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Biomedical subjects

N Fujimaki

Publications and source records attributed to N Fujimaki.

At least 19 recordsLinked to original sources
PubMed2001

Localization of plectin and other related proteins along the sarcolemma in smooth muscle cells of rat colon.

Plectin is a versatile linker protein which is associated with various types of cytoskeletal components and/or filaments including intermediate filaments. To better understand the functional roles of plectin in smooth muscle cells, we examined the distribution of plectin and other related proteins in rat colon smooth muscles by confocal laser and electron microscopy. The sarcolemma of smooth muscle cells exhibits two ultrastructurally distinct domains, domains associated with dense plaques and caveola-rich domains. Staining with anti-plectin and anti-desmin antibodies showed that plectin was localized along the sarcolemma in an intermittent manner and desmin was distributed in the sarcoplasm and intermittently at the cell periphery where it was codistributed with desmin. Plectin exhibited complementary and non-overlapping distribution to caveolin-1 and dystrophin, components of caveola domains, whereas plectin was codistributed with vinculin, talin and integrin beta1, components of dense plaques. Plectin was also codistributed with beta2-chain laminin but not with beta1-chain laminin. Electron microscopic observations on the sarcolemma revealed close association of intermediate filaments with dense plaques. Correlated confocal and electron microscopy clearly demonstrated that anti-plectin fluorescence corresponded to dense plaques but not to caveola domains in electron microscopic images. These findings indicate that plectin is confined to dense plaques to which desmin intermediate filaments may be anchored in rat colon smooth muscle cells.

Animals↗
PubMed2001

Morphological changes and recovery process in the tenotomized soleus muscles of the rat.

Tenotomized soleus muscles of adult rats were analyzed morphologically and biochemically with special reference to the recovery process. Light microscopic observations of semi-thin sections showed that the characteristic central core lesion was most extensive at 1 week after tenotomy and began to diminish in extent at 2 weeks until no trace of lesion could be seen by 6th week, as confirmed by thin-section electron microscopy. Three phases of changes in the cross-sectional area of muscle fibers after tenotomy were demonstrated by morphometry: phase I designated as the initial increase up to the 3rd day, phase II as the progressive decrease until the 4th week, and phase III as the recovery to normal or even hypertrophy. In electron microscopy, the earliest alteration of myofibrils was recognized at 3 days after tenotomy. The Z discs showed a wavy or zigzag profile with frequent longitudinal splitting of myofibrils. From the 2nd week on, muscle fibers underwent a process of recovery, replacing the central core lesion with new myofibrils in which a reassembly of thick filaments into bundles of thin filaments took place, with Z discs being aligned adjacent to the peripheral complete myofibrils. In SDS-polyacrylamide gel electrophoresis, the molar ratio of myosin to actin diminished markedly as the central core lesion developed and gradually returned to normal with time, correlating well with the loss and subsequent reassembly of thick filaments.

Actins↗
PubMed2001

Formation of unique vacuoles in tenotomized rat soleus muscle fibers.

The formation of unique vacuoles in tenotomized rat soleus muscle fibers was examined by light and electron microscopy. After tenotomy at both proximal and distal tendons, virtually all muscle fibers underwent characteristic degenerative changes with a disorganization of myofibrils called the central core lesion, but eventually recovered. At 3 days after tenotomy, some muscle fibers showed small vacuoles in the sarcoplasm of the end segments, which were larger in diameter and paler in staining than those of the control fibers in light microscopy. At 5 days, more fibers formed larger vacuoles together with the extensive disorganization of myofibrils. Such vacuole formation was more conspicuous in the distal end than in the proximal end. At 1 week the myofibrillar disorganization was most extensive in the central areas, and vacuoles were considerably enlarged in some fibers to occupy most of the sarcoplasm near the fiber ends. Vacuoles decreased in number and size with time and could rarely be seen at 4 weeks postoperative. In thin-section electron microscopy, the early forms of vacuoles were often connected with the T-system tubules. The limiting membrane of such vacuoles possessed many caveolae, some of which appeared to be continuous with the T-system networks. The vacuole membrane was closely associated with the sarcoplasmic reticulum to form dyadic connections. In later stages, the vacuole membrane was lined in part with the basal lamina. From these findings, it can be concluded that the vacuoles are sarcolemmal in nature and derived from the T-system. The significances of the vacuole formation are discussed with special reference to the mechanism and fate of the vacuoles and their clinical implications.

Animals↗
PubMed2000

Actin bundles in perineurial cells of rat spinal nerves.

The overall distribution of the actin cytoskeleton in perineurial cells of rat spinal nerves was examined by confocal laser and thin-section electron microscopy. Confocal laser microscopy of whole-mount nerves stained with fluorescent-labelled phalloidin revealed two types of actin bundles in perineurial cells; stress fiber-type actin bundles and circumferential actin bundles. The degree of development of the actin cytoskeleton varied in different segments of different nerves. Stress fiber-type actin bundles were also immunostained for myosin and vinculin and were well-developed in the perineurial cells of large-sized nerves and dorsal root ganglia, whereas they were poor in spinal nerve root sheaths within the subarachnoid space. In peripheral nerves, stress fiber-type actin bundles tended to be arranged transverse to the nerve axis. Circumferential actin bundles were localized along intercellular junctions, which were immunostained with several junctional proteins such as alpha-catenin, occludin and ZO-1. Thin-section electron microscopy confirmed the distribution pattern of actin bundles observed by confocal laser microscopy. These findings suggest that actin bundles may play some roles in structurally stabilizing the perineurium by providing mechanical support for the cell layers as well as cell junctions to maintain perineurial integrity and form diffusion barriers in peripheral nerves.

Actin Cytoskeleton↗
PubMed2000

Relation among portal segmentation, proper hepatic vein, and external notch of the caudate lobe in the human liver.

OBJECTIVE: To identify portal segmentation and a portal fissure in the caudate lobe of the human liver in relation to the hepatic venous system and the external notch at the caudal edge of the caudate lobe. SUMMARY BACKGROUND DATA: Although the anatomy of the caudate lobe has been studied, the detailed anatomy has not yet been clarified; this is necessary to develop safe procedures for caudate lobe resection. METHODS: A total of 88 formalin-fixed human livers were dissected to visualize the portal vein and hepatic vein systems of the caudate lobe in relation to the external notch. RESULTS: The patterns of portal branching were classified into two types. In 58 livers (67.4%), the territories of the first-order portal branches were clearly divided into two areas (the Spiegel lobe and the paracaval portion). In the remaining 28 livers (32.6%), the territories of the second-order portal branches were clearly divided into two areas. These two areas were distinctly separated by an internal plane, which was coincident with the external notch. The caudate lobe had a systematized hepatic venous system that consisted of one (87.5%) or two (11.4%) proper hepatic veins and plural accessory hepatic veins. The proper hepatic veins laid along the internal plane between these two portal areas. CONCLUSION: The caudate lobe exhibited distinct portal segmentation with a portal fissure that was indicated internally by the proper hepatic vein and externally by the notch at the caudal edge of the caudate lobe.

Adult↗
PubMed2000

Estimating neural sources from each time-frequency component of magnetoencephalographic data.

We have developed a method that incorporates the time-frequency characteristics of neural sources into magnetoencephalographic (MEG) source estimation. This method, referred to as the time-frequency multiple-signal-classification algorithm, allows the locations of neural sources to be estimated from any time-frequency region of interest. In this paper, we formulate the method based on the most general form of the quadratic time-frequency representations. We then apply it to two kinds of nonstationary MEG data: gamma-band (frequency range between 30-100 Hz) auditory activity data and spontaneous MEG data. Our method successfully detected the gamma-band source slightly medial to the N1m source location. The method was able to selectively localize sources for alpha-rhythm bursts at different locations. It also detected the mu-rhythm source from the alpha-rhythm-dominant MEG data that was measured with the subject's eyes closed. The results of these applications validate the effectiveness of the time-frequency MUSIC algorithm for selectively localizing sources having different time-frequency signatures.

Acoustic Stimulation↗
PubMed2000

Induction of oxidatively modified proteins in skeletal muscle by electrical stimulation and its suppression by dietary supplementation of (-)-epigallocatechin gallate.

The oxidative stress produced by electrical stimulation-induced muscle contraction was examined in the skeletal muscle proteins of rats that had been fed on the dietary flavonoid, (-)-epigallocatechin gallate (EGCg). Electrical stimulation of the rat leg muscle every second day for a two-week period resulted in an increased (p < 0.05) muscle weight and accumulation of oxidatively induced modified proteins. Similar stimulation conducted every day for only one week had no effect on the muscle weight or protein oxidation, although the rate of protein degradation increased. Rats fed on a 20% casein diet supplemented with 0.1% EGCg for 2 weeks responded to the electrical stimulation of muscle contraction by reducing the increased muscle protein carbonyl content when compared to their counterparts fed on a control diet. There was no change in activity of antioxidative enzymes in muscle tissue of the EGCg-fed rats receiving electrical stimulation. The results of this study show that the antioxidative property of EGCg was effective for suppressing oxidative modification of the skeletal muscle protein induced by electrical stimulation. This finding demonstrates that EGCg has a beneficial effect in vivo on the free radical-mediated oxidative damage to muscle proteins.

Animals↗
PubMed1999

Presupplementary motor area activation during sequence learning reflects visuo-motor association.

In preceding studies (Hikosaka et al., 1996; Sakai et al., 1998) we have shown that the presupplementary motor area (pre-SMA), an anterior part of the medial premotor cortex, is active during visuo-motor sequence learning. However, the paradigm required the subjects first to acquire correct visuo-motor association and then to acquire correct sequence, and it was still unknown which of the two processes the pre-SMA is involved in. To further characterize the role of pre-SMA, we have conducted another series of functional magnetic resonance imaging experiments using three learning paradigms. The three were the same in that they involved a visuo-motor association component, but they differed in terms of the involvement of sequential components; one involved no sequence learning, whereas the other two involved learning of motor sequence or perceptual sequence. Comparison of the learning conditions with the any-order button press condition revealed pre-SMA activation in all three paradigms. The pre-SMA activation remained unchanged during learning of visuo-motor associations but decreased during learning of sequences, suggesting that the pre-SMA is related to visuo-motor association rather than sequence. The decrease of pre-SMA activation in the sequential paradigms may reflect the process by which individual visuo-motor associations were replaced by the formation of sequential procedural memory, which occurs outside the pre-SMA. Thus activation of the pre-SMA was related to the extent to which the task performance depended on conscious visuo-motor associations.

Adult↗
PubMed1999

Functional magnetic resonance imaging of neural activity related to orthographic, phonological, and lexico-semantic judgments of visually presented characters and words.

Functional magnetic resonance imaging was used to investigate neural activity during the judgment of visual stimuli in two groups of experiments using seven and five normal subjects. The subjects were given tasks designed differentially to involve orthographic (more generally, visual form), phonological, and lexico-semantic processes. These tasks included the judgments of whether a line was horizontal, whether a pseudocharacter or pseudocharacter string included a horizontal line, whether a Japanese katakana (phonogram) character or character string included a certain vowel, or whether a character string was meaningful (noun or verb) or meaningless. Neural activity related to the visual form process was commonly observed during judgments of both single real-characters and single pseudocharacters in lateral extrastriate visual cortex, the posterior ventral or medial occipito-temporal area, and the posterior inferior temporal area of both hemispheres. In contrast, left-lateralized activation was observed in the latter two areas during judgments of real- and pseudo-character strings. These results show that there is no katakana "word form center" whose activity is specific to real words. Activation related to the phonological process was observed, in Broca's area, the insula, the supramarginal gyrus, and the posterior superior temporal area, with greater activation in the left hemisphere. These activation foci for visual form and phonological processes of katakana also were reported for the English alphabet in previous studies. The present activation showed no additional areas for contrasts of noun judgment with other conditions and was similar between noun and verb judgment tasks, suggesting two possibilities: no strong semantic activation was produced, or the semantic process shared activation foci with the phonological process.

Adult↗
PubMed1999

Plectin is a linker of intermediate filaments to Z-discs in skeletal muscle fibers.

Plectin is a versatile linker protein which is associated with various types of cytoskeletal components and/or filaments including intermediate filaments, and its deficiency causes the disruption of myofibrils, or muscular dystrophy. To better understand the functional role of plectin in skeletal muscle fibers, we have examined the topological and structural relationships of plectin to intermediate filaments and Z-discs in rat diaphragm muscles by confocal and immunoelectron microscopy. Immunofluorescence analysis revealed that plectin was colocalized with desmin at the periphery of Z-discs. This plectin localization around Z-discs was constantly maintained irrespective of the contracted or extended state of the muscle fibers, suggesting either direct or indirect association of plectin with Z-discs. Immunogold labeling in skinned muscle fibers clearly demonstrated that plectin-labeled fine threads linked desmin intermediate filaments to Z-discs and connected intermediate filaments to each other. These results indicate that through plectin threads desmin intermediate filaments form lateral linkages among adjacent Z-discs, preventing individual myofibrils from disruptive contraction and ensuring effective force generation.

Animals↗
PubMed1998

Separate cerebellar areas for motor control.

Cerebellar activation was measured using functional magnetic resonance imaging, while seven normal subjects tapped their fingers paced by tone sequences with or without tone omission. The cerebellar anterior lobe (Larsell's H IV-V) ipsilateral to the movement was activated to a similar degree irrespective of the presence or absence of the tone omission. In contrast, the lateral part of the bilateral posterior lobe (H VIIa) was significantly highly activated for the tone sequence with random omission, compared with either that without omission or that with regular omission. The result suggests that the H IV-V is involved in motor execution, while the lateral part of H VIIa is involved in on-line motor adjustment to unpredictable sensory stimuli.

Acoustic Stimulation↗
PubMed1998

Attention-regulated activity in human primary visual cortex.

Effects of attention to a local contour of a moving object on the activation of human primary visual cortex (area V1) were examined. Local cerebral oxygenation changes (an index of neuronal activity) in human area V1 were measured with functional magnetic resonance imaging (fMRI) in conditions including the following two: 1) when attention was selectively directed toward one side of a moving wedge (the attention condition) and 2) when the wedges were viewed passively (the passive condition). Activation in area V1 was found to be higher in the attention condition than in the passive condition. To our knowledge, this is the first finding that attention to motion activates as early as area V1. We suggest that attentional activation of area V1 is task dependent.

Attention↗
PubMed1998

The direct visualization of structural array from laminin to dystrophin in sarcolemmal vesicles prepared from rat skeletal muscles.

It has been biochemically shown that dystrophin and alpha- and beta-dystroglycan form an oligomeric complex which links laminin, a component of the basement membrane, to components of the subsarcolemmal cytoskeleton in skeletal muscle fibers. In the present study the dystrophin-glycoprotein complex and its structural relationships to laminin and subsarcolemmal cytoskeleton were ultrastructurally examined in crude surface membranes prepared from rat skeletal muscles. Sarcolemmal vesicles within crude surface membranes were identified and characterized by fine protrusions on their outer surface and electron-dense materials or patches associated with the inner surface. These two components were seen to be in register with each other across the sarcolemma. The fine protrusions were immunolabeled by anti-alpha-dystroglycan and reassociated with exogenous laminin. Immunolabeling in combination with laminin reassociation demonstrated that the electron-dense materials contained dystrophin at laminin-binding domains of the membrane. In addition, they were often associated with very fine filaments. These results provide morphological evidence for the biochemically proposed model of molecular array of dystrophin complex from the basement membrane to the subsarcolemmal cytoskeleton.

Animals↗
PubMed1996

Magnetoencephalographic study on the cerebral neural activities related to the processing of visually presented characters.

Neuromagnetic fields were recorded from normal subjects to study the time course of cerebral neural activation while they performed a matching task of visual stimuli in which sequentially presented Japanese characters or unreadable pseudo-characters were compared according to phonological (reading of the characters) or graphical (geometry of the pseudo-characters) identity. In response to the single real-character or pseudo-character which was presented the latest distinct magnetic field components were observed, from which current dipole sources of the fields were localized in the individual magnetic resonance images of the brain. In the phonological identification, the sources were found in the parieto-occipital extrastriate cortex at 155-210 ms following the character presentation, and in the posterior temporal region (part of the Wernicke's area) and the posterior superior temporal region of the visual/auditory association cortex at 210-410 ms. The activity in these temporal regions was left hemisphere dominant, and may be the neural basis of phonological processing of the visual characters. In the graphical identification, sources occurring at 125-250 ms were noted in the inferior temporo-occipital region, and those at 180-460 ms in the posterior temporal and posterior superior temporal regions of the right hemisphere. These results indicate that the activities in the temporal area are lateralized to the left for the phonological processing and to the right for the graphical processing.

Adult↗
PubMed1995

Event-related magnetic fields at latencies of over 400 ms in silent reading of Japanese Katakana meaningless words.

Event-related magnetic fields (ERFs) were recorded when subjects were presented with meaningless readable words or unreadable words. The ERF averages for readable words and those for unreadable words showed a large difference at latencies of over 400 ms. The equivalent current dipoles were obtained only for readable words, and were located near the cingulate gyrus and the supplementary motor area whose functions are considered to be related to attention and motor planning.

Adult↗
PubMed1994

Event-related potentials in silent speech.

Event-related potentials (ERPs) in silent speech using the vowel /a/ were recorded from 12 scalp electrodes and three electrodes monitoring eye and throat movements in eight subjects cued by one of two randomly lit light-emitting diodes (LEDs). The average silent-speech potential minus nonsilent-speech potential showed two significant scalp potential distributions--a positive difference in the occipital scalp area at a 0.30-s latency from the LED onset and a negative difference in the frontal scalp area peaking at electrode Fz at a 0.42-s latency. The occipital scalp potential may include an endogenous component like P3. Possible sites of neural activities underlying the frontal negative difference are discussed in relation to the topography of the scalp potential and functions involved in silent speech.

Adolescent↗