the aorta. These results indicate that long-term probucol treatment significantly ameliorates myocardial injury in heritable atherosclerotic rabbits, perhaps by reducing the accumulation of leukocytes in the myocardium and atherosclerotic vascular lesions. Thus, long-term administration appears to suppress the progression of atherosclerotic vascular disease in this animal model.

Administration, Oral↗
PubMed1997

Treatment of developmental dislocation of the hip in children after walking age. Indications from two-directional arthrography.

We treated 120 children between the ages of 12 and 31 months with 137 developmental dislocations of the hip and reviewed them at a mean follow-up of 14 years. We had used two-directional arthrography of all hips before reduction to evaluate the anterior, superior, and posterior portions of the limbus. Of the 137 hips, 64 had no interposed limbus in the AP view of the arthrogram, but 45 of these had an interposed anterior or posterior portion of the limbus. The hips with good stability and no interposed limbus in either AP or lateral arthrograms had excellent results by closed methods; in the other cases the results were less satisfactory. Our findings suggest that hips suitable for management by closed reduction can be identified by two-directional arthrography. Hips shown to have an interposed limbus are best managed by open reduction.

Age Distribution↗
PubMed1997

Assessment of insulin resistance in acromegaly associated with diabetes mellitus before and after transsphenoidal adenomectomy.

With a euglycemic hyperinsulinemic clamp method, whole-body insulin resistance was assessed in 6 cases with acromegaly associated with diabetes mellitus before and after transsphenoidal adenomectomy. The glucose infusion rate (GIR) correlated well with the plasma IGF-I level but poorly with that of GH. Further improvement in insulin sensitivity occurred 3-4 months after operation without substantial changes in plasma levels of both GH and IGF-I or glycemic control. These results indicate that GH excess can induce insulin resistance in association with plasma IGF-I and also through undefined secondary effect.

Acromegaly↗
PubMed1997

Changes in regional cortical temperature and cerebral blood flow after cortical spreading depression.

Regional cerebral blood flow (rCBF) measurement by laser Doppler flowmetry and cortical temperature measurement using thermoencephaloscopy (TES) were performed to investigate the relationship between the changes in rCBF and cortical temperature after induced cortical spreading depression (CSD) in rats. TES showed a gradually expanding thermoresponse like an extending circular wave after CSD induced by application of KCl. Similarly, a transient increase in rCBF spread from the site of stimulation with a velocity of propagation of 2.5 mm/min. Simultaneous monitoring of rCBF and cortical temperature showed that the transient increase in rCBF was associated with an initial decrease in cortical temperature, followed by an increase in cortical temperature. We suggest that the cortical temperature is regulated mainly by neurogenic control of the pial microvascular blood supply that is precisely adjusted to the metabolic needs of the cerebral cortex. Non-injured cortex with the fine vascular architecture must be preserved during neurosurgery to allow heat transfer from deep areas of the cortex.

Animals↗
PubMed1997

Relationship between serum carotenoid levels and cancer death rates in the residents, living in a rural area of Hokkaido, Japan.

The relationship between serum carotenoid levels and cancer death in rural Japanese residents, aged more than 39 years, was examined epidemiologically. The follow-up subjects participated in the comprehensive health examinations, every August from 1986 to 1989, were 929 males and 1424 females, living in a rural area of Hokkaido, Japan. During 2-8 years to December 1994, the ninety-eight deaths were observed among the cohort; that is, deaths from all causes were 67 males and 31 females, and cancer deaths were 34 males and 10 females. Serum samples at fasting were collected at the entry of the cohort and serum levels of beta-carotene, alpha-carotene and lycopene were measured by the HPLC method. The relation between the mortality rates and serum carotenoid levels was estimated statistically using the Cox's proportional hazard model. The results were as follows; the hazard ratio with the overall on high serum beta-carotene levels to those of lower was 0.46 (95% C.I.: 0.27-0.78) for all causes and 0.33 (95% C.I.: 0.14-0.75) for cancer deaths. This result suggested that high levels of serum beta-carotene may play some roles on preventing cancer death.

Adult↗
PubMed1997

Evaluation of cutoff levels for screening of gastric cancer using serum pepsinogens and distributions of levels of serum pepsinogen I, II and of PG I/PG II ratios in a gastric cancer case-control study.

This study was carried out to determine the cutoff levels of serum pepsinogen (PG) I, II and their ratio of PG I/PG II for gastric cancer to establish a better screening system. Optimal cutoff levels for gastric cancer screening using serum pepsinogens were determined using Youden's index. The sensitivity, specificity and Youden's index for gastric cancer cases were calculated according to sex, age and the stage of gastric cancer, and the maximum Youden's index in each category was adopted as the cutoff level for gastric cancer screening using serum pepsinogens. The maximal Youden's index in all gastric cancer cases was 0.37, corresponding to a cutoff level of PG I < 40 (micrograms g/l) and PG I/PG II < 3.5. The sensitivity and specificity for gastric cancer cases of these cutoff levels were 0.50 and 0.87, respectively. In future, better criteria for gastric cancer screening have to be examined with the estimation of Youden's index in addition to other epidemiological methods such as ROC (receiver operating characteristic) curves and/or cost benefit analyses.

Adult↗
PubMed1997

Smoking habits, local brand cigarettes and lung cancer risk in Okinawa, Japan.

To disclose the association between smoking habits and lung cancer in Okinawa, Japan, we analyzed the data from a case-control study conducted from 1988 to 1991. The analysis, based on 333 cases and 666 age-, sex- and residence-matched population controls, provided the following major findings. (a) The odds ratios (ORs) for current smokers relative to nonsmokers were much greater for squamous cell carcinoma than for adenocarcinoma. The OR was 9.82 for squamous cell carcinoma and 2.18 for adenocarcinoma in males, 28.2 and 1.14, correspondingly, in females. (b) Males who quit smoking for 20 years or more demonstrated no elevated lung cancer risk. (c) Among male current smokers, the more the number of cigarettes smoked per day, the higher the lung cancer risk for both cell types, but particularly for squamous cell carcinoma. In contrast, deep smoke inhalation significantly increased the risk for adenocarcinoma in particular. (d) Okinawan brand cigarettes were more strongly associated with the risk, compared with other brand ones. This finding might partly explain the higher frequency of lung cancer in males with the relatively lower smoking rate in Okinawa.

Adenocarcinoma↗
PubMed1997

Stereo fluoroscopy-assisted percutaneous needle puncture of the vertebral body.

The purpose was to determine whether real-time three-dimensional imaging by stereo fluoroscope could alleviate the nuisance of moving the fluoroscope C-arm during needle biopsy of the spine. Fifteen lumbar vertebrae of four beagle dog cadavers were used in a simulation. We used a newly devised portable-type stereo fluoroscope, which alternatively exposes the X-ray from left and right X-ray tubes so that a surgeon can decode left and right images displayed alternately on a monitor by using polarizing glasses. A 2-mm-diameter Kirschner wire was inserted into the vertebral bodies by a posterolateral approach without moving the C-arm. An axial view of the roentgenogram of each vertebra found all 15 wires to be appropriately inserted. This would appear to be a time-saving feature.

Animals↗
PubMed1997

[The effect of hypothermia on CSD propagation in rats].

In the cortical zone surrounding an ischemic or traumatic focus, CSD is a transient phenomenon involving interstitial ions, blood flow and metabolism and is believed to be completely reversible. However, it may extend to secondary brain injuries because CSD releases excitatory amino acids into the extracellular space. In order to prevent secondary brain injuries, it may be effective to block repeated CSD. This study was designed to determine whether hypothermia can block CSD propagation and whether this study is a potentially useful means for preventing secondary brain injuries. Male wistar rats weighing 270 g on average were used for the experiments. The animals were divided into two groups: hypothermic rats (33.5-34 degrees C, rectal temp.) and normothermic rats (37-37.5 degrees C). The changes in rCBF (regional Cerebral Blood Flow) were monitored in order to observe CSD. LDF (Laser Doppler Flowmetry) was used to measure rCBF. The two LDF probes were placed on the parietal cortex (4 mm apart). To elicit CSD, a needle stab injury was made on the cortex or a piece of paper soaked with 10% KCl was applied on the cortex. The velocity of CSD propagation was more prolonged in the hypothermic rats than in the normothermic rats (p < 0.01). There were smaller numbers of repeated CSD in the hypothermic rats than in the normothermic rats. Histological examination of the cerebral cortex revealed shrinkage neurons more distinctly in the normothermic rats than in hypothermic rats. From these results, we can speculate that hypothermic may block CSD propagation and that hypothermic therapy has the potential to prevent secondary brain injuries.

Animals↗
PubMed1997

[Factors affecting exercise capacity after coronary bypass grafting].

In order to determine the contribution of cardiac reserve and the peripheral muscle to exercise capacity in patients after Coronary Artery Bypass Grafting (CABG), 19 patients (18 males, 1 female, mean age 63.3 +/- 7.1 years, mean numbers of grafting 2.5 +/- 0.8) performed exercise tests at 1 week, 3 weeks, and 3 months after CABG. Ventilatory gas was analyzed throughout the testing and anaerobic threshold (AT) and peak oxygen uptake (peak VO2) was determined. During exercise testing, the cardiac index (CI) was measured, and the change in CI during exercise, delta CI = (CI at peak exercise) (CI at rest), was calculated. O2 delivery was derived from the product of CO and the oxygen content of arterial blood at peak exercise. The sectional area of the thigh muscles at the level of 10 cm above the patella was measured using a computed tomography before each test. Average peak VO2 at 1 week after CABG was 867 +/- 171 ml/min and it increased to 1,214 +/- 246 ml/min at 6 months. Average AT did not change from 1 week to 3 weeks, however, it increased significantly from 665 +/- 122 ml/min at 3 weeks to 873 +/- 181 ml/min at 6 months. The muscle area of the thigh increased significantly from 170 +/- 24 cm2 at 3 weeks after CABG to 186 +/- 27 cm2 at 3 months. delta CI showed a tendency to increase from 6.6 +/- 1.2 l/min/m2 at 1 week after CABG to 7.3 +/- 1.3 l/min/m2 at 3 weeks, and also showed a tendency to increase from 3 weeks to 6 months. Peak VO2 and AT correlated to delta CI at 1 weeks and also it correlated significantly to both the muscle area of the thigh and delta CI at 3 weeks, 3 months, and 6 months after CABG. The delta value of peak VO2 from 1 week to 3 weeks showed a significant correlation to those of delta CI and O2 delivery. Moreover, the delta values of peak VO2 and AT from 3 weeks to 3 months showed a correlation to those of delta CI and O2 delivery. These results suggest that both cardiac reserve and peripheral factors contribute to the exercise capacity up to 3 months after CABG, and, in particular, O2 delivery are important to increase exercise capacity.

Cardiac Output↗
PubMed1997

Effects of preconditioning with ebselen on glutathione metabolism and stress protein expression.

Selenium induces several proteins, including glutathione and stress proteins. These proteins have been shown to be cardioprotective against oxidative injury. To determine whether ebselen, a seleno-organic compound, can also induce these proteins and exert cardioprotective action, we examined the effects of preconditioning with ebselen on glutathione metabolism and stress protein expression and on myocyte injury induced by oxidative stress. Treatment of cultured cardiac myocytes with ebselen (0.3-30 microM) for 24 hr increased the reduced glutathione content. Glutathione reductase activity, but not glutathione peroxidase activity, was significantly elevated in a dose-dependent manner. Pretreatment with ebselen increased the expression of such stress proteins as heat shock protein 70 and heme oxygenase-1 (heat shock protein 32) in cardiac myocytes, as assessed by Western blotting. Expression of heat shock protein 70 was increased only at a higher dose of ebselen (30 microM), whereas expression of heme oxygenase-1 was markedly increased at a lower dose of ebselen (3 microM). Under these conditions, the myocyte injury induced by hydrogen peroxide or simulated ischemia/reperfusion, assessed by the release of lactate dehydrogenase into the culture medium, was reduced by ebselen pretreatment in a dose-dependent manner. Results indicated that cardiac myocytes pharmacologically preconditioned with ebselen for 24 hr exhibited resistance to oxidative injury, possibly via the up-regulation of glutathione metabolism and the expression of stress proteins.

Animals↗