Biomedical subjects

S Endo

Publications and source records attributed to S Endo.

At least 217 records · Page 12Linked to original sources

PubMed1998

Development of a flow estimation and control system of an implantable centrifugal blood pump for circulatory assist.

A bypass flow rate estimation and control system (BECS) for an implantable centrifugal blood pump (ICBP) has been developed in our institute. The estimated flow rate (EF) of the ICBP was derived from the electric power consumption, the rotating speed of a motor, and the blood viscosity presumed by the hematocrit and body temperature. The error in the EF was 0.5 +/- 0.4 L/min in in vivo experiments for 40 days. The rotating speed of the motor was controlled automatically every 200 ms to bring the EF in accord with the desired flow rate (DF). The reactivity and accuracy of the BECS were investigated in in vitro and in vivo experiments. The ICBP was operated by the BECS in a mock circuit in parallel with a pulsatile ventricular assist device (PVAD) to simulate left heart bypass. The reactivity was evaluated by changing the DF from 7 L/min to 5 L/min at an afterload of 160/97 mm Hg. To evaluate the accuracy of the BECS, the ICBP was driven under the aortic pressure of 110/85 mm Hg in the abdominal wall of an adult goat (70 kg). The DF was set at 5 L/min for 4 min for the goat in an awake condition. It took 13 s to change the flow rate in the in vitro experiment. The measured flow rate (MF) was maintained at 5.0 +/- 0.2 L/min by the BECS in vivo. In conclusion, the BECS has moderate reactivity and accuracy.

Abdominal Muscles↗

PubMed1998

Intrathoracic and intraabdominal wall implantation of a centrifugal blood pump for circulatory assist.

An implantable centrifugal pump (ICP) 320 ml in volume and 830 g in weight has been developed for prolonged circulatory assist. The antithrombogenicity of the ICP is provided by a balancing hole in the center of the impeller. The watertightness and histocompatibility of the ICP are supported by its silicone ring seal and its casing of titanium and acrylic resin, respectively. The total efficiency of the ICP was 30% at a 5 L/min flow rate and a 100 mm Hg head. The heat generation, watertightness, and anatomical fitting of the ICP were assessed in an intrathoracic implantation in a goat (66 kg) and in an intraabdominal wall implantation in a goat (70 kg). Warfarin was given for anticoagulation in each experiment to keep the prothrombin time around 1.7 times that of the control. The temperatures of the pump surface, the pleura, and the room were measured every 3 h. Anatomical fitting was evaluated by pathological observation after the termination of the experiment. The ICP could run for 40 days in the chest cavity and for 11 days in the abdominal wall. The temperature of the motor remained about 1.8 degrees C higher than the reference in both experiments. The ICP was completely covered by a layer of smooth fibrous tissue. The moisture content of the seals remained normal. Although a small amount of atelectasis was found in the lingula, neither lung adhesion nor necrotic change of the chest wall was observed. The inflammation of the surrounding tissue including foreign body reaction and thermal burn was minimal. In conclusion, the ICP has satisfied in vivo testing of its watertightness, exothermicity, and anatomical fitting.

Abdominal Muscles↗

PubMed1998

Prolonged nonpulsatile left heart bypass with reduced systemic pulse pressure causes morphological changes in the aortic wall.

We investigated the morphological changes in the aorta due to reduced systemic pulse pressure in prolonged nonpulsatile left heart bypass (LHB). Nineteen adult goats were divided into 3 groups, the nonpulsatile group in which nonpulsatile LHB was conducted, the pulsatile group in which pulsatile LHB was conducted, and the control group used as the normal control. The average aortic pulse pressures were 12, 47, and 37 mm Hg, respectively. The descending aorta was subjected to morphological examination. In the nonpulsatile group, the wall was significantly thinner, and the volume ratio of smooth muscle cells (SMCs) was much lower. In terms of the SMC type classification, the proportion of SMCs with low activity and low contractility was higher, and the cell density of the SMCs was increased compared to those in the other groups. These results indicate that prolonged nonpulsatile LHB causes morphological atrophic changes in the aorta.

Animals↗

PubMed1998

Development of design methods of a centrifugal blood pump with in vitro tests, flow visualization, and computational fluid dynamics: results in hemolysis tests.

There are few established engineering guidelines aimed at reducing hemolysis for the design of centrifugal blood pumps. In this study, a fluid dynamic approach was applied to investigate hemolysis in centrifugal pumps. Three different strategies were integrated to examine the relationship between hemolysis and flow patterns. Hemolytic performances were evaluated in in vitro tests and compared with the flow patterns analyzed by flow visualization and computational fluid dynamic (CFD). Then our group tried to establish engineering guidelines to reduce hemolysis in the development of centrifugal blood pumps. The commercially available Nikkiso centrifugal blood pump (HPM-15) was used as a standard, and the dimensions of 2 types of gaps between the impeller and the casing, the axial and the radial gap, were varied. Four impellers with different vane outlet angles were also prepared and tested. Representative results of the hemolysis tests were as follows: The axial gaps of 0.5, 1.0, and 1.5 mm resulted in normalized index of hemolysis (NIH) values of 0.0028, 0.0013 and 0.0008 g/100 L, respectively. The radial gaps of 0.5 and 1.5 mm resulted in NIH values of 0.0012 and 0.0008 g/100 L, respectively. The backward type vane and the standard one resulted in NIH values of 0.0013 and 0.0002 g/100 L, respectively. These results revealed that small gaps led to more hemolysis and that the backward type vane caused more hemolysis. Therefore, the design parameters of centrifugal blood pumps could affect their hemolytic performances. In flow visualization tests, vortices around the impeller outer tip and tongue region were observed, and their patterns varied with the dimensions of the gaps. CFD analysis also predicted high shear stress consistent with the results of the hemolysis tests. Further investigation of the regional flow patterns is needed to discuss the cause of the hemolysis in centrifugal blood pumps.

Animals↗

PubMed1998

Neuronavigation using an articulated arm with a bayonet probe on a computer graphic composite of magnetic resonance and computerized tomography images.

This report describes a neurosurgical navigational system using a newly-designed articulated arm with an interchangeable probe shaped like a bayonet, which can be used in deep structures through narrow openings. This system enables three-dimensional integration of magnetic resonance and computed tomographical images, and thereby yields computer graphic composites of the scalp, brain, skull, and vessels. The arm was used in 15 patients during open brain surgery, including 5 skull base procedures. This system was useful for comprehension of skull base anatomy and could conveniently be used in microscopic neurosurgical procedures without limiting the operative field.

Adult↗

PubMed1998

Developmental malformations and intrauterine deaths in gamma-ray-irradiated scid mouse embryos.

PURPOSE: To examine the induction by radiation of developmental malformations and intrauterine deaths in severe combined immunodeficiency (scid) mice. MATERIALS AND METHODS: The scid embryos, as well as those of C.B-17 control mice, were irradiated with graded doses of 60Co gamma-rays on gestation day 8. RESULTS: Intrauterine deaths in scid mice increased with radiation dose, and their frequency was substantially higher than in C.B-17 mice. The LD50 for intrauterine death in scid mice was 0.58 Gy and 1.25 Gy in C.B-17 mice. In addition, after irradiation scid mice showed several types of developmental malformations, including meningoencephalocele, spina bifida, eye defects, tail defects and oedema. Malformation incidences were higher in scid than in C.B-17 mice: 33.3% in scid mice irradiated with 0.75 Gy and 13.0% in C.B-17 mice irradiated with 1.0 Gy. However, when malformation incidences were plotted against intrauterine deaths, all the data, irrespective of the type of mouse, essentially fell along a single straight line. CONCLUSIONS: These results suggest that some mechanism common to both scid and normal mice induces developmental malformations. This mechanism involves cell killing. Residual DNA damage, such as double-strand breaks, could be associated with radiation-induced teratogenesis.

Abnormalities, Radiation-Induced↗

PubMed1998

Monte Carlo simulation of in vivo measurements of 90Sr + 90Y bremsstrahlung.

The purpose of this study was to calculate the 90Sr + 90Y bremsstrahlung yield generated in bone quantitatively, and to determine the optimum conditions required for in vivo measurements of the yield, assuming that a given amount of contamination, due to the ordinary activities of 137Cs and 40K, is present within the human body. Several approximations in the distribution of activities in various body phantoms, simulating the human leg, waist and head, were made for simplicity. All the calculations were carried out using an in-house Monte Carlo code. The photon spectra incident on a detector window, of diameter 200 mm, positioned 1 mm from the surface of each phantom were obtained. A pseudo-peak of 90Sr + 90Y bremsstrahlung was observed at approximately 50 keV with a full width at half maximum of 60 keV (FWHM). The signal-to-background ratio, eta, where eta represents the ratio of the number of photons in the energy interval between 30 to 160 keV in the bremsstrahlung spectrum produced by 1 Bq kg(-1) of 90Sr and the background spectrum, which is assumed to comprise of 1 Bq kg(-1) of 137Cs and 60 Bq kg(-1) of 40K, was evaluated in order to determine the optimum measuring conditions. An optimum eta value of 0.0353 was obtained for the leg phantom, of bone diameter 30 mm, covered by a 1 mm layer of soft tissue. Combining the present calculations with the conventional measurements, a new and simpler method for evaluating the body burden activity of a beta emitter, such as 90Sr, is proposed.

Beta Particles↗

PubMed1998

Residual 60Co activity in steel samples exposed to the Hiroshima atomic-bomb neutrons.

Residual 60Co radioactivity produced by the neutrons from the Hiroshima atomic bomb has been measured by means of gamma-ray spectrometry for seven steel samples located up to 1,800 m slant range and one control sample obtained at 4.5 km from the hypocenter. After removing the main constituent of iron ions from the steel sample by the solvent extraction method, nickel and cobalt were chemically separated by the ion exchange process. Gamma-ray measurements were performed with a low background well-type germanium detector. Derived specific activities 60Co:Co were compared with previous measurements and with the calculation based on the neutron fluence of current dosimetry system DS86. It has been shown that a systematic discrepancy exists between the measured and calculated activity. The calculated-to-measured ratios for 60Co are consistent with those of 152Eu and 36Cl activity.

Chlorine↗

PubMed1998

Early potentials of direct cortical responses: experimental study in dogs and pathophysiological and clinical implications.

OBJECTIVE: The characteristics of the early component of the direct cortical response have not been well studied, although direct cortical response recording is a common method of brain function monitoring. METHODS: In this experimental study, we sought conditions affording the clearest recording of the early potential, by varying the polarity and low-cutoff filter setting, and we confirmed that the early potential consists of two components, P1 and P2. RESULTS: When subcortical damage was induced by local cerebral compression or saline injection, transient changes in P1 and permanent disappearance of P2 were observed. P2 also disappeared when the fiber connections between the cortex and the basal ganglia, including the thalamus, were destroyed by wire insertion. With deep recording, both P1 and P2 exhibited potential reversal at a level histologically confirmed to be in Layer V of the cortex. CONCLUSION: These findings suggest that P1 is a spike reflecting the activity of pyramidal cells evoked by electrical stimulation of the brain surface and that P2 is a potential arising in Layer V of the cortex and is related to afferent fibers from the thalamus. Recording of P2 may be useful for monitoring for subcortical damage.

Animals↗

PubMed1998

Proton magnetic resonance spectroscopy of the brain in three cases of Rett syndrome: comparison with autism and normal controls.

Rett syndrome (RS) is a clinically defined disorder characterized by autistic behavior, and cognitive and motor skill loss early in life. We performed 1H-MRS of the brain in 3 cases of RS in comparison with in autism and controls. The older patient with RS demonstrated decreased N-acetylaspartate (NAA)/choline (Cho) and NAA/creatine (Cr) ratios when compared with the autism and control groups, whereas the younger patients did not demonstrate these decreased metabolite ratios. The Cho/Cr ratio did not differ among Rett syndrome, autism and controls. Since the clinical stage did not differ among the 3 cases of RS, it was suggested that NAA was decreased with increasing age and was not related with the clinical stage of RS. The NAA/Cho, NAA/Cr and Cho/Cr ratios did not differ between autism and controls. The present data suggest that there may be a secondary degenerative process of late onset in RS, which pathophysiologically differs from autism.

Adolescent↗

PubMed1998

Intracerebral temperature in patients with hydrocephalus of varying aetiology.

Brain temperature was measured at various depths beneath the pial surface in patients with hydrocephalus of varying aetiology. Temperature increased gradually with depth in all patients, with the highest temperature found in the ventricle. The difference between intraventricular and rectal temperatures (delta v-r) was greater in patients who underwent continuous ventricular drainage than in patients who underwent ventriculoperitoneal shunt (continuous ventricular drainage; 1.2 (SD 0.40) degrees C, mean (SD), n=5 v ventriculoperitoneal shunt; 0.4 (SD 0.45) degrees C, n=16; p< 0.05). The difference between intracerebral and rectal temperatures (delta b2-r) was also greater in patients with continuous ventricular drainage than in patients with ventriculoperitoneal shunt (continuous ventricular drainage; 0.1 (SD 0.86) degrees C, n=5 v ventriculoperitoneal shunt; -0.7 (0.86) degrees C, n=16; p< 0.05). Among patients with normal pressure hydrocephalus, these differences were greater in the patients with better outcomes after shunt surgery than in the less improved group (delta v-r; 0.7 (SD 0.27) degrees C, n=7 v 0.1 (SD 0.40) degrees C, n=5, p< 0.01, delta b2-r; -0.2 (SD 0.61) degrees C, n=7 v -1.4 (0.90) degrees C, n=5, p< 0.01).

Adult↗

PubMed1998

Intracranial germinoma associated with Down's syndrome. Report of 2 cases.

It is well known that Down's syndrome is sometimes associated with leukemia. However, there have been only a few case reports of a relationship between Down's syndrome and brain tumors. We report 2 cases with histological diagnoses of germinoma. The 1st case was a 10-year-old boy with Down's syndrome complaining of seizure and left hemiparesis. Computed tomographic (CT) scan and magnetic resonance imaging (MRI) showed a mass lesion in the right basal ganglia and thalamus. Histological examination indicated two cell pattern germinomas. The 2nd case was a 20-year-old man with Down's syndrome complaining of headache and vomiting. CT scan and MRI showed a pineal region tumor with marked hydrocephalus. Surgical specimens showed typical germinoma. Only 13 cases of brain tumors associated with Down's syndrome have been reported. A higher incidence of germ cell tumors seems to be related to chromosomal abnormalities.

Adult↗

PubMed1998

Anticardiolipin antibody aggravates cerebral vasospasm after subarachnoid hemorrhage in rabbits.

BACKGROUND AND PURPOSE: We previously reported that patients with antiphospholipid antibodies (aPLs) frequently demonstrate cerebral infarction due to cerebral vasospasm after subarachnoid hemorrhage (SAH). To examine the participation of aPLs in the pathogenesis of vasospasm after SAH, we studied the relationships of aPLs and SAH in an animal model. METHODS: SAH was produced in 34 rabbits that received two subarachnoid injections of autologous arterial blood. The animals were divided into four experimental groups: SAH was induced in group A (n=9), intracutaneous injection of cardiolipin (CL) was performed before the induction of SAH in group B (n=5), intravenous injection of CL was performed before SAH in group C (n=12), and cyclosporin A was infused intravenously after the intravenous injection of CL and induction of SAH in group D (n=8). Enzyme-linked immunosorbent assay identifying the titer of IgG CL antibodies, neurological evaluation, cerebral angiography, and histological examination were performed in all four groups. RESULTS: A significant elevation of anti-CL antibodies, aggravation of neurological deficit, and reduction of caliber of the basilar artery were observed in rabbits that received the intravenous immunization of CL (group C). The administration of cyclosporin A reduced the titer of anti-CL antibody, aggravation of neurological deficit, constriction of basilar artery, and the incidence of cerebral infarction (group D). CONCLUSIONS: Anti-CL antibodies may therefore be involved in the deterioration of cerebral vasospasm after SAH.

Animals↗

PubMed1998

Estimation of dose absorbed fraction for 131I-beta rays in rat thyroid.

The dose absorbed fraction of rat thyroid by internal deposit of 131I has been calculated as a function of effective diameter of thyroid. The calculations were done using two types of Monte Carlo simulations: one was by a simple energy-loss calculation in spherical volume according to the electron stopping power, and another by a more realistic simulation using Monte Carlo N-Particle Transport code system Version 4A (MCNP). These two calculations were consistent with each other within a deviation of 5%. The absorbed fractions in spherical thyroid were drastically changed up to 5 mm diameter, and then almost all energy was deposited within 10 mm diameter. For the practical application to the animal experiment, the absorbed fractions of ellipsoid-shaped thyroids were also calculated for 1-, 4- and 9-week-old rats, where the fractions were estimated to be 0.61, 0.67 and 0.68, respectively. It was also found that the absorbed fraction of the ellipsoid with various dimensions can be simulated by a calculation for spherical volume with a comparable effective diameter.

Animals↗

PubMed1998

Hypoglossal nerve paresis caused by spontaneous dissection of kinked internal carotid artery--case report.

A 54-year-old male presented with pure hypoglossal nerve paresis. Angiography and magnetic resonance (MR) imaging showed the characteristic findings of left internal carotid artery (ICA) dissection. He received aspirin and his symptoms gradually disappeared. Repeat angiography and MR imaging showed that the lesion had completely disappeared. This case supports the hypothesis that hypoglossal nerve paresis is due to nerve stretching and compression by intramural hematoma of the dissected ipsilateral ICA, and severe tortuosity of the ICA may be a related phenomenon.

Aortic Dissection↗

PubMed1998

Pseudo-cerebrospinal fluid rhinorrhea after skull base surgery.

A 41-year-old female underwent complete resection of a left petroclival meningioma via an anterior transpetrosal approach, during which the greater superficial petrosal nerve was divided. On the 14th day after the operation, she first noticed leakage of clear fluid from her right nostril whenever the ambient room temperature rose. This pseudo-cerebrospinal fluid rhinorrhea may have developed because of parasympathetic hypersensitivity due to division of the greater superficial petrosal nerve.

Adult↗

PubMed1998

Nontraumatic convexity intradiploic arachnoid cyst.

A 63-year-old male presented with an unusual case of nontraumatic intradiploic arachnoid cyst in the frontotemporal convexity area. Skull radiography showed a circular osteolytic lesion of the right parietal bone. Computed tomography revealed a defect of the inner table, widened diploic space, and thinned outer table. Magnetic resonance imaging showed a cyst containing cerebrospinal fluid. Bone scintigraphy showed no abnormal uptakes. Intraoperative observation confirmed the neuroimaging findings. Histological examination found no abnormal findings in specimens of skull bone or arachnoid membrane. Intradiploic arachnoid cyst is characterized by parasagittal, multiple, well-demarcated osteolytic lesions on radiographs in the elderly. However, the clinical features of this disease remain unclear and diagnosis without an exploratory surgical procedure may not be possible.

Arachnoid↗

PubMed1998

Is propranolol effective in primary polydipsia?

OBJECTIVE: Psychiatric patients presenting with polydipsia are often difficult to treat with standard psychiatric interventions. Pharmacological intervention was attempted in these patients based on the hypothesis that angiotensin II, a potent dipsinogen, may be involved in the drinking behavior of patients with polydipsia. Beta-blockers inhibit renin release (and thus indirectly angiotensin II) by blocking beta receptors in the kidney. METHODS: Three patients were identified as excessive water drinkers during their hospital admissions. All three patients were eunatremic but polydipsic at the time of study. Two of the three had histories of hyponatremia and required emergency medical treatment on more than one occasion. No patients had been controlled by strict fluid restriction. Trials of propranolol were initiated to control their water drinking. RESULTS: After starting propranolol, two patients responded quickly. In one patient, fluid intake decreased from 2650 +/- 647 to 1577 +/- 361, p < .001. In the other, fluid intake decreased from over 7000 ml before starting propranolol to around 3000 ml. The mean noon body weight of the third patient, in whom it was not possible to document fluid intake or urine volume before and after administering beta-blocker, was 72.6 +/- 2.6 Kg and 66.0 +/- 1.0 Kg, respectively (p < .0001). CONCLUSIONS: These results suggest that propranolol may be useful for the treatment of polydipsia in patients with schizophrenia. Its efficacy could be related to inhibition of the renin-angiotensin system. Additional research using the controlled pharmacotherapeutic trials is required to confirm these findings.

Adrenergic beta-Antagonists↗