Biomedical subjects

M Hirata

Publications and source records attributed to M Hirata.

At least 181 records · Page 10Linked to original sources

PubMed1998

Metastatic meningeal hemangiopericytoma of thoracic spine.

We report a case of metastatic meningeal hemangiopericytoma in thoracic spine. A 49-year-old female having a history of tentorial hemangiopericytoma first found 116 months before was admitted to our hospital with acute onset of paraplegia. Magnetic resonance image revealed a tumor invading the left lamina and pedicle of the 8th thoracic vertebra, and compressing the dural sac severely. After subtotal removal of the tumor, the patient showed rapid neurological improvement. The histological findings were characteristic of hemangiopericytoma. Because extradural metastases of meningeal hemangiopericytoma occur long after previous treatment in unexpected sites especially in skeletal system, repeated bone scintigraphy is essential.

Adult↗

PubMed1998

Tolerogenic activity of polyethylene glycol-conjugated lysozyme distinct from that of the native counterpart.

Conjugation of proteins with polyethylene glycol (PEG) has been reported to make the proteins tolerogenic. Native proteins are also potentially tolerogenic when given without adjuvants. We compared immunotolerogenic activities between PEG-conjugated and native hen egg-white lysozyme (HEL). BALB/c mice were given consecutive weekly intraperitoneal administrations of PEG-conjugated HEL, unmodified HEL or phosphate-buffered saline (PBS), for 3 weeks, then challenged with HEL in Freund's complete adjuvant. The pretreatment with PEG-HEL tolerized both T-cell and humoral responses, while native HEL tolerized only the T-cell response. Immunoglobulin G1 (IgG1) antibody was already elevated in HEL-pretreated mice prior to challenge immunization, followed by suppressed IgG2a and IgG2b, but spared IgG1 production after the antigen challenge, whereas PEG-HEL-pretreated mice produced no antibody in all IgG subclasses prior and subsequent to the antigen-challenge. Production of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) by lymphoid cells in response to HEL in vitro was markedly suppressed in both the antigen-pretreated groups, while suppression of IL-4 production was evident only in PEG-HEL-, not in HEL-pretreated animals. Involvement of suppressor cells in these tolerance states was found to be unlikely, and the immunological property of PEG-HEL differed from deaggregated HEL that was similar to the original HEL. These results suggest a unique immunotolerogenic activity of PEG-conjugated proteins to suppress both T-helper type-1 (Th1)- and Th2-type responses, the result being extensive inhibition of all IgG subclass responses, while tolerance induction by unconjugated soluble proteins tends to be targeted on Th1-, but spares Th2-type responses.

Adjuvants, Immunologic↗

PubMed1998

Computational imaging of cerebral perfusion by real time processing of DSA images. Clinical applications.

Real time and high resolution functional imaging of cerebral perfusion was developed, which displays the color coded image of the cerebral perfusion index (PI) from the serial images of digital subtraction angiography (DSA). The small (3 x 3 pixels) regions of interest (ROI) were set on the images, and the time density curves of the contrast media for each ROI were obtained. The perfusion indices, corresponding to the mean transit time (MTT), were calculated for all the ROIs on the image in real time (5 sec) by the area over height method and then, converted to the PI image. A large ROI (64 x 64 pixels) was also used to estimate the parenchymal perfusion. In the normal subjects, consistent PI values at the various parts of the cerebral arteries were obtained, which reasonably agreed with the published values when converted to the blood flow. Then the study on the pathological subjects were made. Firstly, the alteration in the PI images agreed well with the CBF SPECT study in the case of moyamoya disease with the synangiosis operation. Secondly, even a 5% change of the parenchymal perfusion could be detected with the PI imaging, which was obscure when inspecting the series of DSA images, in the case of intra-arterial papaverine infusion for delayed vasospasm. Thirdly, the vortex inside a large aneurysm could be estimated with the same resolution as DSA. Our method offers real time, high resolution, projection angle independent and semiquantitative imaging of the cerebral perfusion from the conventional DSA images without introducing any new expensive devices. This method could be used to evaluate the therapeutic change and especially to monitor the rapidly changing cerebral perfusion in interventional angiography.

Aged↗

PubMed1998

Spatial perception in macroscopic and microscopic surgical manipulations: differences between experienced and inexperienced surgeons.

The spatial perceptions of the phantom surgical field with the naked eye and under the surgical microscope were analyzed in a group of experienced and a group of inexperienced neurosurgeons. The phantom surgical field contained a start point, a virtual gate, and a target point. The virtual gate was an invisible zone arbitrarily set in the phantom surgical field. The examinees were first instructed regarding the position of the invisible virtual gate. Then they were asked to point consecutively to the three points with a suction tube under three different circumstances: with the naked eye, under the microscope, and by watching a navigation monitor. A surgical navigator was used to record the three-dimensional position of the suction tip. The pointing deviation from the suction tip to the center of the virtual gate was evaluated. The pointing accuracy with the naked eye did not differ between the two groups, but that under the microscope was significantly better in the experienced group than in the inexperienced group. Fluctuations in pointing deviation were significantly greater in the inexperienced neurosurgeons, especially with the microscope. Further analysis demonstrated that these differences were attributable to poorer depth perception of the phantom surgical space among the inexperienced neurosurgeons.

Clinical Competence↗

PubMed1998

Translucence stereoscopy of interictal magnetoencephalographic epileptiform discharge.

We have developed a translucence stereoscopy method for displaying the distribution of multiple interictal epileptiform discharges within the intracranial space. The epileptiform discharges, measured using a whole-head magnetoencephalography system, were modeled by a least-squares method to obtain the equivalent current dipoles. The dipoles were located in the stereo pair of intracranial images composed of translucent brain slices at several selected levels. The technique demonstrated clearly the distribution of interictal dipoles within the brain in three patients. Three dimensional understanding of the intracranial distribution of multiple dipoles in one image is valuable in analyzing the intracerebral neurophysiological events in epileptic patients.

Adult↗

PubMed1998

Mobile fluoroscopic open stereotaxy for MRI-negative angiographic microlesions.

The approach to the deep-seated angiographic microlesion is often difficult, particularly when it is not demonstrated by computed tomography (CT) or magnetic resonance imaging (MRI). We have developed a method to localize these lesions for open stereotactic surgery employing mobile fluoroscopy. Prior to craniotomy, the patient's head is fixed in a stereotactic frame in a position optimal for the routine microscopic surgery. Following the injection of contrast media, the location of the lesion is marked on the fluoroscope monitor. Under fluoroscopic control, the scalp is marked using radiopaque pointer on each side of the patient's head so that the scalp marks and the target lesion overlap each other on the fluoroscope monitor. Thus the imaginary line connecting these scalp marks passes through the lesion. An additional pair of scalp marks is obtained by changing the projection angle of the fluoroscope. By simple calculation, the coordinates of the lesion are obtained as the nearest point to these two imaginary lines, each of which connects a pair of scalp marks. After craniotomy, the lesion is approached using an open stereotactic technique. The first patient had an aneurysm 1.5 mm in diameter that arose from the feeder of the arteriovenous malformation. The second patient had a small residual nidus of arteriovenous malformation 1.5 cm in diameter in the deep frontal lobe, not recognizable by CT or MRI because of artifacts from a previous surgery. Both patients were successfully operated by employing the present method. This method requires only a conventional stereotactic frame and a mobile fluoroscope, and provides simple and reliable localization of the small lesions recognizable only by cerebral angiography.

Arteriovenous Malformations↗

PubMed1998

Protective effects of a human 18-kilodalton cationic antimicrobial protein (CAP18)-derived peptide against murine endotoxemia.

CAP18 (an 18-kDa cationic antimicrobial protein) is a granulocyte-derived protein that can bind lipopolysaccharide (LPS) and inhibit various activities of LPS in vitro. The present study examined the protective effect of a synthetic 27-amino-acid peptide (CAP18(109-135)) from the LPS-binding domain of CAP18 against antibiotic-induced endotoxin shock, using highly LPS-sensitive D-(+)-galactosamine (D-GalN)-sensitized C3H/HeN mice. The antibiotic-induced endotoxin (CAZ-endotoxin) was prepared from the culture filtrate of Pseudomonas aeruginosa PAO1 exposed to ceftazidime (CAZ). Injection of CAP18(109-135) protected the mice injected with LPS or CAZ-endotoxin from death and lowered their tumor necrosis factor (TNF) levels in serum in a dose-dependent manner. Treatment with CAZ caused death of the D-GalN-sensitized P. aeruginosa PAO-infected mice within 48 h, while injection with CAP18(109-135) rescued the mice from death. In the mice rescued from death by injection with CAP18(109-135), endotoxin levels in plasma and TNF production by liver tissues were decreased but the numbers of viable infecting bacteria in their blood were not decreased significantly and remained at the levels in CAZ-treated mice. These results indicate that CAP18(109-135) is capable of preventing antibiotic-induced endotoxic shock in mice with septicemia and that the effect is due to its LPS-neutralizing activity rather than to its antibacterial activity.

Animals↗

PubMed1998

Evidence for a role of kallikrein-P6nin system in patients with shock after blunt trauma.

Bradykinin (BK) is activated via plasma and/or tissue kallikrein-kinin (K-K) system pathways during hypotension after blunt trauma. The precise role of the K-K system in human subjects has not been defined. We developed a new method for measuring levels of BK in the blood and examined the role of the K-K system in patients with shock after trauma. Eight patients were entered into this study. We measured the levels of a high-molecular-weight kininogen (HMWK), a low-molecular-weight kininogen (LMWK), BK, and (1-5)-BK in the blood of patients in an unstable state (Pre) and a stable state (Post). At Pre, the blood BK level was significantly elevated, the HMWK and LMWK levels were significantly lower, and the (1-5)-BK level was significantly higher than the respective levels at Post. Our data suggest a significant role for the K-K system in the pathogenesis of shock after blunt trauma. This newly developed method for determination of the activation of the plasma K-K system appears to be useful for determining the severity of a trauma.

APACHE↗

PubMed1998

Epithelial rests colocalize with cementoblasts forming acellular cementum but not with cementoblasts forming cellular cementum.

Epithelial rests of Malassez and cementoblasts were examined in the rat molars during the early stages of root formation using an antilaminin antibody and/or peanut agglutinin (PNA), and an antiosteocalcin (OC) antibody, respectively. The roots of the first molars were used for study. The antilaminin antibody stained the basement membrane surrounding the epithelial root sheath and epithelial rests. The basement membrane of the epithelial root sheath was continuous, but that of the epithelial rests was discontinuous. The cells of epithelial rests and epithelial root sheath were positive for PNA. The structural characteristics of the epithelial rests were seen in the sections stained doubly with PNA and the antilaminin antibody. The cells of epithelial rests were fibroblast-like and formed a fine mesh in 2-week-old rats. In 3-week-old rats, the epithelial rests were also present at the coronal half of root surface, showing typical cell cords, but were not present at the apical part of the root surface where the cellular cementum covered the root dentin. At the root apex of 3-week-old rats, the cells of epithelial rests forming fine meshes were seen near the epithelial root sheath. The anti-OC antibody stained cementoblasts lining acellular and cellular cementum. The sections doubly stained with the anti-OC and the antilaminin antibodies or PNA further revealed the close relation between epithelial rests and cementoblasts. The OC-positive cells lining acellular cementum or dentin were localized very close to the epithelial rests. In contrast, the OC-positive cells lining cellular cementum did not show close association with the epithelial cells, except the cells located most apically where the basement membrane of the epithelial root sheath is disrupted and the initial cellular cementum begins to be formed. The present results suggest that the epithelial rests and/or the discontinuous basement membrane of them may have a role for the acellular cementum formation at least in the early stage of root formation.

Animals↗

PubMed1998

Pleckstrin homology domain as an inositol compound binding module.

Many of the proteins that participate in cell signalling contain structural modules involved in regulatory interactions between components of signal transduction cascades. One of such modules is the pleckstrin homology (PH) domain, a region of approximately 120 amino acids that can form an electrostatically polarized tertiary structure. Several molecules such as inositol 1,4,5-trisphosphate/phosphatidylinositol 4,5-bisphosphate, the betagamma-subunits of heterotrimeric G proteins and protein kinase C have been proposed as common ligands for the PH domain. Through these potential interactions, the PH domain has been proposed to play a role in membrane recruitment of proteins containing the PH domain, thus targeting them to appropriate cellular compartment or enabling them to interact with other components of the signal transduction pathway. In this review, we mainly focus on membrane targeting through the binding to inositol phosphates/phosphoinositides.

Amino Acid Sequence↗

PubMed1998

Glioblastoma following radiotherapy in a patient with tuberous sclerosis.

A 26-year-old male with tuberous sclerosis developed a glioblastoma in the right temporal lobe 8 years after surgical excision and irradiation of a subependymal giant cell astrocytoma. The glioblastoma was probably an irradiation-induced tumor. Irradiation should not be given routinely for subependymal giant cell astrocytoma.

Adult↗

PubMed1998

Affected segments of the median nerve detected by fractionated nerve conduction measurement in vibration-induced neuropathy.

Peripheral neuropathy in the hand has often been reported in workers using hand-held vibrating tools. But the affected location in the hand is not clearly demonstrated. To elucidate the impaired segment of the median nerve within the hand, fractionated median sensory nerve conduction velocity (SCV) was measured in the digital, finger-to-palm, palm-to-wrist and wrist-to-elbow segments. Subjects were 56 patients with hand-arm vibration syndrome and 43 healthy controls of similar age. SCV in the digital and the wrist-to-palm segments was significantly slower in the patients than the controls. Slowed SCV in the digital segment was encountered in 36% of the patients, while the slowing in SCV in the wrist-to-palm segment (across the carpal tunnel) was found in 20% of them. The slowing in the digital segment was more frequently encountered in the advanced stage of the Stockholm sensorineural (SN) stage for hand-arm vibration syndrome: 10% in 0SN (no neurological symptoms) while 56% in 3SN (severe stage). The present study has demonstrated that vibration-induced nerve impairments dominantly exist both in the digits and across the carpal tunnel. Careful neurophysiological assessment is important to confirm the impaired location within the hand.

Adult↗

PubMed1998

A probable case of chronic occupational thallium poisoning in a glass factory.

A male worker who handled thallium-containing raw material for glass manufacturing over a period of four years complained of alopecia, abdominal pain, diarrhea and tingling in the four extremities. Neurological examination of this patient revealed signs of mild glove-stocking-type polyneuropathy. Lower sensory nerve conduction velocity of the median nerve in the right hand than in the left hand suggested that conduction function in the dominant hand was reduced. The thallium content of the hair, as determined by an ICP-MS method, was 20 ng/g for the patient and 576 ng/g for his successor in the time of 32 months and 13 months, respectively, after they had ceased their glass production work. Those levels of thallium exposure were considered high, compared with the control levels so far reported. The clinical course of signs and symptoms, neurophysiological findings and thallium content of hair suggested that the patient suffered from chronic poisoning due to occupational exposure to thallium-containing dust.

Abdominal Pain↗

PubMed1998

Immune function and lifestyle of taxi drivers in Japan.

Many studies have reported that stress affects the immune system. It is known that professional drivers are exposed to various forms of job-related stress. The aim of the present study was to investigate the job stress of taxi drivers based on the mitogen responses and cytokine production of peripheral blood lymphocytes (PBMC), combined with interviews on lifestyles and income. We examined randomly selected male taxi drivers aged 40-59 years who were members of the Kansai District Union of Private Railway, Hire, and Taxi at the end of 1992 and 1993. At the end of 1993, they were struck by a severe economic depression. The lymphocyte proliferative responses to phytohemagglutinin (PHA), concanavalin A (ConA), poke weed mitogen (PWM), and PHA-induced interleukin-2 (IL-2) and IL-4 production of the taxi drivers were at the same level as those of the control subjects as measured in 1992. The mitogen responses and IL-2 production of taxi drivers were found to have significantly decreased in 1993, while their IL-4 production was significantly elevated. Lifestyles of normal PHA respondents were significantly different from those of low-PHA respondents in 1992. However, in 1993, these differences were unclear. The immune alterations of taxi drivers who were prohibited from working overtime were more profound than those of the drivers who were allowed to do so. These results indicate that in addition to driving stress, the daily earnings affect taxi drivers as a strong stress or that induces immunological changes.

Adult↗

PubMed1998

O/W lipid emulsions for parenteral drug delivery. IV. Changes in the pharmacokinetics and pharmacodynamics of a highly lipophilic drug, menatetrenone.

The pharmacokinetics and pharmacodynamics of antihemorrhagic vitamin, menatetrenone after intravenous injection as the lipid emulsion, were compared to those as the micellar solutions. Menatetrenone was selectively delivered to the liver, lungs and spleen and retained in them. Hepatic and splenetic concentration at 6 h (C6h) increased 21.6- and 27.1-fold, respectively, and the area under the tissue concentration-time curve up to 6 h (AUC(0-6h)) were 2.3- and 11.4-fold, respectively, when compared with its micellar solution. Antihemorrhagic effect of menatetrenone was assessed using warfarin-induced hypoprothrombinemic rats. The lipid emulsion of menatetrenone decreased the prothrombin time at 6h after intravenous injection more effectively than micellar solution. The dose response curves indicated that the efficacy of the lipid emulsion was 2.4-2.9 times that of a micellar solution, and this was correlated with AUC(0-6h) rather than C6h. The plasma level of clotting factor VII and the hepatic level of descarboxyprothrombin were also recovered more effectively, while no significant differences were noted between the two formulations for the plasma level of factor II or descarboxyprothrombin at the dose levels examined. Although selective delivery of menatetrenone in the liver by the lipid emulsion was due to phagocytosis by non-parenchymal cells, menatetrenone in the whole liver appeared to contribute to recovery from hypoprothrombinemia.

Analysis of Variance↗

PubMed1998

The inhibitory effects of pravastatin on natural killer cell activity in vivo and on cytotoxic T lymphocyte activity in vitro.

BACKGROUND: We have reported that heart transplant recipients treated with pravastatin demonstrate decreases in the incidence of clinically severe acute rejection episodes, the incidence and progression of transplant coronary vasculopathy, and natural killer cytotoxicity. These patients also exhibited a significant improvement in 1-year allograft survival. Because of these clinical findings suggesting an immunosuppressive effect of pravastatin unique to transplant recipients and the unclear role of natural killer cells in allograft rejection, we postulated that pravastatin may exert its immunomodulatory effect by acting with cyclosporine to alter T lymphocyte function. METHODS: Twenty patients randomized into an ongoing trial of pravastatin after heart transplantation were monitored serially for natural killer cell cytotoxicity. In a separate experiment, lymphocytes isolated from normal volunteers were treated with various combinations of pravastatin and cyclosporine and tested for cytotoxic T lymphocyte toxicity in a one-way mixed lymphocyte reaction. RESULTS: Pravastatin-treated heart transplant recipients exhibited a decrease in natural killer cell cytotoxicity (9.8% mean natural killer cell cytotoxicity vs 22.1% in the control group, p < 0.01). In the one-way mixed lymphocyte reaction with blood obtained from control subjects, there was a synergistic inhibition of cytotoxic T lymphocyte activity when the cells were cultured in a combination of pravastatin and cyclosporine (20.3% mean cytotoxicity of target cells vs 41.4% in the control group, p < 0.01). CONCLUSIONS: Pravastatin exerts an immunosuppressive effect in heart transplant recipients as expressed by a reduction in rejection and natural killer cell cytotoxicity. Pravastatin and cyclosporine act synergistically to reduce cytotoxic T lymphocyte activity. This synergistic effect of pravastatin and cyclosporine may explain why this immunosuppressive effect is unique to transplant recipients.

Adjuvants, Immunologic↗

PubMed1998

[Discrepancy between surgeon's binocular parallax perception and manipulation in the neurosurgical operation].

The application of virtual reality (VR) to the neurosurgical field has been increasing recently, however, the relation between the surgeon and the VR environment is rarely studied. We examined the trajectory of a surgical instrument during manipulation of a virtual object using a video-see-through microscope and a neurosurgical navigator (CANS Navigator) to find better surgeon-microscope interface. A resin cylindrical phantom was produced representing the surgical field, which included two 3 dimensionally arranged small spheres and a virtual 'gate'. The phantom was fixed and set under the microscope with a skull clamp mimicking conditions in an ordinary craniotomy. Firstly, the binocular parallax perception under microscope was examined. Experienced and inexperienced neurosurgeons were asked to learn the position of the virtual 'gate' for 3 minutes. Then, after 5 minutes to point with the navigator probe (suction tube), under various conditions; under the naked eyes, under the microscope, under the navigator without observing the phantom, and under the microscope with picture in picture (PIP) display of the navigational image. The positions of the suction tube were recorded at real time into the navigator for later analysis. Secondly, the task performance in this VR environment was studied by analyzing the trajectory of the suction tube from one sphere to the other sphere passing the virtual 'gate' under various conditions. A significant difference in pointing precision between experienced and inexperienced neurosurgeons was able to be observed only under microscope. This difference was mainly derived from overestimation of the depth of the virtual 'gate' by the inexperienced neurosurgeons. Among the above conditions, pointing under the microscope with PIP was able to be performed the most precisely and the most promptly. This study disclosed the presence of stereoscopic distortion in the microscope. The PIP display of the navigational image in the microscopic view remarkably improved the task performance, which could be accounted for by the correction of the somewhat distorted binocular parallax perception under the neurosurgical microscope by the provision of another visual key.

Brain↗

PubMed1998

[Pryce type I interlobar pulmonary sequestration with anomalous return to the left inferior pulmonary vein].

A 50-year-old woman was examined because of chest discomfort. Chest X-ray films disclosed a tumorous shadow behind the heart. Chest computed tomography (CT) scans revealed a mass connected to the descending aorta, with increased blood flow in the left basal segment. The patient was admitted for further examination. Chest CT scans and cardioscintigrams were very useful as diagnostic tools, but the final diagnosis was made on the basis of angiography. An anomalous tortuous artery ran from the descending aorta into the left basal segment and returned to the left inferior pulmonary vein. The left pulmonary arterial trunk had no basal branch (A8-A10). A loop corresponding to the superior vein (V6) ran beneath the anomalous tortuous artery. To our knowledge, this is the second case of Pryce type-I interlobar pulmonary sequestration with anomalous return to the left inferior pulmonary vein to be reported in Japan. A left inferior lobectomy was performed. Histological finding from the excised tissues showed prominent interstitial fibrosis, atypical adenomatous hyperplasia, and atherosclerosis. Following surgery, the patient's PaO2 increased from 80.4 Torr to 95.8 Torr, suggesting that left inferior lobectomy was an appropriate treatment.

Bronchopulmonary Sequestration↗