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Biomedical subjects

Masaki Fukunaga

Publications and source records attributed to Masaki Fukunaga.

At least 19 recordsLinked to original sources
PubMed2021

1q21.1 distal copy number variants are associated with cerebral and cognitive alterations in humans.

Low-frequency 1q21.1 distal deletion and duplication copy number variant (CNV) carriers are predisposed to multiple neurodevelopmental disorders, including schizophrenia, autism and intellectual disability. Human carriers display a high prevalence of micro- and macrocephaly in deletion and duplication carriers, respectively. The underlying brain structural diversity remains largely unknown. We systematically called CNVs in 38 cohorts from the large-scale ENIGMA-CNV collaboration and the UK Biobank and identified 28 1q21.1 distal deletion and 22 duplication carriers and 37,088 non-carriers (48% male) derived from 15 distinct magnetic resonance imaging scanner sites. With standardized methods, we compared subcortical and cortical brain measures (all) and cognitive performance (UK Biobank only) between carrier groups also testing for mediation of brain structure on cognition. We identified positive dosage effects of copy number on intracranial volume (ICV) and total cortical surface area, with the largest effects in frontal and cingulate cortices, and negative dosage effects on caudate and hippocampal volumes. The carriers displayed distinct cognitive deficit profiles in cognitive tasks from the UK Biobank with intermediate decreases in duplication carriers and somewhat larger in deletion carriers-the latter potentially mediated by ICV or cortical surface area. These results shed light on pathobiological mechanisms of neurodevelopmental disorders, by demonstrating gene dose effect on specific brain structures and effect on cognitive function.

Brain↗
PubMed2006

An adaptive filter for suppression of cardiac and respiratory noise in MRI time series data.

The quality of MRI time series data, which allows the study of dynamic processes, is often affected by confounding sources of signal fluctuation, including the cardiac and respiratory cycle. An adaptive filter is described, reducing these signal fluctuations as long as they are repetitive and their timing is known. The filter, applied in image domain, does not require temporal oversampling of the artifact-related fluctuations. Performance is demonstrated for suppression of cardiac and respiratory artifacts in 10-minute brain scans on 6 normal volunteers. Experimental parameters resemble a typical fMRI experiment (17 slices; 1700 ms TR). A second dataset was acquired at a rate well above the Nyquist frequency for both cardiac and respiratory cycle (single slice; 100 ms TR), allowing identification of artifacts specific to the cardiac and respiratory cycles, aiding assessment of filtering performance. Results show significant reduction in temporal standard deviation (SD(t)) in all subjects. For all 6 datasets with 1700 ms TR combined, the filtering method resulted in an average reduction in SD(t) of 9.2% in 2046 voxels substantially affected by respiratory artifacts, and 12.5% for the 864 voxels containing substantial cardiac artifacts. The maximal SD(t) reduction achieved was 52.7% for respiratory and 55.3% for cardiac filtering. Performance was found to be at least equivalent to the previously published RETROICOR method. Furthermore, the interaction between the filter and fMRI activity detection was investigated using Monte Carlo simulations, demonstrating that filtering algorithms introduce a systematic error in the detected BOLD-related signal change if applied sequentially. It is demonstrated that this can be overcome by combining physiological artifact filtering and detection of BOLD-related signal changes simultaneously. Visual fMRI data from 6 volunteers were analyzed with and without the filter proposed here. Inclusion of the cardio-respiratory regressors in the design matrix yielded a 4.6% t-score increase and 4.0% increase in the number of significantly activated voxels.

Adult↗
PubMed2006

Toward a common circle: interhemispheric contextual modulation in human early visual areas.

Humans can readily and effortlessly perceive a rich, stable, and unified visual world from a complex visual scene. Yet our internal representation of a visual object appears to be sparse and fragmented. How and where in the brain are such fragmented representations organized into a whole percept? Recent studies have accumulated evidence that some global feature integration is mediated at the early stage of visual processing. However, the spatial operating range of the integration still remains unclear. The present human functional magnetic resonance imaging study provides support that the global integration process in early visual areas, including even the primary visual area V1, is mediated beyond the separated projection of visual hemifields from right and left sides of the fixation to the visual cortex of the contralateral cerebral hemisphere. Retinotopic neural responses corresponding to a visual target were significantly enhanced when another target was simultaneously presented at the point-symmetrical position in the nonassociated visual field quadrant. The result makes a convincing case that the contextual effects involve feedback from higher areas, because there are no direct callosal connections that allow such interhemispheric contextual modulation. This enhancement from the ipsilateral hemifield may help rapid position-and-size-invariant detection of a circular pattern, which may be special among visual structures because of its ubiquity in natural scenes. Early visual areas as well as higher ones may play a more essential role in perceiving the unity of the real world than previously thought.

Adult↗
PubMed2006

Large-amplitude, spatially correlated fluctuations in BOLD fMRI signals during extended rest and early sleep stages.

A number of recent studies of human brain activity using blood-oxygen-level-dependent (BOLD) fMRI and EEG have reported the presence of spatiotemporal patterns of correlated activity in the absence of external stimuli. Although these patterns have been hypothesized to contain important information about brain architecture, little is known about their origin or about their relationship to active cognitive processes such as conscious awareness and monitoring of the environment. In this study, we have investigated the amplitude and spatiotemporal characteristics of resting-state activity patterns and their dependence on the subjects' alertness. For this purpose, BOLD fMRI was performed at 3.0 T on 12 normal subjects using a visual stimulation protocol, followed by a 27 min rest period, during which subjects were allowed to fall asleep. In subjects who were asleep at the end of the scan, we found (a) a higher amplitude of BOLD signal fluctuation during rest compared with subjects who were awake at the end of the scan; (b) spatially independent patterns of correlated activity that involve all of gray matter, including deep brain nuclei; (c) many patterns that were consistent across subjects; (d) that average percentage levels of fluctuation in visual cortex (VC) and whole brain were higher in subjects who were asleep (up to 1.71% and 1.16%, respectively) than in those who were awake (up to 1.15% and 0.96%) at the end of the scan and were comparable with those levels evoked by intense visual stimulation (up to 1.85% and 0.76% for two subject groups); (e) no confirmation of correlation, positive or negative, between thalamus and VC found in earlier studies. These findings suggest that resting-state activity continues during sleep and does not require active cognitive processes or conscious awareness.

Adult↗
PubMed2006

Pretreatment of sivelestat sodium hydrate improves the lung microcirculation and alveolar damage in lipopolysaccharide-induced acute lung inflammation in hamsters.

Damage to the lung microcirculation and alveoli caused by activated leukocytes is known to play an important role in the development of acute lung injury (ALI). The aim of this study is to evaluate the difference in the effect of pretreatment and posttreatment of a synthetic neutrophil elastase inhibitor sivelestat on ALI. Hamsters were instilled with 10.0 mg/kg of lipopolysaccharide (LPS) intratracheally for 1 h to simulate ALI. Two milligrams per kilogram of sivelestat was injected intraperitoneally either previously or after LPS infusion. One and 24 hours after the infusion of LPS, pulmonary microcirculation was observed under the intravital microscopy. In another series, the blood cell counts were evaluated. The adhesive leukocyte count on the endothelium was significantly lower in pretreatment group compared with control group (P < 0.01), whereas the difference was not significant in the posttreatment group. Similarly, the number of obstructed capillary was significantly lower in the pretreatment group (P < 0.01). The width of interstitium was significantly lower in the pretreatment and posttreatment group (P < 0.01 and 0.05, respectively). A comparison of white blood cell counts showed a better maintenance in pretreatment group (P < 0.05). Pretreatment of sivelestat demonstrated a protective effect on both intravascular and extravascular damage in the lung, whereas posttreatment only suppressed the latter damage.

Acute Disease↗
PubMed2006

Comparison of the protective effects of type III phosphodiesterase (PDE3) inhibitor (cilostazol) and acetylsalicylic acid on intestinal microcirculation after ischemia reperfusion injury in mice.

Antiplatelet therapy has been proposed as the treatment of choice for ischemia/reperfusion injury. The aim of this study is to elucidate the difference in effect between cilostazol (CZ) and acetylsalicylic acid (ASA) on microcirculatory disturbance in ischemia/reperfusion injury. Either 10 mg/kg of CZ (n = 14) or 100 mg/kg of ASA (n = 14) was administered orally to mice. Thereafter, 20 min of intestinal ischemia, followed by 60-min reperfusion, was applied; then, the status of submucosal microcirculation was observed under intravital microscopy. The blood cell counts and organ damage markers were examined in the portal blood. Next, 5 mm of the ileum was excised and was then histologically examined. Platelet-leukocyte aggregates were often observed in the postcapillary venules, and this formation was significantly reduced by both CZ and ASA. The number of adherent leukocytes was significantly lesser in the CZ-treated mice than in the ASA-treated mice (P < 0.01). The leukocyte number, lactate dehydrogenase, and lactate levels were best maintained in the CZ-treated mice (P < 0.05). The villus height was best preserved in the CZ-treated mice. Cilostazol inhibited not only the platelet aggregation but also the leukocyte adhesion to the endothelium, thereby inducing organ protection.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2005

Antithrombin ameliorates endotoxin-induced organ dysfunction more efficiently when combined with danaparoid sodium than with unfractionated heparin.

OBJECTIVE: This study investigated the potential benefits of combination therapy using antithrombin (AT) with danaparoid sodium (DA) compared with the use of AT with unfractionated heparin (UFH) in the treatment of sepsis. METHODS: Rats infused with lipopolysaccharide were treated with either DA alone, AT alone, AT plus DA, AT plus UFH, or human serum albumin as controls. AT (125 U/kg) was injected into the AT group immediately after lipopolysaccharide infusion. The AT/DA and AT/UFH groups received the same dose of AT in conjunction with either DA (400 U/kg) or UFH (400 U/kg). The status of the mesenteric microcirculation was examined by intra-vital microscopy and the laboratory indices of coagulation, inflammation, and organ dysfunction were measured. RESULTS: The coagulation markers were improved following the administration of DA or UFH. The decreases in the WBC counts were significantly suppressed in the AT/DA group. The elevation of IL-6 decreased in the AT, DA, and AT/DA groups (all p<0.01) but not in the AT/UFH group. The prostaglandin I2 levels were significantly elevated only in the AT/DA group (p<0.05). The WBC adhesion was significantly suppressed in the DA, AT/UFH, and AT/DA groups (p<0.05), and the RBC velocity was best maintained in the AT/DA group with no associated increase in capillary hemorrhage. The elevation of ALT and BUN significantly improved only in the AT/DA group. ONCLUSION: Organ dysfunction can thus be alleviated by even moderate doses of AT replacement when co-administered with DA.

6-Ketoprostaglandin F1 alpha↗
PubMed2005

Optimizing brain tissue contrast with EPI: a simulated annealing approach.

A new magnetization preparation and image acquisition scheme was developed to obtain high-resolution brain images with optimal tissue contrast. The pulse sequence was derived from an optimization process using simulated annealing, without prior assumptions with regard to the number of radiofrequency (RF) pulses and flip angles. The resulting scheme combined two inversion pulses with the acquisition of three images with varying contrast. The combination of the three images allowed separation of gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) based on T1, contrast. It also enabled the correction of small errors in the initial T1 estimates in postprocessing. The use of three-dimensional (3D) sensitivity-encoded (SENSE) echo-planar imaging (EPI) for image acquisition made it possible to achieve a 1.15(3) mm3 isotropic resolution within a scan time of 10 min 21 s. The cortical GM signal-to-noise ratio (SNR) in the calculated GM-only image varied between 30 and 100. The novel technique was evaluated in combination with blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) on human subjects, and provided for excellent coregistration of anatomical and functional data.

Brain Mapping↗
PubMed2005

Laparoscopy-assisted low anterior resection with a prolapsing technique for low rectal cancer.

Laparoscopy-assisted low anterior resection (LAR) for low rectal cancer is a difficult procedure, presenting problems with rectal washout, selecting the appropriate distal transection line, and achieving safe anastomosis. To resolve these problems, we used a prolapsing technique to perform laparoscopy-assisted LAR. Total mesorectal excision (TME) is performed laparoscopically. The proximal colon is transected laparoscopically with the aid of an endoscopic stapler, and the distal rectum, including the lesion, are everted and pulled transanally to outside the body. Only washout of and wiping off the distal rectum and intestinal resection are performed extracorporeally. The distal rectum is pushed back through the anus into the pelvis, and intracorporeal anastomosis is completed laparoscopically with a double-stapling technique. Our limited experience suggests that the prolapsing technique helps to prevent problems with laparoscopy-assisted LAR in selected patients with low rectal cancer.

Colectomy↗
PubMed2005

Activated protein C improves the visceral microcirculation by attenuating the leukocyte-endothelial interaction in a rat lipopolysaccharide model.

OBJECTIVE: Abnormalities in the vascular endothelial function play an important role in the development of septic organ dysfunction. The aim of the study was to examine the effect of recombinant human activated protein C on leukocyte-endothelial interaction in endotoxemia. DESIGN: Experimental animal model of sepsis. SETTING: University research laboratory. SUBJECTS: Normal Wistar rats. Each animal was infused with 4.5 mg/kg lipopolysaccharide to simulate severe sepsis. INTERVENTIONS: Rats were injected with endotoxin simultaneously with either a low or a high dose of recombinant human activated protein C (n = 7). One, 2, and 3 hrs after injection, mesenteric microcirculation was observed under intravital microscopy. In another series, tumor necrosis factor, interleukin-6, alanine transaminase, and blood urea nitrogen levels were evaluated (n = 5). MEASUREMENTS AND MAIN RESULTS: The adhesive leukocyte count on the endothelium was significantly suppressed in both high-dose and low-dose groups (p < .01 and .05, respectively). The bleeding events decreased in the low-dose treatment group compared with both the control (p < .05) and high-dose group (p < .05). Microcirculatory flow as expressed by red blood cell velocity was maintained better in the low-dose group. Comparison of cytokine levels showed a significant decrease in the treatment groups. Organ damage markers were also suppressed in the treatment groups (p < .05) CONCLUSIONS: Recombinant human activated protein C demonstrated a protective effect on microcirculation through the inhibition of leukocyte-endothelial interaction and suppression of inflammatory cytokine production.

Alanine Transaminase↗
PubMed2005

Association between the severity of sepsis and the changes in hemostatic molecular markers and vascular endothelial damage markers.

It is well known that disorders of coagulation and fibrinolysis play a major role in the development of organ dysfunction during sepsis. Furthermore, the importance of the early initiation of anticoagulation therapy for severe cases has been emphasized based on the success of recent clinical trials. The purpose of this study is to search for useful markers for predicting organ dysfunction. Plasma samples were prospectively collected from 78 patients within 48 h after the onset of sepsis. Hemostatic markers and endothelial damage markers were compared between the patients with and without organ dysfunction. The WBC and platelet counts were not different between the groups. In contrast, fibrin/fibrinogen degradation products, D-dimer, thrombin-antithrombin complex, plasmin alpha2-antiplasmin complex, soluble fibrin, and total plasminogen activator inhibitor-1 were significantly higher, and the antithrombin activity and protein C levels were lower in the patients with organ dysfunction. Thus, the changes in the hemostatic molecular markers were associated with organ dysfunction from an early stage of sepsis, and antithrombin and protein C activities were found to be the most reliable markers.

Adult↗
PubMed2004

Temporal dynamics of the BOLD fMRI impulse response.

Using computer simulations and high-resolution fMRI experiments in humans (n=6) and rats (n=8), we investigated to what extent BOLD fMRI temporal resolution is limited by dispersion in the venous vasculature. For this purpose, time-to-peak (TTP) and full-width at half-maximum (FWHM) of the BOLD impulse response (IR) function were determined. In fMRI experiments, a binary m-sequence probe method was used to obtain high-sensitivity model-free single-pixel estimates of IR. Simulations of postcapillary flow suggested that flow-related dispersion leads to a TTP and FWHM increase, which can amount to several seconds in larger pial veins. fMRI experiments showed substantial spatial variation in IR timing within human visual cortex, together with a correlation between TTP and FWHM. Averaged across the activated regions and across subjects, TTP and FWHM were 4.51+/-0.52 and 4.04+/-0.42 s, respectively. In regions of interest (ROI) weighted toward the larger venous structures, TTP and FWHM increased to 5.07+/-0.64 and 4.32+/-0.48 s, respectively. In rat somatosensory cortex, TTP and FWHM were substantially shorter than in humans (2.73+/-0.60 and 2.28+/-0.63 s, respectively). These results are consistent with a substantial macrovascular dispersive contribution to BOLD IR in humans, and furthermore suggest that neurovascular coupling is a relatively rapid process, with a resolution below 2.3 s FWHM.

Adult↗
PubMed2004

The efficacy of long-term oral chemotherapy with 5'-deoxy-5-fluorouridine and cyclophosphamide for recurrent breast cancer.

BACKGROUND: 5'-Deoxy-5-fluorouridine (5'-DFUR) is a prodrug of 5-fluorouracil (5-FU), which is known to be converted by thymidine phosphorylase (dThdPase). A recent preclinical study revealed that cyclophosphamide (CPA) upregulated dThdPase activity, specifically in tumor cells. The purpose of the present study was to examine the efficacy of long-term administration of 5'-DFUR/CPA for patients with recurrent breast cancer. METHODS: Fifteen breast cancer patients with recurrent tumors entered this study. Ten patients had bone metastasis, five had lung metastasis, and two had liver metastasis. Three patients had multiorgan metastases. All patients had had previous exposure to standard chemotherapy such as CAF (CPA, doxorubicin, and 5-FU) and CMF (CPA, methotrexate, and 5-FU). The patients were orally administered with daily doses of 5'-DFUR at 800-1200 mg and CPA at 200 mg for 2 weeks as induction therapy, followed by 2 weeks' rest (one to two cycles). Daily doses of 800 mg of 5'-DFUR and 100 mg of CPA (as maintenance therapy) were continuously administered thereafter. Ten of the 15 patients received the maintenance therapy alone. The treatment was continued for at least 24 months (average, 35.2 months). RESULTS: The main findings included a significant decrease in pain in nine patients with bone metastasis, and this effect continued for more than 2 years. As the pain decreased, the patients' quality of life (QOL) was improved. Liver metastasis was diminished in two out of two patients. Hematological toxicity of more than grade 3 was recognized in three patients, but only during the induction therapy. CONCLUSION: Oral administration of 5'-DFUR/CPA is well tolerated and useful for patients with recurrent breast cancer.

Administration, Oral↗
PubMed2004

Hunting for neuronal currents: absence of rapid MRI signal changes during visual-evoked response.

While recent reports have advocated the use of magnetic resonance imaging (MRI) to detect the effects of neuronal currents associated with human brain activity, only preliminary experimental data have been presented so far to demonstrate the feasibility of the method. Furthermore, it has not been adequately demonstrated that (1) MRI can separate neuronal current (NC) effects from other effects such as blood oxygen level-dependent (BOLD) contrast; (2) MRI has adequate sensitivity to detect NCs in vivo. In this work, we introduce a method that can separate slow (e.g., BOLD) processes from potential rapid (e.g., NC) processes and apply this method to investigate whether MRI allows detection of an NC response to a visual stimulus. MRI studies (n = 8) at 3.0 T using a sensitive multichannel detector showed insignificant effects related to NCs (averaged t < 0.05), in the presence of a highly significant BOLD signal (t = 6.15 +/- 0.90). In contrast, magnetoencephalography (MEG) experiments performed under similar conditions on the same subjects showed highly significant electrical activity (t = 7.90 +/- 2.28). It is concluded that, under the conditions used in this study, the sensitivity of MRI to detect evoked responses through NCs is at least an order of magnitude below that of BOLD-based functional MRI (fMRI) or MEG and too low to be practically useful.

Data Interpretation, Statistical↗
PubMed2004

Functional imaging of gustatory perception and imagery: "top-down" processing of gustatory signals.

By recalling gustatory memories, it is possible to generate vivid gustatory perceptions in the absence of gustatory inputs. This gustatory image influences our gustatory processing. However, the mechanism of the "top-down" modulation of gustatory perception in the human is still unclear. Our findings propose a new perspective on the neural basis of gustatory processing. Although gustatory imagery and gustatory perception shared common parts of neural substrates, there was an asymmetrical topography of activation in the insula: the left insula was predominantly activated by gustatory imagery tasks. In addition, the middle and superior frontal gyri were not activated by gustatory perception but they participated in the generation of gustatory hallucinations. These regions in the frontal cortex may mediate the "top-down" control of retrieving gustatory information from the storage of long-term memories.

Adult↗
PubMed2004

Laparoscopic surgery for left paraduodenal hernia.

Paraduodenal hernia is a rare condition but the most common internal hernia. We describe the case of a 51-year-old man who was admitted with a complaint of 2 months' duration of recurrent left lower abdominal pain. Left paraduodenal hernia complicated by bowel malrotation was diagnosed, and the patient underwent laparoscopic surgery since no bowel necrosis was observed. The bowel incarcerated in the hernial sac was reduced, and an Endostitch was used to close the hernial orifice with continuous sutures. The postoperative course was good, and the patient was discharged 7 days after surgery. For paraduodenal hernia without bowel necrosis, particularly a left hernia, reduction of the incarcerated bowel and closure of the hernial orifice are relatively easy in terms of technique, and laparoscopic surgery may be the surgical method of choice because of its minimal invasiveness and aesthetic advantage.

Duodenal Diseases↗
PubMed2003

Interindividual and interspecies variations of the extrastriate visual cortex.

Functional homology between human and macaque visual cortices has provided an important cue to functional subdivisions of the human visual cortex, but it is unclear beyond V1. We estimated the sizes and the visual field eccentricity functions of the extrastriate visual areas of human brains using MRI and fMRI measurements to analyze the interindividual and interspecies variations. We found distinctive features of the area fraction values relative to V1 and the visual field eccentricity functions beyond V2 between the human and the macaque visual cortices. This suggests that selection on color-form and stereoscopic vision, associated with processing and manipulating socio-visual stimuli, may generate variations of the architecture of the extrastriate visual cortex beyond V2.

Adult↗