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Biomedical subjects

Y Fukuba

Publications and source records attributed to Y Fukuba.

At least 37 records · Page 2Linked to original sources
PubMed1994

Statistical evidence consistent with two lactate turnpoints during ramp exercise.

A number of studies have identified the existence of two ventilation thresholds during ramp or incremental exercise to exhaustion on the cycle ergometer. This study was undertaken to investigate whether two threshold turnpoints could be identified in blood lactate concentration data collected at such times. Five trained athletes provided serial blood samples on several occasions each during a 3-month period of training. Blood lactate concentration was analysed by fitting models with no, one or two turnpoints. Ordinary residuals from the first two models were often found to exhibit an oscillatory behaviour consistent with the existence of two turnpoints in lactate concentration. A comparative analysis of goodness of fit of these models revealed that the model with two turnpoints was significantly better than either of the simpler models. This suggests that two transitions exist, which divide the time domain for blood lactate concentration in ramp exercise into three regions. These two transitions may correspond to the two ventilation thresholds.

Adult↗
PubMed1994

Functional analysis of thymic B cells.

The expression of low- and high-affinity interleukin-5 receptors (IL-5Rs) on thymic B cells and reactivity of thymic B cells to IL-5 was investigated. Thymic B cells consist of two populations (CD5+ and CD5- B cells), as previously described. Three-color FACS analyses using anti-CD5, anti-IgK, and anti-IL-5R mAbs reveal that approximately 60% of both populations (CD5+ and CD5-) in the thymus possess IL-5R, detected by mAb H-7. In Scatchard plot analyses, IL-5Rs on thymic B cells are observed as low affinity receptors; the high-affinity IL-5R, which is known to be expressed on some IL-5-activated splenic B blasts or some IL-5-dependent cell line cells, is not clearly detected on thymic B cells. The reactivity of thymic B cells to IL-5 is found to be significantly lower than that of splenic B cells both in proliferative responses and LPS-induced IgM and IgA antibody responses. These findings are compatible with the expression of the low-affinity IL-5R on thymic B cells. The responsiveness of thymic B cells to either IL-6 or the combination of IL-4, IL-5 and IL-6 is also lower than that of splenic B cells. Furthermore, the thymic B cells are found to induce neonatal tolerance. Therefore, thymic B cells act as antigen-presenting cells in the negative selection of thymocytes, rather than as antibody-producing cells under the influence of foreign antigens and/or regulatory cytokines.

Animals↗
PubMed1994

Reproducibility of VO2-VCO2 relationship during incremental exercise protocol.

We examined the effect of two different slope protocols to the reproducibility of the VO2-VCO2 relationship and the lactic acidosis threshold (LAT) during incremental exercise. Two adult male subjects performed a cycle ergometer exercise 2 to 4 times repeatedly in which the increase of work rate was 25 W every 1 or 2 min according to experimental design method. Gas exchange parameters during each exercise was measured every 10 s. The V-slope method was applied to the data which remained after the deletion of the data during the transient phase with the onset of exercise and above respiratory compensation of metabolic acidosis (RCMA), for detecting LAT and summarizing the VO2-VCO2 relationship below and above LAT. LAT had a high reproducibility whichever slope protocol was used. The confidential limit of LAT estimated by a statistical method was about +/- 0.1 l/min in terms of VO2. There were stable and reasonable responses of VO2-VCO2 during incremental exercise in which the work rate increased 25 W every 1 min.

Acidosis, Lactic↗
PubMed1994

[Effect of habitual physical activity on physical fitness and serum cholesterol in middle-aged male workers].

The effects of habitual physical activity on physical fitness parameters and serum cholesterol profile were studied in middle-aged male workers. The subjects were 3376 middle-aged men (age: 30-59 yrs) who worked at two enterprises in HIROSHIMA Prefecture. As for physical fitness parameters, grip strength, vertical jump, side step, and step test scores were measured. Atherogenic index was calculated as (total Chol-HDL Chol)/(HDL Chol). Because daily physical activity mainly consists of physical activities during leisure time and working time, by using a questionnaire, physical activity during leisure time was assessed and categorized by frequency into three categories: 'frequently', 'sometimes', and 'seldom': and physical activity during work was categorized as 'high' or 'low' according to the average walking time per day during work. The effect of these physical activities on physical fitness parameters and serum cholesterol profile was evaluated by analysis of covariance (PC-SAS: GLM procedure) adjusting for several confounding factors such as age, body mass index, type of job, smoking and drinking habits. The main results are summarized as follows: 1) Physical activity during leisure time was positively related to vertical jump, side step, and step test score, independent of physical activity during working time, and 2) physical activity during leisure time was negatively associated to LDL-C and AI in the group with 'low' physical activity during work. These results show that in middle-aged male workers, even moderate or light physical activity during leisure time has some beneficial health promoting effects through changes in physical fitness and serum cholesterol profile.

Adult↗
PubMed1993

O2 uptake kinetics above and below the lactic acidosis threshold during sinusoidal exercise.

O2 uptake (VO2) kinetics at the onset of a constant work rate exercise are difficult to describe for work rates above the lactic acidosis threshold (LAT), because the steady-state level of VO2 response can usually not be identified. To describe the ability of the O2 transport system to deliver and the cells to utilize O2 above the LAT relative to that below the LAT, we applied a fluctuating (sinusoidal) variation of work rate. After 4 min of constant work at the midpoint of the sinusoidal work rate, a fluctuating work rate, at a period of 4 min, was applied below the LAT for the next 16 min. This was repeated in a range of work rates above the LAT with the same sine-wave amplitude. VO2 response appeared to follow a sinusoidal pattern similar to that of work rate for below- and above-LAT exercise. However, the amplitude of the VO2 response was significantly reduced (5.4 +/- 2.6 vs. 7.6 +/- 1.9 ml.min-1 x W-1, P < 0.01), and the phase lag increased above- compared with below-LAT work rate. VO2/heart rate fluctuations were dramatically reduced, whereas heart rate amplitude decreased and phase lag increased, for above-LAT sinusoidal work rate changes. These results suggest that VO2 kinetics are slowed in the work rate domain above the LAT relative to that below the LAT and that VO2 kinetics could be limited by the O2 transport mechanisms to the exercising muscle.

Acidosis, Lactic↗
PubMed1993

[Cigarette smoking and physical fitness].

In this review, previous studies regarding the effects of cigarette smoking on parameters of physical fitness such as endurance performance, muscle strength, step test score, body mass index, blood pressure, serum lipoprotein profile, etc., have been summarized with a special reference to the quality of life for middle-aged and elder men, including the result of recent studies by the present authors. Additionally the hypothesized mechanisms of cigarette smoking to atherosclerosis have been shown. It is concluded mainly from our recent studies that: 1) the smoking has an effect to impair not only the aerobic power, but also the anaerobic power, 2) the abstention from chronic smoking would be expected to improve the parameters of physical fitness, and 3) even though the duration from the onset of smoking is less than one year, i.e., a relatively short-term smoking habit, the smoking has a serious damage to the several parameters of physical fitness.

Aged↗
PubMed1992

Bone marrow transplantation as a strategy for treatment of non-insulin-dependent diabetes mellitus in KK-Ay mice.

The effects of allogeneic bone marrow transplantation (BMT) on non-insulin-dependent diabetes mellitus (NIDDM) were examined using KK-Ay mice. KK-Ay mice reconstituted with KK-Ay bone marrow cells showed glycosuria, hyperinsulinemia, and hyperlipidemia. However, KK-Ay mice (H-2b) that had been lethally irradiated (9.0 Gy) and then reconstituted with T cell-depleted bone marrow cells from normal BALB/c mice (H-2d) showed negative urine sugar with decreases in serum insulin and lipid levels 4 mo after BMT. Morphological recovery of islets and glomeruli was also noted after allogeneic BMT. These findings suggest that BMT can be used to treat not only a certain type of NIDDM but also its complications such as hyperlipidemia and diabetic nephropathy.

Animals↗
PubMed1992

Origin of thymic and peritoneal Ly-1 B cells.

Murine Ly-1 B cells were first found in the peritoneal cavity (Per C). It has been thought that Ly-1 B cells are responsible for the development of autoimmune diseases, since they spontaneously produce autoantibodies. However, we have found that such Ly-1 B cells are present in the thymus of normal mice, and that they play a crucial role in negative selection in the Mls system. In addition, thymic Ly-1 B cells and Per C Ly-1 B cells have been found to differ in function, ontogeny and location. In this communication, we report on the different origins of these cells. C57BL/6 mice are lethally irradiated and reconstituted with fetal (day 14) liver cells or bone marrow cells from 4-, 6- or 12-week-old mice. Fetal liver cells are shown to have the capacity to reconstitute both thymic and Per CLy-1 B cells, whereas bone marrow cells from 6- or 12-week-old mice have the capacity to reconstitute thymic Ly-1 B cells, but not Per C Ly-1 B cells, indicating that fetal hemopoietic stem cells (HSC) differ from HSC in the bone marrow of adult mice, and that thymic and Per C Ly-1B cells have different origins.

Age Factors↗
PubMed1992

Ventilatory dynamics in children and adults during sinusoidal exercise.

The ventilatory response to sinusoidally varying exercise was studied in five adults and seven prepubertal children to determine whether the faster kinetics of ventilation observed in children during abrupt changes in exercise intensity remained more rapid when exercise intensity varied continuously. Each subject exercised on a cycle ergometer first against a constant load and then against a load fluctuating over six different periods ranging from 0.75 to 10 min. The pedal rate was kept constant for all loads. The inspiratory minute ventilation was determined breath-by-breath. Amplitude (A) and phase angle (phi) of the fundamental component and the first harmonics of the ventilatory response were calculated by Fourier analysis for an integer number of waves for each period. From the relationship between A, phi and frequency, dynamic parameters of a first order model with and without delay were compared between adults and children. Firstly we found that the ventilatory time constant was significantly faster in children: 49.7 (SD 9.1) s vs 74.6 (SD 11.1) s (P less than 0.01). Secondly, the change in A and phi with the frequency was not however characteristic of a first order system without delay in most of the subjects (phi greater than 90 degrees for the shorter periods). Thirdly, even when the ventilatory control system was described as a first order model with a positive delay, time constants remained significantly shorter in children: 45.6 (SD 5.7) s vs 67.4 (SD 13) s (P less than 0.01). The ability to increase ventilation faster in children appeared to be a characteristic of the ventilatory control system during exercise independent of the type of drive used.

Adolescent↗
PubMed1992

Effects of K-76COOH (MX-1) on immune response: induction of suppressor T-cells by MX-1.

K-76COOH (MX-1), isolated from the cultured supernatant of a species of fungi imperfecti, Stachybotrys complement nov. sp. K-76, is an inhibitor of the complement component, C5. The effects of MX-1 on various immune responses were investigated. MX-1 enhanced the response of spleen cells to PHA and LPS: MX-1 at 0.01-250 micrograms/ml for PHA and at 10-250 micrograms/ml for LPS. In contrast, it inhibited the response to Con A: MX-1 at 0.01-500 micrograms/ml for spleen cells and at 100-500 micrograms/ml for thymocytes. MX-1 and IL-1 synergistically acted to enhance the Con A response of spleen and thymus cells from which accessory cells and Ia-positive cells had been removed by passing through Sephadex G-10 columns and treating with anti-Ia monoclonal antibody plus complement. T-cells pretreated with MX-1, IL-1 and Con A for 3 days suppressed not only the response of B-cells to LPS but also the production of anti-SRBC antibodies. In addition, MX-1 was found to increase CD8+ T-cells. These results suggest that MX-1 acts on T-cells to induce suppressor T-cells.

Animals↗
PubMed1992

The clearance rate of exercise-elevated blood lactate following physical training.

In this paper, previous studies regarding the effect of physical training on the disappearance rate of blood La during recovery after strenuous exercise have been briefly summarized. The results of our own recent study of this problem have also been added. It may be concluded that there is some evidence for an improved lactate metabolic clearance rate resulting from physical training in human subjects, when the degradation rate is estimated from serial blood samples taken during a standard ramp ergometer test to exhaustion during each week of a training/detraining sequence. This beneficial effect of training, however, may also be influenced by the initial physical status of the subject and the nature of the training program.

Exercise↗
PubMed1992

[Control of breathing during exercise].

Although the control of breathing during exercise has been studied extensively that both neural and humoral factors may play a role in mediating the exercise hyperpnea, it remains unresolved whether the response is due solely to neural or humoral mechanisms and how the pulmonary gas exchange matches to the tissue exchange rates. At just onset of exercise ventilation can increase abruptly within 1 to 2 breathes (Phase I). Such a rapid increment of ventilation is not attributed to the humoral factor(s) due to the circulation delay from muscle metabolites. More rapid mechanism(s) such as irradiation from brain stream, afferent neurogenic control, blood flow increment as cardiodynamic theory might be considered. During moderate exercise intensity with a step function, ventilation increased exponentially to the steady state (phase II) after an abrupt increase at just onset of exercise. In this phase II, the breathing is controlled as to exchange the oxygen and carbon dioxide at rates appropriate for the acid-base homeostasis regulation. As a result, arterial blood gases and acid-base status must maintain within a narrow range despite of extremely enlarged metabolic rates by exercise. Some humoral factor(s) might be mediated for the control of breathing such as mean steady state error theory, arterial blood gases oscillation theory, feedback system by CO2, or optimization theory. At the heavy exercise intensity, anaerobic metabolism was supplemented to product for the enhanced energy requirement, so that ventilation increased non-linearly with oxygen uptake due to the lactoacidosis and its buffering activity. There has been a debate concerning cause and effect relationship between blood lactate increment and hyperpnea during exercise. Recently, arterial potassium concentration resulted from depolarization due to muscle contraction during exercise might stimulate to carotid bodies for increasing ventilation.

Animals↗
PubMed1992

Effects of anticipation, prior-exercise, and breathing frequency to ventilatory response during step exercise: a preliminary study.

We examined the effects of anticipation, prior-exercise, and restricted breathing frequency on the ventilatory transient response to bicycle step exercise (75 W, 4 min, 50 rpm), i.e., 1) whether the increase of work rate was anticipated by the subject or not, 2) whether the exercise was preceded by light exercise (25 W), or rest, and 3) whether the exercise entrained the breathing frequency (f: 12.5/min, or 25/min) or not (voluntary). The corresponding step-on exercise was randomly performed at least two to five times by one adult male subject. As a result, a) the initial rapid ventilatory component, phase 1, was not observed when initiated from light exercise, whereas the overshot phase 1 was observed from rest in anticipation and voluntary breathing frequency condition due to the rapid increase of tidal volume; b) compared with the anticipation condition, the phase 1 response of VE in the non-anticipation condition was slower with prior-rest, and not with prior-light exercise; and c) the restriction of the breathing frequency for entraining the exercise rhythm did not affect the initial rapid response, but decreased the fluctuation of VE in the steady state, compared to the condition of voluntary breathing frequency.

Adult↗
PubMed1990

Non-invasive automatic determination of anaerobic threshold using double gas exchange parameters.

A new technique for determining the anaerobic threshold (AT) in real-time during a progressive exercise test was proposed with special consideration to its safety. We applied the discriminant analysis based on the linear logistic regression model to two groups of gas exchange parameters at times just before and after the lactate (LA) threshold (determined by blood LA kinetics; the external criterion of AT) during the incremental exercise test in 21 young males. As a result, the selected variables for estimating AT accurately (the discriminant rate = 100%), were VE/VO2 and the relative change in VE. Our idea of the new technique for determining AT is based on the probability function (p(x)) derived from the discriminant analysis. At each time at which the gas exchange parameters are acquired during the exercise test, p(x) is calculated, and the decision whether the present exercise level is in the pre, just, or post-AT level is made by the p(x). The technique is able to stop the exercise test as quickly as possible after passing through the AT level. To evaluate the new technique, the data set of 66 females (aged 16-57) was applied as a form of simulation. It was shown that the exercise test could be stopped by the technique at a level of only 0.2-0.5 l/min in VO2 higher than AT. This advantage of the technique makes the exercise test safer for middle-aged or old men, and patients during cardiac rehabilitation.

Adolescent↗
PubMed1990

Application of modeling to lactate kinetics in exercise.

The recent modeling technique to lactate (La) kinetics in exercise, and its availability, application, and limitation were summarized. Two examples were come up for discussion. One is the application of the compartment model (i.e., the description by the linear differential equations) to systemic La kinetics in exercise, and the other is the current controversy on anaerobic threshold, that is, the reexamination of the several proposed models of blood La kinetics during ramp exercise. In conclusion, considering the various limitations in current in vivo experimental approach on man, the theoretical approach with mathematical modeling, as one of the major strategies, gives full play to clarify the La metabolism in exercise.

Computer Simulation↗
PubMed1989

New mathematical modelling of blood lactate kinetics during ramp mode exercise in man.

The lactate (LA) kinetics of the whole body in exercise was described using the two-compartment model in consideration of the underlying physiological mechanism, and LA kinetics during the ramp mode exercise was analyzed. The estimated pattern of the glycolytic energy supply showed the progressive increase concurrently with the onset of ramp mode exercise and this pattern was just like a ramp phenomenon. Based on this result, it is proposed that blood LA kinetics during ramp exercise should be described mathematically as a continuous model, called "2nd-order model."

Exercise↗
PubMed1988

Comparison of objective methods for determining ventilatory threshold.

This study was undertaken to compare and re-examine the relation of lactate threshold (LT) and ventilatory threshold (VT), using six objective determination methods proposed previously. Twenty-one young male subjects performed a cycle exercise test in which the work rate was increased by 150 kg.m every 2 min up to his limit of volitional fatigue. Through each test, gas exchange parameter measurements were made every 1 min (every 30 s at nearly maximal level), and the venous blood samples were taken from a warmed ear lobe at each work rate for determining blood lactate concentration. LT and its variance were determined by the intersecting straight lines regression. LT ranged from 0.72 to 1.40 l/min in terms of VO2, and the mean value of S.D. for each LT was about 0.1 l/min. Each objective method for determining VT used in this study was based on the simple modelling of the criterion for visual detection of VT, that is the non-linear increase in VE or the systematic increase in VE/VO2. When the relationship between LT and VT was examined, VT by the objective methods based on determining minimum value of VE/VO2 showed relatively high consistency with LT. Of 16-20 individuals out of all 21 subjects, there were VT within LT +/- 0.2 in VO2. It is concluded that VE/VO2 is a more sensitive index for detecting VT than VE in the gas exchange parameters, and the objective VT determination method based on minimum value of VE/VO2 could facilitate estimation of LT within an error of +/- 0.2 l/min VO2 in most normal individuals.

Adult↗