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Biomedical subjects

T Fukunaga

Publications and source records attributed to T Fukunaga.

At least 127 records · Page 7Linked to original sources
PubMed1998

Effect of hypoxia on pulmonary blood flow-segmental vascular resistance relationship in perfused cat lungs.

To investigate the effect of alveolar hypoxia on the pulmonary blood flow-segmental vascular resistance relationship, we determined the longitudinal distribution of vascular resistance while increasing blood flow during hyperoxia or hypoxia in perfused cat lungs. We measured microvascular pressures by the micropipette servo-null method, partitioned the pulmonary vessels into three segments [i.e., arterial (from main pulmonary artery to 30- to 50-micron arterioles), venous (from 30- to 50-micron venules to left atrium), and microvascular (between arterioles and venules) segments] and calculated segmental vascular resistance. During hyperoxia, total resistance decreased with increased blood flow because of a reduction of microvascular resistance. In contrast, during hypoxia, not only microvascular resistance but also arterial resistance decreased with increase of blood flow while venous resistance remained unchanged. The reduction of arterial resistance was presumably caused by arterial distension induced by an elevated arterial pressure during hypoxia. We conclude that, during hypoxia, both microvessels and arteries >50 micron in diameter play a role in preventing further increases in total pulmonary vascular resistance with increased blood flow.

Animals↗
PubMed1998

Architectural and functional features of human triceps surae muscles during contraction.

Architectural properties of the triceps surae muscles were determined in vivo for six men. The ankle was positioned at 15 degrees dorsiflexion (-15 degrees) and 0, 15, and 30 degrees plantar flexion, with the knee set at 0, 45, and 90 degrees. At each position, longitudinal ultrasonic images of the medial (MG) and lateral (LG) gastrocnemius and soleus (Sol) muscles were obtained while the subject was relaxed (passive) and performed maximal isometric plantar flexion (active), from which fascicle lengths and angles with respect to the aponeuroses were determined. In the passive condition, fascicle lengths changed from 59, 65, and 43 mm (knee, 0 degrees; ankle, -15 degrees) to 32, 41, and 30 mm (knee, 90 degrees ankle, 30 degrees) for MG, LG, and Sol, respectively. Fascicle shortening by contraction was more pronounced at longer fascicle lengths. MG had greatest fascicle angles, ranging from 22 to 67 degrees, and was in a very disadvantageous condition when the knee was flexed at 90 degrees, irrespective of ankle positions. Different lengths and angles of fascicles, and their changes by contraction, might be related to differences in force-producing capabilities of the muscles and elastic characteristics of tendons and aponeuroses.

Adult↗
PubMed1998

Nonisometric behavior of fascicles during isometric contractions of a human muscle.

Fascicle length, pennation angle, and tendon elongation of the human tibialis anterior were measured in vivo by ultrasonography. Subjects (n = 9) were requested to develop isometric dorsiflexion torque gradually up to maximal at the ankle joint angle of 20 degrees plantarflexion from the anatomic position. Fascicle length shortened from 90 +/- 7 to 76 +/- 7 (SE) mm, pennation angle increased from 10 +/- 1 to 12 +/- 1 degrees, and tendon elongation increased up to 15 +/- 2 mm with graded force development up to maximum. The tendon stiffness increased with increasing tendon force from 10 N/mm at 0-20 N to 32 N/mm at 240-260 N. Young's modulus increased from 157 MPa at 0-20 N to 530 MPa at 240-260 N. It can be concluded that, in isometric contractions of a human muscle, mechanical work, some of which is absorbed by the tendinous tissue, is generated by the shortening of muscle fibers and that ultrasonography can be used to determine the stiffness and Young's modulus for human tendons.

Ankle Joint↗
PubMed1998

Pharyngeal cross-sectional area and pharyngeal compliance in normal males and females.

Obstructive sleep apnea syndrome is ascribed to pharyngeal dysfunction, but there are only a few reports about the normal morphological values in this anatomical region. We measured the pharyngeal cross-sectional area and the compliance (collapsibility), using the acoustic reflection technique with air breathing, in 181 healthy subjects (age 21-69 years). We assessed their sex-related differences, and the effects of age, body size and body postures on these parameters. The pharyngeal cross-sectional area, defined as the region from the fauces to the glottis, posturally changed with successive decreases in the sitting, left lateral decubitus and supine positions. The area was significantly greater in male than in female subjects in the sitting position (p < 0.01), but no difference was present in the recumbent positions. The pharyngeal cross-sectional area did not correlate with either age or body size. The specific pharyngeal compliance was greater in the males than in the females (p < 0.01) and increased with age only in the male subjects.

Adult↗
PubMed1998

Maturation site of dengue type 2 virus in cultured mosquito C6/36 cells and Vero cells.

The maturation of dengue virus (type 2, New Guinea B strain; abbreviated Den-2) in cultured mosquito C3/36 cells and Vero cells was studied by immunoelectron microscopy for the first 7 days after cells were infected, assays of the virus were done by the peroxidase-antiperoxidase method. Virus titers in both kinds of cells were highest on day 6. These cells were then observed with an electron microscope. Den-2 was round and measured about 50 nm in diameter. The virus matured mainly at the membranes of cytoplasmic vacuoles and vesicles, but a few budding viral particles were seen in the cell surface membrane. Immunogold labelling with rabbit antiserum against the E protein of Japanese encephalitis virus was used to locate specific antigens of the Den-2 envelope protein. The results showed that the E protein was in vacuoles, vesicles, and endoplasmic reticulum of the cells. In this study there were no differences between C6/36 cells and Vero cells infected with Den-2.

Animals↗
PubMed1998

Immunoradiometric assay for the N-terminal fragment of proatrial natriuretic peptide in human plasma.

Recently, the N-terminal fragment of proatrial natriuretic peptide (N-terminal proANP) has been proposed as a marker of chronic congestive heart failure. In this study, we established a two-step immunoradiometric assay using monoclonal antibodies and synthetic N-terminal proANP (1-67) as a standard. It allows us to measure plasma N-terminal proANP in only 4 h without prior extraction. The detection limit of this assay was 15 pmol/L for a 100 microL sample of plasma. Within-run CVs ranged from 1.7% to 2.9% and between-run CVs ranged from 4.2% to 5.1%. The dilution curves of plasma samples showed good linearity and analytical recovery was 89-104%. The mean (+/-SD) N-terminal proANP in plasma of 33 healthy subjects was 188 (+/-71) pmol/L and 1030 (+/-411) pmol/L in 25 patients with heart failure. Our immunoradiometric assay is rapid and precise enough for routine determination of N-terminal proANP in human plasma.

Antibodies, Monoclonal↗
PubMed1998

[Hepatic arterial infusion chemotherapy (HAI) for advanced hepatocellular carcinoma inefficacious with transcatheter arterial embolization (TAE)].

For 6 patients with advanced hepatocellular carcinoma (HCC) in whom TAE was inefficacious, we tried hepatic arterial infusion chemotherapy. 5-FU 500 mg/day + CDDP 10 mg/day was administered during 5 days. The AFP level was decreased for 4 patients, and 2 patients showed a partial response in CT image. These 2 patients have been alive over 22 and 18 months, respectively. These results suggest that 5-FU + CDDP HAI might be a useful treatment of HCC inefficacious with TAE.

Aged↗
PubMed1998

Evaluation of esophageal cancers using fluorine-18-fluorodeoxyglucose PET.

UNLABELLED: To evaluate glucose metabolism in esophageal cancer, 48 patients were studied using PET with 18F-2-fluoro-2-deoxy-D-glucose (FDG). METHODS: After transmission scans were obtained, 18F-FDG (148 MBq) was administered intravenously. In 11 patients, a dynamic study was performed to evaluate glucose metabolism. Using the changes of radioactivity in both plasma and tumor, rate constants (k1-k4) defined in the metabolic model for 18F-FDG were calculated. In 48 patients, static PET scans of the tumor (5-min scans) were obtained 60 min after administration. Fluorine-18-FDG activity within each tumor was corrected for physical decay and normalized by dose administration and patient weight to produce a standardized uptake value (SUV). RESULTS: Both the k3 value (n = 11) reflecting hexokinase activity and SUV (n = 13) were well correlated with hexokinase activity from the resected specimen (p < 0.05). Forty-seven of 48 patients before treatment revealed SUV greater than 2.0, but 10 normal control subjects and 1 esophageal benign tumor revealed less than 2.0 (accuracy rate 98.3%). Although clinicopathological findings did not correlate with SUV, except for two patients with carcinosarcoma, 23 patients with an SUV greater than 7.0 had a poor prognosis compared with 25 patients with SUVs less than 7.0. CONCLUSION: These findings suggest that 18F-FDG PET may be useful in distinguishing malignant tumors from benign lesions and in the preoperative evaluation of the prognostic factor.

Adult↗
PubMed1998

[Determination methods for human blood acetaldehyde].

Although a number of reports on human blood acetaldehyde have been published, most of them during alcohol intoxication are still various in each researcher. The difficult problems are summarized as follows; 1) low boiling point of acetaldehyde, 2) low level in blood, 3) rapid disappearance in blood, and 4) artefactual formation during the procedures. The most crucial problem is the artefactual formation from ethanol or other sources during the procedures. Hemolysation, heating and/or other analytical procedures cause the artefacts. In this report, several methods for the determination and the evaluation of the acetaldehyde levels are reviewed.

Acetaldehyde↗
PubMed1997

Mechanomyography of the human quadriceps muscle during incremental cycle ergometry.

The mechanical activity of the human quadriceps muscle during maximal incremental cycle ergometry was investigated by mechanomyography (MMG). MMG and surface electromyography (EMG) recordings of vastus lateralis muscle activity were obtained from nine males. Cycle ergometry was performed at 60 rev/ min and work load was incremented step wise by 20 W (3.2 Nm) every minute until volitional fatigue. The mean amplitudes of MMG (mMMG) and EMG (mEMG) during the contraction phase were calculated from the last six contractions in each load. The duration, load and work rate of exercise at exhaustion were 13.3 (1.6) min, 44.1 (5.5) Nm, 276.7 (34.7) W, respectively. A linear relationship between mMMG and load was evident in each subject (r = 0.868-0.995), while mEMG seemed to dissociate as the load became greater. In the grouped mean data, mMMG was linearly related to load whether aligned to the absolute (r = 0.995) or maximal (r = 0.995) load. Involvement of the noise component was further investigated by studying passive cycling by four subjects. Pedals were rotated passively for the first half of each stage (PAS) and the subject then pushed the pedals for the second half (ACT). In the lighter load region, the mMMG of ACT was as small as that of PAS. However, the change in the mMMG of PAS was very small compared with that of ACT. In conclusion, this study demonstrates a linear relationship between the mMMG of the quadriceps muscle and work load during maximal incremental cycle ergometry. The effect of movement noise was thought to be small and stable.

Adult↗
PubMed1997

Muscle architecture and function in humans.

The present study focused on architectural factors which are considered to influence the linkage of muscle fiber and joint actions. By means of real-time ultrasonography we can observe clearly and noninvasively in vivo the movement of fascicle and aponeurosis in human muscle and measure directly the changes in pennation angle and length of fascicle during muscle contraction. During dorsi and plantar flexion without load the movement of tendinous tissue in human tibialis anterior muscle (TA) appeared to synchronize with the displacement of the ankle joint, indicating that the muscle tendon complexes are stiff relative to the applied force, which is fairly small in the case of foot shaking motion. On the other hand, when the ankle joint was fixed and the TA contracted 'statically' the ultrasonic echo from deep aponeurosis in the TA was observed to move proximally, indicating the elastic component (i.e. mainly tendinous tissue) was stretched significantly by the contraction force of muscle. In the case of the kneejoint, a length of fascicle in vastus lateralis decreased by 18% with the extension of the knee passively from a 100 degrees flexed position. When the knee extensors contracted 'statically' the fascicle length decreased at every joint angles and its magnitude was greater (30%) when the knee was closer to full extension than (5%) at the flexed positions. The present results clearly show that the architecture of actively contracting muscle fibers differ considerably than that which occurs when movement is passively induced. The use of cadaver data in the study of architecture and modeling of muscle functions would result in inaccurate, and in some cases even erroneous results.

Animals↗
PubMed1997

Force-velocity relationships and fatiguability of strength and endurance-trained subjects.

The isokinetic forces, produced by a single as well as repetitive maximal knee extensions, and cross-sectional area (CSA) of the quadriceps femoris muscles were measured in 36 young adult males aged from 18 to 24 years: strength-trained (weight resistance-trained subjects, WT, N = 8), endurance-trained (middle distance runners, RUN, N = 13), and age-matched untrained subjects (UNT, N = 15). The CSA was measured using a B-mode ultrasound technique at the midpoint of the thigh length. The isokinetic forces at three velocities (1.05, 3.14 and 5.24 rad.s-1) were significantly correlated to CSA in all subjects (r = 0.01-0.849, p < 0.05). The absolute values in force development at three test velocities were significantly higher in WT than in RUN and UNT. While average values of force output per unit CSA were almost the same among the subject groups at test velocities of 3.14 and 5.24 rad.s-1, it was significantly higher in WT than in UNT at 1.05 rad.s-1. The repetitive maximal task consisted of 50 consecutive maximal knee extensions with constant velocity of 3.14 rad.s-1. The mean value of force (MF) of every 5 consecutive and all trials, respectively, was significantly correlated to CSA in all subjects (r = 0.448-0.885, p < 0.05). The average percentage of decline of MF with 50 maximal contractions was significantly lower in RUN (36 +/- 5%, mean +/- SE) than in WT (59 +/- 2%) and UNT (47 +/- 3%), and in UNT than in WT. The average values of MF per unit CSA for RUN became significantly higher than those for WT and UNT on and after the 36th-40th trial. Thus, force output during a single as well as repetitive maximal contractions was significantly correlated to muscle CSA. In terms of force per unit muscle CSA, however, WT and RUN showed specific force-velocity relation and fatiguability during repetitive maximal contractions, respectively, which could be considered as a result of muscle adaptation to their own training regimens.

Adaptation, Physiological↗
PubMed1997

Characteristics of body composition and muscle strength in college Sumo wrestlers.

The purpose of this study was to investigate the characteristics of body composition and force generation capacity in college Sumo wrestlers (N=13, age=19.8+/-0.3 yr, stature= 178.5+/-1.6 cm, body mass = 111.2+/-3.8 kg, X+/-SE) in comparison with untrained males (N=18, 20.3+/-0.2 yr, 170.1+/-1.7 cm, 59.2+/-1.4 kg). The Sumo wrestlers had significantly higher average values in relative fat mass (24.8+/-1.0%) and fat-free mass (83.3+/-2.0 kg), estimated by an underwater weighing method, than the untrained subjects (relative fat mass = 12.9+/-0.1 %, fat-free mass = 51.5+/-1.3 kg). Moreover, the Sumo wrestlers had 1.7 to 1.9 times greater cross-sectional areas (CSAs) of elbow flexors and extensors and knee extensors, determined by a B-mode ultrasound technique, compared to those of the untrained subjects. Force values produced during elbow flexion and extension and knee extensions tasks under isokinetic contraction mode at constant velocities of 1.05, 3.14 and 5.24 rad x s(-1) were significantly higher in the Sumo wrestlers than in the untrained subjects. The force value in all test conditions was significantly correlated to the related-muscle CSA, r=0.611-0.910 (p<0.05). The difference between the two groups in force per unit CSA (F x CSA[-1]) during elbow flexion was not significant at all test velocities. However, the Sumo wrestlers showed significantly lower F x CSA(-1) values in elbow extension at 5.24 rad x s(-1) and in knee extension at all test velocities. Thus, the body composition of the Sumo wrestlers was characterized by a high fat content and a large fat-free mass. Moreover, the Sumo wrestlers had considerably larger muscle CSAs of limbs than the untrained subjects. For the Sumo wrestlers, however, force output of the muscles with a pennate structure were not proportional to their CSAs, particularly in knee extensors.

Adipose Tissue↗
PubMed1997

Relationship between training frequency and subcutaneous and visceral fat in women.

We examined the interaction of two different frequencies of aerobic exercise training (30 min at 50-60% of maximal heart rate reserve per session) and a self-administered caloric restriction program on the changes in subcutaneous (SFM) and visceral (VFM) fat mass over a period of 13 wk. Twenty-six sedentary young women (27.9% body fat) were randomized into three groups: nonexercising control (C, N = 8); 1-2 sessions/wk plus a 240 kcal caloric restriction (1-2SW, N = 9); and 3-4 sessions/wk without caloric restriction (3-4SW, N = 9). There was a equivalent decrease in the percentage of body fat and total fat mass in both exercise groups compared with that in C. Reduction in SFM was significant in 3-4SW, but not in 1-2SW or C. A negative correlation was observed between training frequency and changes in SFM (r = -0.65). In contrast, VFM decreased significantly and equivalently in both 1-2SW and 3-4SW, but there was no correlation between training frequency and changes in VFM (r = 0.20). It is suggested that the decrease in SFM, but not VFM, is proportional to the amount of aerobic exercise training. A change in VFM appears to be related to an deficit in caloric balance either by dietary restriction (decrease caloric intake) or by increased caloric expenditure.

Abdomen↗
PubMed1997

Determination of fascicle length and pennation in a contracting human muscle in vivo.

We have developed a technique to determine fascicle length in human vastus lateralis muscle in vivo by using ultrasonography. When the subjects had the knee fully extended passively from a position of 110 degree flexion (relaxed condition), the fascicle length decreased from 133 to 97 mm on average. During static contractions at 10% of maximal voluntary contraction strength (tensed condition), fascicle shortening was more pronounced (from 126 to 67 mm), especially when the knee was closer to full extension. Similarly, as the knee was extended, the angle of pennation (fascicle angle, defined as the angle between fascicles and aponeurosis) increased (relaxed, from 14 to 18 degrees; tensed, from 14 to 21 degrees), and a greater increase in the pennation angle was observed in the tensed than in the relaxed condition when the knee was close to extension (< 40 degrees). We conclude that there are differences in fascicle lengths and pennation angles when the muscle is in a relaxed and isometrically tensed conditions and that the differences are affected by joint angles, at least at the submaximal contraction level.

Adult↗
PubMed1997

Estimation of active force-length characteristics of human vastus lateralis muscle.

The length and angles of fascicles were determined for the vastus lateralis muscle (VL) using ultrasonography in 6 subjects performing ramp isometric knee extension. The subject increased torque from zero (relax) to maximum (MVC) with the knee positioned every 15 degrees, from 10 degrees to 100 degrees flexion (0 degrees = full extension). As the knee was positioned closer to extension, fascicle length was shorter [116 +/- 4.7 (mean +/- SEM) mm at 100 degrees vs. 88 +/- 4.1 mm at 10 degrees (relax)]. The fascicle length of the VL decreased with increasing torque at each knee position [116 +/- 4.7 (relax) to 92 +/- 4.3 mm (MVC) at 100 degrees]. On the other hand, fascicle angles increased with an increase in torque. These changes reflected the compliance of the muscle-tendon complex which increased as the knee reached a straight position. The estimated muscle force of the VL was maximal (2,052 +/- 125 N) for a fascicle length of 78 +/- 2.7 mm (i.e. optimum length) with the knee positioned at 70 degrees of flexion. The relationship between muscle force and fascicle length indicated that the VL uses the ascending (knee < 70 degrees), plateau (70 degrees), and descending regions (> 70 degrees) of the force-length curve.

Adult↗
PubMed1997

Hypoglycemic effect of the rhizomes of Smilax glabra in normal and diabetic mice.

The hypoglycemic effect of the rhizomes of Smilax glabra ROXBURGH (Liliaceae) was investigated in normal and KK-Ay mice, one of the animal models of non-insulin dependent diabetes mellitus (NIDDM) with hyperinsulinemia. The methanol extract of rhizomes of Smilax glabra ROXBURGH (SM, 100 mg/kg body weight) reduced the blood glucose of normal mice 4 h after intraperitoneal administration (p<0.05), and also significantly lowered the blood glucose of KK-Ay mice under similar conditions (p<0.001). However, SM did not affect the blood glucose in streptozotocin-induced diabetic mice, one of the animal models of insulin-dependent diabetes mellitus (IDDM) with hypoinsulinemia. SM also suppressed epinephrine-induced hyperglycemia in mice. SM-treated KK-Ay mice significantly decreased the blood glucose in an insulin tolerance test. We concluded that the hypoglycemic effect of SM raised insulin sensitivity.

Animals↗