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Biomedical subjects

T Fukunaga

Publications and source records attributed to T Fukunaga.

At least 91 records · Page 5Linked to original sources
PubMed2000

Fatigue responses of human triceps surae muscles during repetitive maximal isometric contractions.

Nine healthy men (22-45 yr) completed 100 repetitive maximal isometric contractions of the ankle plantar flexor muscles in two knee positions of full extension (K0) and flexion at 90 degrees (K90), positions that varied the contribution of the gastrocnemii. Electromyographic activity was recorded from the medial and lateral gastrocnemii and soleus muscles by using surface electrodes. Plantar flexion torque in K0 was greater and decreased more rapidly than in K90. The electromyographic amplitude decreased over time, and there were no significant differences between muscles and knee joint positions. The level of voluntary effort, assessed by a supramaximal electrical stimulation during every 10th contraction, decreased from 96 to 70% (P < 0.05) with no difference between K0 and K90. It was suggested that a decrease in plantar flexion torque was attributable to both central and peripheral fatigue and that greater fatigability in K0 than in K90 would result from a greater contribution and hence more pronounced fatigue of the gastrocnemius muscle. Further support for this possibility was provided from changes in twitch torque.

Adult↗
PubMed2000

Decrease in maximal voluntary contraction by tonic vibration applied to a single synergist muscle in humans.

The purpose of the study was to examine the effect of prolonged tonic vibration applied to a single synergist muscle on maximal voluntary contraction (MVC) and maximal rate of force development (dF/dt(max)). The knee extension MVC force and surface electromyogram (EMG) from the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM) during MVC were recorded before and after vibration of RF muscle at 30 Hz for 30 min. MVC, dF/dt(max), and the integrated EMG (iEMG) of RF decreased significantly after prolonged tonic vibration in spite of no changes in iEMG of VL and VM. The present results indicate that MVC and dF/dt(max) may be influenced by the attenuated Ia afferent functions of a single synergist muscle.

Adult↗
PubMed2000

Epithelial rests of Malassez express immunoreactivity of TrkA and its distribution is regulated by sensory nerve innervation.

The periodontal ligament is the connective tissue that fills the space between the tooth and its bony socket. It is abundantly innervated by the sensory and sympathetic nerves. We first investigated the immunoreactivity of TrkA, which is a high-affinity receptor of nerve growth factor (NGF), in the periodontal ligament of rats. Immunoreactivity was observed at the epithelial cells in the cervical and furcation regions of the molars. These epithelial cells, which gather together to form clusters or networks, are known as the epithelial rests of Malassez. Immunoreactivity was not observed in other non-neuronal cells, such as osteoblasts, fibroblasts, odontoblasts, cementoblasts, endothelial cells, and/or osteoclasts. On the basis of these findings, we investigated the possible involvement of sensory nerve innervation in the immunoreactivity of the epithelial cells. Denervation of the inferior alveolar nerve resulted in a marked decrease in the distribution area and size of the clusters of immunoreactive cells compared with those of sham-operated rats. These findings suggest that sensory nerve innervation may have a regulatory role in maintenance of the epithelial rests of Malassez expressing TrkA in the periodontal ligament.

Animals↗
PubMed2000

Implication of sphingolipid metabolism in the stability of the Golgi apparatus.

We examined the effects of short chain and long chain ceramides on the stability of the Golgi apparatus. Short chain ceramides, C(2)- and C(6)-ceramides, blocked brefeldin A-induced Golgi disassembly without affecting the rapid release of Golgi coat proteins, whereas they did not inhibit brefeldin A-induced tubulation of endosomes. Both short chain ceramides also retarded Golgi disassembly induced by nordihydroguaiaretic acid and nocodazole, suggesting that they stabilize the Golgi apparatus. In contrast to short chain ceramides, natural long chain ceramides, when incorporated into cells or formed within cells upon treatment with sphingomyelinase or metabolic inhibitors, enhanced brefeldin A-induced Golgi disassembly. These results suggest that sphingolipid metabolism is implicated in the stability of the Golgi apparatus.

Animals↗
PubMed2000

[Survey on postmortem examination to police surgeons and emergency physicians. Possibility of physicians' assist in mass-disaster].

We conducted a questionnaire survey of police surgeons and emergency physicians, inquiring about their experience of medicolegal investigation of death and their willingness to join a death investigation team in a major disaster. The questionnaire also asked about their knowledge about and interest in the forensic specialist system established by the Japanese Society of Legal Medicine. Police surgeons were generally willing to join an investigation team only if a disaster occurred in or close to their hometown, because they could not afford more than several days away from patient care. Although many of the emergency physicians were willing to join a death investigation team, they had difficulty in doing so without permission or orders from their employer or the authorities concerned. The survey found that the percentage of aged police surgeons was increasing among those surveyed. This fact, in combination with the current emphasis of postgraduate education on specialty training, threatens to cause a substantial lack of physicians available for medicolegal investigation of death. Therefore, it is urgently necessary to establish a system of training resident and emergency physicians in medicolegal investigation of death. In addition to providing postgraduate training in medicolegal investigation of death to prospective trainees who are emergency physicians at major hospitals in potential disaster-stricken areas, the medical school should incorporate forensic medicine in postgraduate training programs so that they can actively perform death investigation on disaster victims dying before or after arrival at their hospitals. Furthermore, the forensic community should make every effort to increase the number of autopsies in each department of forensic medicine and to expand the medical examiner system throughout Japan that is currently in practice only in the Metropolis of Tokyo and Yokohama, Nagoya, Osaka and Kobe Cities in order to incorporate forensic training in the postgraduate clinical training programs that will become compulsory in 2004.

Attitude of Health Personnel↗
PubMed2000

Differences in muscle cross-sectional area and strength between elite senior and college Olympic weight lifters.

BACKGROUND: The purpose of this study was to investigate the profiles of muscle cross-sectional area (CSA) and strength capability in relation to lifting ability in Olympic weight lifters. METHODS: The subjects were 8 elite senior lifters (ESL, age=25.2+/-1.3 years, height=1.64+/-0.03 m, mass=68.6+/-4.2 kg, mean+/-SEM) and 9 college lifters (CL, 20.8+/-0.3 years, 1.67+/-0.03 m, 70.53.4 kg) whose predetermined weight classes were within the same range. The CSAs of elbow or knee extensor and elbow or knee flexor muscles were measured using a B-mode ultrasound apparatus. Concentric and eccentric maximal voluntary forces were determined with an isokinetic dynamometer at a constant velocity of 1.05 rad/sec. RESULTS: The best score of the total mass lifted in the snatch and the clean and jerk lifts was significantly higher in ESL than in CL even in terms of per unit of fat-free mass. There were no significant differences between the two groups in fat-free mass, muscle CSA and force values with the exception that ESL compared to CL showed significantly greater force in concentric knee flexion. However, the ratios of force to muscle CSA (F/CSAs) in concentric and eccentric elbow extensions, eccentric knee extension and concentric knee flexion were significantly higher in ESL than in CL. CONCLUSIONS: The present results indicated that the magnitude of muscular development in limbs was similar in elite senior and college lifters whose predetermined weight classes were within the same range. As compared to college lifters, however, elite senior lifters had a higher F/CSA in specific muscle action modes, which might relate to the optimal execution of the Olympic lifts.

Anthropometry↗
PubMed2000

Changes in muscle size and architecture following 20 days of bed rest.

Five healthy men carried out a program of head-down bed rest (BR) for 20 days. Before and after BR, a series of cross-sectional scans of the thigh were performed using magnetic resonance imaging, from which volumes of the quadriceps muscles were determined and physiological cross-sectional areas (PCSA) were calculated. Muscle thickness and pennation angles of the triceps brachii, vastus lateralis, and triceps surae muscles were also determined by ultrasonography. During BR, subjects performed unilateral isokinetic knee extension exercises every day. The contralateral limb served as a control. Decrease in PCSA after BR was greater in the control (-10.2 +/- 6.3%) than in the trained limb (-5.2 +/- 4.2%). Among the quadriceps, vastus intermedius in the control limb was predominantly atrophied by BR with respect to the volume and PCSA, and the rectus femoris showed the greatest training effect and retained its size in the trained limb. Decreases in muscle thicknesses in leg muscles were not prevented by the present exercise protocol, suggesting a need for specific exercise training for these muscles. Neither trained nor control muscles showed significant changes in pennation angles in any muscles after BR, suggesting that muscle architecture does not change remarkably by muscle atrophy by up to 10%.

Adult↗
PubMed1999

The effects of long-term bed rest on H-reflex and motor evoked potential in the human soleus muscle during standing.

H-reflex and motor evoked potential (MEP) induced by transcranial magnetic stimulation (TMS) in soleus muscle of five normal subjects were investigated before and after 20 days 6 degree head-down bed rest (BR). Soleus H-reflex during standing following bed rest decreased in all five subjects. The size of the maximum H-reflex (Hmax), expressed as a percentage of the maximum M-response (Mmax), decreased from 63.3+/-23.3% before BR to 26.7+/-12.5% after BR. However, there were no significant differences between MEPs before and after bed rest. Moreover, MEP/Hmax after bed rest was larger than before bed rest in all subjects. These results indicate a strong inhibition of H-reflex and no adaptation of MEP in soleus muscle during standing following bed rest.

Electromyography↗
PubMed1999

Estimation of stress in child neglect from thymic involution.

It is difficult to evaluate the extent of stress in cases of suspected child abuse/neglect in a medico-legal autopsy. We have previously reported that stress due to abuse/neglect was found to have led to thymic involution. To elucidate the influence upon thymocytes differentiation, we compared the proportion of the thymocyte subpopulation in the thymus of a neglected child with one in an age-matched control obtained from cardiac surgery. We found that the relative number of CD4+ CD8+ double positive (DP) thymocytes decreased in the neglected child. It was presumed that the selective decrease in the number of the immature DP thymocytes with CD3- to low bcl-2low caused the thymic involution in the neglected child. It was suggested that an alteration in the proportion of thymocytes subpopulation might be used as an index of stress in cases of child abuse/neglect.

Autopsy↗
PubMed1999

Pervanadate activates NADPH oxidase via protein kinase C-independent phosphorylation of p47-phox.

We studied differences between the NADPH oxidase activation pathways triggered by pervanadate, a protein tyrosine phosphatase inhibitor, and phorbol 12-myristate 13-acetate (PMA), a protein kinase C activator, in guinea pig neutrophils. Previously, pervanadate has been shown to activate NADPH oxidase via the tyrosine kinase-dependent pathway (Yamaguchi et al. Arch. Biochem. Biophys. 323, 382-386, 1995). Both pervanadate and PMA induced superoxide anion (O-2) production, translocation of the 47-kDa protein component of the phagocyte oxidase (p47-phox) to the plasma membrane, and phosphorylation of p47-phox in the membrane. A selective protein kinase C inhibitor, GF 109203X, markedly inhibited PMA-induced O-2 production, p47-phox translocation, and p47-phox phosphorylation, but did not inhibit pervanadate-induced O-2 production and only slightly suppressed pervanadate-induced translocation and phosphorylation. These results demonstrate that pervanadate activates NADPH oxidase independently of protein kinase C. Phosphopeptide mapping of p47-phox revealed differences in the mechanism between pervanadate-induced and PMA-induced phosphorylation. Furthermore, some protein kinases which phosphorylate p47-phox-derived peptide are activated by pervanadate. These results suggest the existence of novel protein kinases responsible for the phosphorylation of p47-phox and the activation of these protein kinases by tyrosine kinase.

Amino Acid Sequence↗
PubMed1999

Revascularization and new bone formation in heat-treated bone grafts.

Human imnmunodeficiency virus (HIV) infection is one of the possible serious complications associated with bone allografts. In order to prevent infection, grafted bone is sterilized by various treatments. Heat treatment has attracted attention as a simple and practical method. We carried out a histological study of the influence of heat treatment on autogenic bone grafts. To eliminate the problem of antigenicity of grafted bone, we used autografts, not allografts. Three types of heat-treated autografts were employed: heat-treated at 60 degrees C for 30 min, at 80 degrees C for 10 min, and at 100 degrees C for 5 min; as a control, fresh autografts were replaced in the rabbits' ilium. One, 2, 4 and 8 weeks after grafting, we performed microangiography and prepared two types of samples: transparent and haematoxylin-eosin (H&E) stained. Then, using an image analyzer, we quantitatively measured revascularization and new bone formation in the grafted bone. The grafts heat-treated at 60 degrees C showed early and good revascularization and new bone formation, from 1 to 8 weeks. The grafts heat-treated at 80 degrees C showed relatively good revascularization and new bone formation. However, the grafts heat-treated at 100 degrees C showed unsatisfactory revascularization and bone formation, less than 40% of control 8 weeks after grafting. Therefore, heat treatment at 60-80 degrees C does not seriously affect revascularization and new bone formation.

Animals↗
PubMed1999

Profiles of musculoskeletal development in limbs of college Olympic weightlifters and wrestlers.

To investigate the event-related profiles of musculoskeletal development in weight-categorized athletes, we measured the cross-sectional areas (CSA) of bone and muscle in the forearm, upper arm, lower leg and thigh, using a B-mode ultrasound apparatus, in college Olympic weightlifters (OWL, n = 19) and wrestlers (WR, n = 17) and untrained men (UM, n = 24), whose body masses were within the range from 55 kg to 78 kg. Both bone and muscle CSA at all sites were significantly correlated to the two-thirds power of fat-free mass (FFM(2/3)) with correlation coefficients of 0.430-40.741 (P < 0.05) and 0.608-0.718 (P < 0.05), respectively. Moreover, there were significant correlations between bone and muscle CSA at all sites (r = 0.664-0.829, P < 0.05). Even when bone and muscle CSA were expressed relative value to FFM(2/3), both OWL and WR showed significantly greater values than UM at all sites except for the lower leg. Furthermore, the comparison of the lean (bone + muscle) CSA ratio from site to site indicated a higher distribution of lean tissues in the upper extremities in OWL and WR compared to UM. While there was no significant difference between the two athlete groups in FFM(2/3), OWL showed significantly larger values than WR in the bone CSA of the upper arm and thigh and in the muscle CSA of the lower leg and thigh. However, lean CSA ratios of the upper extremities to the lower ones were significantly higher in WR than in OWL. Thus, the present results indicated that, compared to UM, OWL and WR had a greater lean tissue CSA in limbs, especially in the upper extremities, even when the difference in FFM was normalized. Moreover, the relative distribution of lean tissues in limbs differed between the two weight-categorized athletes in spite of there being no difference in FFM, which may be attributable to their own training regimens and/or competition style.

Adult↗
PubMed1999

Non-uniform mechanical activity of quadriceps muscle during fatigue by repeated maximal voluntary contraction in humans.

To determine the non-uniform surface mechanical activity of human quadriceps muscle during fatiguing activity, surface mechanomyogram (MMG), or muscle sound, and surface electromyogram (EMG) were recorded from the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM) muscles of seven subjects during unilateral isometric knee extension exercise. Time- and frequency-domain analyses of MMG and of EMG fatigued by 50 repeated maximal voluntary contractions (MVC) for 3 s, with 3-s relaxation in between, were compared among the muscles. The mean MVC force fell to 49.5 (SEM 2.0)% at the end of the repeated MVC. Integrated EMG decreased in a similar manner in each muscle head, but a marked non-uniformity was found for the decline in integrated MMG (iMMG). The fall in iMMG was most prominent for RF, followed by VM and VL. Moreover, the median frequency of MMG and the relative decrease in that of EMG in RF were significantly greater (P < 0.05) than those recorded for VL and VM. These results would suggest a divergence of mechanical activity within the quadriceps muscle during fatiguing activity by repeated MVC.

Adult↗
PubMed1999

Tissue-specific expression of Le(Y) antigen in high endothelial venules of human lymphoid tissues.

In this study, we demonstrated that the anti-Le(Y) antibody (BM-1) especially reacted with high endothelial venules (HEVs) in peripheral lymph nodes of blood group O individuals. The Le(Y) expression on HEVs showed a unique tissue-specific pattern, i.e., a large amount of the Le(Y) expression in peripheral lymph nodes and no or small amounts in mesenteric lymph node. Statistical analysis showed that there was the significant difference between the percentage of Le(Y)-positive HEVs in peripheral lymph nodes and mesenteric lymph nodes. No expression of Le(Y) was observed in vessels of Payer's patch, thymus, spleen and other non-lymphoid organs. In blood group A or B individuals, the reactivity between HEVs and anti-Le(Y) antibody increased after enzyme digestion with alpha-N-acetylgalactosaminidase or alpha-galactosidase. These findings show that the expression of difucosylated blood group ABH antigens are especially expressed on HEVs in peripheral lymph nodes. Furthermore, the tissue-specific pattern suggests that these antigens may be related to intercellular adhesion between lymphocytes and HEVs.

ABO Blood-Group System↗
PubMed1999

Human parathymic lymph node: morphological and functional significance.

Parathymic lymph nodes (PTLNs) have been identified in several species, but in humans they have been noted only once before in a study 90 years ago using fetal material. We now report their occurrence in children. Human PTLNs are small but distinctive lymphatic organs located on the surface of the thymus (or sometimes between the upper and lower lobes of the thymus) and covered with the thymic capsule. Histologically, the medullary cords of these lymph nodes were found to be thin, with only small numbers of plasma cells. In addition, they had a well-developed paracortical area rich with high endothelial venules (HEV), but a thin cortex, including only a few undeveloped follicles. Flow cytometric analysis of PTLNs revealed that the ratios of T:B cells (14.6+/-9.3) and of CD4+:CD8+ T cells (4.9+/-1.4) in PTLNs were much higher than in other peripheral lymphoid tissues and in peripheral blood. Because of these characteristics of the human PTLNs, we propose that the human PTLNs might influence the functional differentiation of T cells.

Antigens, CD19↗
PubMed1999

Velocity associated characteristics of force production in college weight lifters.

OBJECTIVE: To determine velocity specific isokinetic forces and cross sectional areas of reciprocal muscle groups in Olympic weight lifters. METHODS: The cross sectional area of the flexor or extensor muscles of the elbow or knee joint was determined by a B-mode ultrasonic apparatus in 34 college weight lifters and 31 untrained male subjects matched for age. Maximum voluntary force produced in the flexion and extension of the elbow and knee joints was measured on an isokinetic dynamometer at 60, 180, and 300 degrees/s. RESULTS: The average cross sectional area was 31-65% higher, and the force was 19-62% higher in weight lifters than in the untrained subjects. The ratio of force to cross sectional area was the same in both groups. The weight lifters showed a lower velocity associated decline in force than untrained subjects in the elbow and knee flexors but not in the extensors. CONCLUSIONS: These results indicate that for muscle contractions with velocities between 60 degrees/s and 300 degrees/s the difference in isokinetic force between weight lifters and untrained subjects can be primarily attributed to the difference in the muscle cross sectional area. However, the lower velocity associated decline in force implies that weight lifters may have a higher force per cross sectional area than untrained subjects at velocities above 300 degrees/s.

Acceleration↗
PubMed1999

Resistance training affects GLUT-4 content in skeletal muscle of humans after 19 days of head-down bed rest.

This study assessed the effects of inactivity on GLUT-4 content of human skeletal muscle and evaluated resistance training as a countermeasure to inactivity-related changes in GLUT-4 content in skeletal muscle. Nine young men participated in the study. For 19 days, four control subjects remained in a -6 degrees head-down tilt at all times throughout bed rest, except for showering every other day. Five training group subjects also remained at bed rest, except during resistance training once in the morning. The resistance training consisted of 30 isometric maximal voluntary contractions for 3 s each; leg-press exercise was used to recruit the extensor muscles of the ankle, knee, and hip. Pauses (3 s) were allowed between bouts of maximal contraction. Muscle biopsy samples were obtained from the lateral aspect of vastus lateralis (VL) muscle before and after the bed rest. GLUT-4 content in VL muscle of the control group was significantly decreased after bed rest (473 +/- 48 vs. 398 +/- 66 counts. min-1. microgram membrane protein-1, before and after bed rest, respectively), whereas GLUT-4 significantly increased in the training group with bed rest (510 +/- 158 vs. 663 +/- 189 counts. min-1. microgram membrane protein-1, before and after bed rest, respectively). The present study demonstrated that GLUT-4 in VL muscle decreased by approximately 16% after 19 days of bed rest, and isometric resistance training during bed rest induced a 30% increase above the value of GLUT-4 before bed rest.

Adult↗