Biomedical subjects

Toshio Moritani

Publications and source records attributed to Toshio Moritani.

49 records · Page 3Linked to original sources

PubMed2002

Vasospasm model of a rabbit common carotid artery for endovascular research.

RATIONALE AND OBJECTIVES: Endovascular treatments such as balloon angioplasty and injection of vasodilators play an important role in cerebral vasospasm refractory to first-line therapies. Experimental studies with intracranial arteries of animals have some limitations, however, because in most cases endovascular devices are too large and inflexible to catheterize these arteries. The purpose of this study was to document the natural course of a vasospasm model using a rabbit common carotid artery. MATERIALS AND METHODS: The common carotid arteries of 24 New Zealand white rabbits were used. Autologous blood was placed around the isolated artery and kept in place with a silicone cuff. The time course of vasoconstriction after blood clot placement was examined with angiography and with histopathologic evaluation. RESULTS: Angiographic vasoconstriction was prominent on day 2, less obvious on day 9, and absent on day 30. At histopathologic evaluation, folding of the endothelial surface, corrugation of the internal elastic lamina, and thickening of the arterial wall were observed in the group with blood clot placements around the artery on day 2 and were nearly absent on day 30. CONCLUSION: This model may be used for the study of endovascular treatments of vasospasm.

Animals↗

PubMed2002

Cardiac autonomic nervous activities and cardiorespiratory fitness in older men.

BACKGROUND: Aging associated changes in sympatho-vagal activities have been widely studied. However, little is known about the association between cardiorespiratory fitness level and cardiac autonomic nervous activities in conjunction with baroreflex sensitivity in healthy older men. METHODS: We performed an incremental submaximal exercise test in 24 healthy, older men aged 60-70 years. They were divided into physically fit (PF, oxygen uptake at anaerobic threshold [ATO(2)] = 25.2 +/- 0.85 ml.kg(-1).min(-1)) and physically unfit (PU, ATO(2) = 19.6 +/- 0.42 ml.kg(-1).min(-1)) groups, based upon the results of an incremental exercise stress test. The cardiac autonomic nervous system (ANS) activities were assessed by means of power spectral analysis of heart rate variability. Baroreflex sensitivity (BRS) testing was performed using simultaneous beat-by-beat blood pressure and heart rate measurement during a transition from supine horizontal position to 60 degrees head-up-tilting (HUT). RESULTS: At rest conditions, the high-frequency component ( p =.03) and total power ( p =.04) of heart rate variability spectrum were significantly higher in the PF group. The BRS assessed during passive HUT was also significantly higher (7.5 +/- 0.5 vs 3.0 +/- 0.4 ms.mm Hg(-1), p =.001) in the PF compared with the PU group. In addition, a significant correlation coefficient (r =.73, p =.001) was found between ATO(2) and BRS among the subjects. CONCLUSIONS: The maintenance of high cardiorespiratory function, i.e., higher ATO(2) through a life-long active lifestyle including endurance exercise, may play an important role in reserving cardiac ANS and BRS in older men.

Aged↗

PubMed2002

Changes in blood volume and oxygenation level in a working muscle during a crank cycle.

PURPOSE: This study examined circulatory and metabolic changes in a working muscle during a crank cycle in a pedaling exercise with near-infrared spectroscopy (NIRS). METHODS: NIRS measurements sampled under stable metabolic and cadence conditions during incremental pedaling exercise were reordered according to the crank angles whose signals were obtained in eight male subjects. RESULTS: The reordered changes in muscle blood volume during a crank cycle demonstrated a pattern change that corresponded to changes in pedal force and electrical muscle activity for pedal thrust. The top and bottom peaks for muscle blood volume change at work intensities of 180 W and 220 W always preceded (88 +/- 32 and 92 +/- 23 ms, respectively) those for muscle oxygenation changes. Significant differences in the level of NIRS parameters (muscle blood volume and oxygenation level) among work intensities were noted with a common shape in curve changes related to pedal force. In addition, a temporary increase in muscle blood volume following a pedal thrust was detected at work intensities higher than moderate. This temporary increase in muscle blood volume might reflect muscle blood flow restriction caused by pedal thrusts. CONCLUSION: The results suggest that circulatory and metabolic conditions of a working muscle can be easily affected during pedaling exercise by work intensity. The present method, reordering of NIRS parameters against crank angle, serves as a useful measure in providing additional findings of circulatory dynamics and metabolic changes in a working muscle during pedaling exercise.

Adult↗

PubMed2002

Effect of cycling experience and pedal cadence on the near-infrared spectroscopy parameters.

PURPOSE: Previously we demonstrated that the method to reorder near-infrared spectroscopy (NIRS) parameters against crank angle could serve as a useful measure in providing circulatory dynamics and metabolic changes in a working muscle during pedaling exercise. To examine further applicability of this method, we investigated the effects of cycling experience and pedal cadence on the NIRS parameters. METHODS: Noncyclists (NON), triathletes (TRI), and cyclists (CYC) performed pedaling exercises at a work intensity of 75% VO2max while changing pedal cadence (50, 75, 85, and 95 rpm). Physiological and biomechanical responses and NIRS parameters were measured. RESULTS: NIRS measurements determined with the reordered NIRS change demonstrated significant differences depending on the factors. The bottom peak of reordered NIRS changes in muscle blood volume and oxygenation level shifted upward with an increase in pedal cadence in NON but remained unchanged in CYC. The reordered NIRS change demonstrated a temporary increase at the crank angle corresponding to the relaxation phase of the working muscle. This temporary increase was observed even in the highest pedal cadence in CYC. The difference in levels between the peak of the temporary increase and the bottom peak of reordered NIRS change (LPB-diff) for CYC at 85 rpm was significantly larger than that for NON. The results with NIRS parameters corresponded to changes in pedal force and myoelectric activity during pedal thrust. CONCLUSIONS: The bottom peak level of the reordered NIRS changes and LPB-diff determined for blood volume are available to detect noninvasively the differences in circulatory dynamics and metabolic change during pedaling exercises performed at different pedal cadences and also to estimate the difference of physiological and technical developments for endurance cycling in athletes.

Adaptation, Physiological↗

PubMed2002

Characteristics of surface mechanomyogram are dependent on development of fusion of motor units in humans.

The purpose of this study was to test whether surface mechanomyogram (MMG) recorded on the skin reflects the contractile properties of individual motor units in humans. Eight motor units in the medial gastrocnemius muscle were identified, and trains of stimulation at 5, 10, 15, and 20 Hz were delivered to each isolated motor unit. There was a significant positive correlation between the duration of MMG and twitch duration. MMG amplitude decreased with increasing stimulation frequency. Reductions in MMG amplitude were in parallel with the reductions in force fluctuations, and the rate of change in both was positively correlated across the motor units. Rate of change in MMG amplitude against force was negatively correlated to half relaxation time and twitch duration. Similar negative correlations were found between force fluctuations and contractile properties. These results provide evidence supporting a direct relation between MMG and contractile properties of individual motor units within the gastrocnemius muscle, indicating that surface MMG is dependent on the contractile properties of the activated motor units in humans.

Adult↗

PubMedDate not supplied

Potential association between endogenous leptin and sympatho-vagal activities in young obese Japanese women.

Leptin is an adipocyte-derived hormone that decreases food intake and increases energy expenditure through the activation of the sympathetic nervous system (SNS). Notwithstanding recent intensive research, the underlying physiological mechanism of leptin as well as the etiology of obesity in humans remains elusive. The present study attempted to investigate the potential association between endogenous circulating leptin and sympatho-vagal activities in age- and height-matched obese and nonobese healthy young women. Plasma leptin concentrations were measured by radioimmunoassay. The autonomic nervous system activity was assessed during the resting condition by means of a recently devised power spectral analysis of heart rate variability, which serves to identify three separate frequency components, very low (VLO), low (LO), and high (HI). Plasma leptin concentrations were greater in the obese than in the control group (45.7 +/- 5.89 vs. 11.2 +/- 1.10 ng. ml(-1), P < 0.01). As to the contribution of endogenous leptin to SNS activity, both the ratios of the VLO frequency component reflecting thermoregulatory sympathetic function and the global SNS index [(VLO + LO)/HI] to plasma leptin concentration were markedly reduced in the obese compared to the control group (VLO per leptin: 5.9 +/- 1.39 vs. 37.8 +/- 8.1 ms(2). ml. ng(-1), P < 0.01; SNS index per leptin: 0.04 +/- 0.008 vs. 0.33 +/- 0.01 ml c. ng(-1), P < 0.01). Additionally, a nonlinear regression analysis revealed that these ratios exponentially decreased as a function of body fat content (VLO per leptin r(2) = 0.57, P < 0.01; SNS index per leptin r(2) = 0.53, P < 0.01). Our data suggest that reduced sympathetic responsiveness to endogenous leptin production, implying peripheral leptin resistance, might be a pathophysiological feature of obesity in otherwise healthy young women. The findings regarding the association of leptin, body fat content, and SNS activity further indicate that the 30% of total body fat, which has been used as a criterion of obesity, might be a critical point at which leptin resistance is induced.

Body Composition↗

PubMedDate not supplied

Magnetic resonance imaging of prostate carcinoma using phased-array coils: therapeutic effect and recurrence.

Magnetic resonance imaging with phased-array coils was performed in patients with prostate carcinoma before and after hormonal therapy, radiation therapy or radical prostatectomy to evaluate therapeutic effect and recurrence. After hormonal therapy, the prostate gland, seminal vesicle and primary site of tumor usually decrease in size with variable T2 hypointensity. Recurrent or residual tumors after hormonal therapy usually represent T2 hyperintense lesions compared to the hypointensity of the surrounding tissues. Changes of metastatic sites after therapy were also demonstrated.

Androgen Antagonists↗

PubMedDate not supplied

Magnetic resonance venography of achondroplasia: correlation of venous narrowing at the jugular foramen with hydrocephalus.

In achondroplasia, venous narrowing associated with a small skull base leads to elevated venous pressure which impairs cerebrospinal fluid (CSF) absorption, resulting in communicating hydrocephalus. We correlated venous narrowing at the jugular foramina and collateral circulation on magnetic resonance venography (MRV) with ventricular size in 17 patients. Patients were divided into three groups: Group I: progressive hydrocephalus; Group II: nonprogressive hydrocephalus; and Group III: normal ventricular size. The grades of venous narrowing and types of collaterals were well correlated with hydrocephalus groups.

Achondroplasia↗

PubMedDate not supplied

Diffusion-weighted MR imaging of posterior reversible leukoencephalopathy syndrome: a pictorial essay.

Posterior reversible leukoencephalopathy syndrome is characterized by reversible white matter lesions. However, ischemic injury with irreversible damage may occur. This pictorial essay illustrates MR features associated with posterior reversible leukoencephalopathy syndrome. We will emphasize the role of diffusion-weighted imaging for the discrimination of irreversible ischemic injury from reversible vasogenic edema.

Adult↗

PubMedDate not supplied

Sickle cell cerebrovascular disease: usual and unusual findings on MR imaging and MR angiography.

This paper demonstrates usual and unusual findings on MR imaging (MRI) including fluid-attenuated inversion recovery (FLAIR), diffusion- and perfusion-weighted image and MR angiography (MRA) in 30 patients with sickle cell cerebrovascular disease. This paper also illustrates the underlying pathophysiology of sickle cell cerebrovascular disease by using the cases with usual and unusual MR findings, including long-time follow-up cases during transfusion therapy. MRI and MRA are useful in defining the basis for stroke and assessing the effects of chronic transfusion therapy.

Adolescent↗

PubMedDate not supplied

CNS vasculitis and vasculopathy: efficacy and usefulness of diffusion-weighted echoplanar MR imaging.

This pictorial essay illustrates the usefulness of diffusion-weighted imaging (DWI) on various vasculitis or vasculopathies, including systemic lupus erythematosus (SLE), Behçet's disease, Churg-Strauss disease, primary angitis of the central nervous system (PACNS), giant cell arteritis, infectious vasculitis, sickle cell disease, drug-induced vasculopathy and hypertensive vasculopathy. DWI proves to detect small and active ischemic changes not visible on conventional MRI, and it clearly discriminates cytotoxic from vasogenic edema in patients with cerebral vasculitis or vasculopathy. DWI seems useful in assessing the treatment and patient outcome.

Adult↗

PubMedDate not supplied

Epidermal nevus syndrome: megalencephaly with bihemispheric and cerebellar involvement: imaging and neuropathologic correlation.

Epidermal nevus syndrome (ENS) is a sporadic neurocutaneous disorder characterized by the combination of epidermal nevi with significant central nervous system, eye, and skeletal abnormalities. Hemimegalencephaly and related brain abnormalities are the dominant neuropathologic abnormalities in ENS. Magnetic resonance imaging features of the case reported here revealed enlargement of both cerebral hemispheres and malformed basal ganglia, with incomplete separation of the caudate nucleus and putamen. In addition, the right cerebellar hemisphere was enlarged, with disorganized folia. None of these findings have been reported previously in this disorder.

Basal Cell Nevus Syndrome↗

PubMedDate not supplied

Proton magnetic resonance spectroscopy and diffusion-weighted imaging of central nervous system whipple disease.

A 72-year-old man presented with a 6-month history of dysphagia, fatigue, 60-lb weight loss, and central nervous system (CNS) deficits. Diffusion-weighted magnetic resonance imaging (MRI) of the brain showed mildly elevated nonrestricted apparent diffusion coefficients in the middle cerebellar peduncles, and magnetic resonance spectroscopy (MRS) showed decreased N-acetylaspartate and creatine with increased choline. Diffusion-weighted MRI and MRS offer noninvasive methods to help evaluate in vivo physiologic changes of CNS involvement in Whipple disease.

Aged↗