Biomedical subjects

T Kawamata

Publications and source records attributed to T Kawamata.

At least 37 records · Page 2Linked to original sources

PubMed2002

Flexible endoscope-assisted endonasal transsphenoidal surgery for pituitary tumors.

We have performed rigid endoscope-assisted endonasal transsphenoidal microsurgeries for pituitary tumors in 230 patients. Recently, we further introduced the use of a flexible endoscope to inspect the tumor bed and suprasellar structures more extensively. We report our experience with the flexible endoscope in endonasal transsphenoidal surgery for pituitary tumors. The endoscopes were used to complement the microscope in visualization. The flexible endoscopes were used in 34 recent cases with suprasellar and/or lateral tumor extension. During or after removal of the main tumor bulk, the flexible endoscope together with a rigid endoscope was used to inspect the tumor cavity, especially at the blind spot of the microscope. Despite limited resolving power, in all the 34 cases the flexible endoscope was a highly efficient tool permitting extensive visualization of almost the whole surgical area, even in narrow surgical fields and spaces not visible with an operating microscope or a rigid endoscope, and allowing continuous change of viewing angle. The residual tumor situated laterally or in the suprasellar areas that could not be reached and was impossible to remove by a rigid endoscope could be dissected and extirpated under a flexible endoscope using grasping forceps in 5 patients with pituitary adenoma and all the craniopharyngioma cases. The flexible endoscope may be more efficient in the lateral and suprasellar areas than the rigid endoscope in compensating for the narrow surgical field in endonasal pituitary surgery, despite its limited resolving power. Surgeons should make the best use of the advantages of each instrument.

Adenoma↗

PubMed2001

Involvement of capsaicin-sensitive fibers in spinal NMDA-induced glutamate release.

The activation of spinal NMDA receptors can evoke glutamate release through the production of nitric oxide (NO) within the spinal cord, resulting in pain-relating behavior. In this study, we investigated the involvement of capsaicin-sensitive primary afferents in this phenomenon using in vivo intrathecal microdialysis. Intrathecal NMDA perfusion evoked increases in the concentrations of NO metabolises and glutamate and in pain-related behavior in both neonatal capsaicin and vehicle-treated rats. Although the degrees of increase in NO metabolises in capsaicin- and vehicle-treated rats were not significantly different, capsaicin-treated rats showed significantly smaller increases in glutamate concentration and pain-related behavior than did vehicle-treated rats. Our results showed that glutamate release from capsaicin-sensitive primary afferent terminals is involved in spinal NMDA-induced pain.

Animals↗

PubMed2001

Peripheral nitric oxide in carrageenan-induced inflammation.

Recent studies have suggested that nitric oxide (NO) peripherally produced by different nitric oxide synthase (NOS) isoforms contributes to edema formation and development of hyperalgesia. The present study was designed to examine the effects of NOS isoforms on NO release in carrageenan-induced inflammation at various time points. A microdialysis probe was implanted subcutaneously into the glabrous skin of hindpaws of Sprague-Dawley rats under pentobarbital anesthesia. After sample collection to obtain the basal level of the total amount of nitrite and nitrate (NO2-/NO3-), modified Ringer solution, a non-selective NOS inhibitor, NG monomethyl-L-arginine acetate (L-NMMA), or an iNOS inhibitor, aminoguanidine hemisulfate (AG) was perfused through the microdialysis probe. 2 mg of carrageenan was injected into the plantar surface of the probe-implanted hindpaw. Carrageenan was also injected in rats that had undergone sciatic nerve sectioning. Carrageenan significantly increased the dialysate concentrations of NO2-/NO3- for more than 8 h. L-NMMA suppressed the carrageenan-induced increase in NO2-/NO3- concentration. Although AG did not suppress the increase in NO2-/NO3- for the first 2 h after carrageenan injection, significant suppression of the increase in NO2-/NO3- was observed from 2.5 h after carrageenan injection. In the rats in which the sciatic nerves had been denervated, the increases in concentrations of NO2-/NO3- were completely suppressed up to 3 h and partially suppressed 4.5-8 h after carrageenan injection. The results of the current study show that carrageenan induces peripheral release of NO, the production of which is mediated by nNOS in the early phase and by both nNOS and iNOS in the late phase of carrageenan-induced inflammation.

Animals↗

PubMed2001

Microglial signaling by amyloid beta protein through mitogen-activated protein kinase mediating phosphorylation of MARCKS.

Myristoylated alanine-rich C kinase substrate (MARCKS), an acidic protein associated with cell motility and phagocytosis, is activated upon phosphorylation by protein kinase C (PKC) and proline-directed protein kinases. In Alzheimer disease (AD), activated microglia expressing MARCKS migrates around senile plaques. We reported that amyloid beta protein (A beta), a major component of senile plaques, activated MARCKS through a tyrosine kinase and PKC-delta. We have now identified another A beta signaling pathway through a mitogen-activated protein kinase (MAPK) involved in the phosphorylation of MARCKS and analysed cross-talk between PKC and MAPK pathways in primary cultured rat microglia. A selective inhibitor for MAPK kinase, PD098059, significantly inhibited the phosphorylation of MARCKS induced by A beta. Extracellulary regulated kinases, the activities of which were induced by A beta, directly phosphorylated a recombinant MARCKS in vitro. The MAPK pathway was sensitive to wortmannin, but not to a PKC inhibitor or to tyrosine kinase inhibitors. The activation of PKC by A beta was not sensitive to wortmannin. Our findings suggest involvement of the MAPK pathway through phosphoinositol 3-kinase in the phosphorylation of MARCKS in rat cultured microglia, an event may be associated with mechanisms activating microglia in AD.

Amyloid beta-Peptides↗

PubMed2001

Amyloid beta protein activates PKC-delta and induces translocation of myristoylated alanine-rich C kinase substrate (MARCKS) in microglia.

The increased accumulation of activated microglia containing amyloid beta protein (Abeta) around senile plaques is a common pathological feature in subjects with Alzheimer's disease (AD). Much less is known, however, of intracellular signal transduction pathways for microglial activation in response to Abeta. We investigated intracellular signaling in response to Abeta stimulation in primary cultured rat microglia. We found that the kinase activity of PKC-delta but not that of PKC-alpha or -epsilon is increased by stimulation of microglia with Abeta, with a striking tyrosine phosphorylation of PKC-delta. In microglia stimulated with Abeta, tyrosine phosphorylation of PKC-delta was evident at the membrane fraction without an overt translocation of PKC-delta. PKC-delta co-immunoprecipitated with MARCKS from microglia stimulated with Abeta. Abeta induced translocation of MARCKS from the membrane fraction to the cytosolic fraction. Immunocytochemical analysis revealed that phosphorylated MARCKS accumulated in the cytoplasm, particularly at the perinuclear region in microglia treated with Abeta. Taken together with our previous observations that Abeta-induced phosphorylation of MARCKS and chemotaxis of microglia are inhibited by either tyrosine kinase or PKC inhibitors, our results provide evidence that Abeta induces phosphorylation and translocation of MARCKS through the tyrosine kinase-PKC-delta signaling pathway in microglia.

Amyloid beta-Peptides↗

PubMed2001

Injuries to the posterolateral aspect of the knee accompanied by compression fracture of the anterior part of the medial tibial plateau.

We present 12 cases of patients with injury to the posterolateral aspect of the knee accompanied by a compression fracture of the anterior part of the medial tibial plateau. There were 11 male patients and 1 female patient with an average age of 26 years (range, 17 to 44 years). There were 4 cases of posterolateral rotatory instability and 8 cases of straight lateral instability of the knee. The size of the compression fracture was classified into 2 types, small (8 cases) and large (4 cases). Although the mechanism of injury was considered to be hyperextension and varus force, the pattern of cruciate ligament injuries varied from case to case. The following 3 questions should be considered to determine which cruciate ligament is damaged: (1) Was the ipsilateral foot fixed to the ground? (2) Was forward inertia involved? (3) Was there a direct blow to the anteromedial aspect of the tibia or to the femur? Accompanied fractures of the medial tibial plateau were considered to have been compressed by the medial femoral condyle. The size of the accompanying compression fracture varied; 7 of 8 cases with a small-type fracture had posterior cruciate ligament injuries and 3 of 4 cases with a large-type fracture had anterior cruciate ligament injuries. The size of the fracture is determined by which point of the medial tibial plateau touched the medial femoral condyle. We propose that a compression fracture of the anterior part of the medial tibial plateau indicates a coexistent posterolateral aspect injury, and that especially a small compression fracture strongly suggests an accompanying posterior cruciate ligament injury, as well.

Adolescent↗

PubMed2001

Surgical treatment of falcotentorial meningioma.

Meningiomas arising from the falcotentorial junction are rare. Among our surgical experience of 375 meningiomas, only 4 cases of so-called falcotentorial meningiomas were encountered. We present these four surgical cases. An occipital transtentorial approach was used in three cases, and a combined midline occipital and suboccipital approach in one case. Total tumour excision was impossible in two cases because of engulfing deep venous structures including the great vein of Galen. Postoperative Gamma knife radiosurgery was performed in these two cases. On the other hand, a posteriorly located tumour was relatively easy to remove, and macroscopic total removal was accomplished. In conclusion, precise microvascular anatomical knowledge is indispensable to satisfactorily excise meningiomas in the falcotentorial area without significant morbidity.

Craniotomy↗

PubMed2001

Acute respiratory and metabolic acidosis induced by excessive muscle contraction during spinal evoked stimulation.

Spinal somatosensory evoked potentials (SSEPs) have been used to monitor spinal cord function during corrective scoliosis surgery. We report three cases in which direct epidural stimulation for measurement of SSEPs produced paraspinal muscle contraction, resulting in respiratory and metabolic acidosis. In two of the cases, SSEP-induced acidosis was observed even when only the first twitch of the train-of-four response was detectable after a second dose of muscle relaxant. In one of these two cases, the acidosis was abolished after a sufficient dose of vecuronium to ablate the twitch response. To prevent SSEP-induced respiratory and metabolic acidosis, we recommend that SSEPs should be measured only when profound neuromuscular blockade has been obtained.

Acidosis↗

PubMed2001

The effects of peripheral administration of a novel selective antagonist for prostaglandin E receptor subtype EP(1), ONO-8711, in a rat model of postoperative pain.

UNLABELLED: Mechanically evoked pain, also known as incident pain, induced by coughing or deep breathing after surgery leads to potentially devastating consequences. It is generally thought that the prostaglandin receptor- (especially, the receptor for prostaglandin E(2), EP receptor) mediated sensitization of sensory nerve fibers is a key contributor to the generation of hyperalgesia. We examined whether a peripherally administered novel selective EP(1) antagonist, ONO-8711, would be a potential analgesic for incision-induced mechanical hyperalgesia. We used a rat model of postoperative pain introduced by Brennan et al. (1). Withdrawal thresholds to punctate stimulation and response frequencies to nonpunctate mechanical stimulation were determined by using von Frey filaments applied adjacent to the wound and directly to the incision site of the hind paw, respectively. Mechanical hyperalgesia to punctate and nonpunctate stimuli was observed 2 and 24 h after the incision. ONO-8711 (2, 10, or 50 microg) or saline was administered subcutaneously into the hind paw on the ipsilateral side to the incision. ONO-8711 significantly (P < 0.01) increased the withdrawal thresholds to punctate mechanical stimulation and significantly (P < 0.01) decreased the response frequencies to nonpunctate mechanical stimulation in a dose- and time-dependent manner 2 and 24 h after the incision. We conclude that EP(1) receptor-mediated sensitization of sensory nerve fibers may contribute to the generation of mechanical hyperalgesia produced by incisional surgery, and that the EP(1) receptor antagonist ONO-8711 may be an option for treatment of postoperative pain, especially incident pain. IMPLICATIONS: The peripheral administration of an antagonist for EP(1) receptor that is a subtype of prostaglandin E receptors can inhibit the mechanical hyperalgesia induced by a surgical incision.

Animals↗

PubMed2001

Radial displacement of the medial meniscus in varus osteoarthritis of the knee.

The macroscopic and histologic findings for 31 medial menisci and medial tibial plateaus obtained during total knee arthroplasty were examined to clarify the etiology and progression of varus osteoarthritis. Medial menisci were preserved fairly well in cases of severe osteoarthritis in which the medial joint space had already disappeared. The anterior segment was preserved in 26 (84%) menisci and the posterior segment was preserved in 11 (35%). The medial meniscus may have been preserved because of its radial displacement. Exposure of subchondral bone of the medial tibial plateau occurred in all 31 knees. The exposure of subchondral bone was centered in the anterior, middle, and posterior in nine, 10, and 12 medial tibial plateaus, respectively. There was a mechanical inconsistency between the pattern of preservation of the medial menisci and the location of exposure of subchondral bone on the medial tibial plateaus. The inconsistency reflects that the segment of the medial meniscus on which the excessive load was considered to exist was preserved fairly well. The authors' hypothesis for explaining this inconsistency is that radial displacement of the medial meniscus precedes narrowing of the medial joint space during progression of varus osteoarthritis, so that the displaced meniscus is saved from severe degeneration or attrition.

Aged↗

PubMed2001

Patent foramen ovale as a possible risk factor for cryptogenic brain abscess: report of two cases.

OBJECTIVE AND IMPORTANCE: Patent foramen ovale (PFO) has been suggested as a potential source of paradoxical embolism. A higher prevalence of PFO in ischemic stroke of unexplained cause has been recognized. Brain abscesses are commonly associated with a contiguous focus of infection, hematogenous spread from a distant focus, or cranial trauma. However, no predisposing factors, including a distant focus with unknown cause, are identified in approximately 15 to 30% of reported cases. CLINICAL PRESENTATION: We encountered two patients with brain abscess presumably caused by dental infections. Both patients displayed PFO, through which right-to-left atrial contrast shunting was revealed by transesophageal echocardiography. Although the radiological location of the abscesses suggested hematogenous spread as a cause, the patients had no arteriovenous shunting other than the PFO, despite exhaustive investigations for a potential infectious route. The patients displayed no definite focal orofacial inflammatory signs during the postoperative course despite diagnosis of pyorrhea alveolaris or periodontitis. INTERVENTION: In Patient 1, the abscess was aspirated stereotactically, and in Patient 2, the abscess disappeared radiologically after high-dose antibiotic treatment. CONCLUSION: The mechanism of brain abscess formation putatively related to PFO should be different from that related to common dental sepsis. Analysis of these cases suggested that infectious embolism from a latent or even identifiable focus through the PFO may be an underrecognized cause of brain abscess, in contrast to simple seeding of the brain via transit of the infecting bacteria through the valveless emissary veins.

Adult↗

PubMed2001

New possibilities for stereotaxis. Information-guided stereotaxis.

Information-guided stereotaxis, assisted by visualization of medical information, will become the next generation of neurosurgical systems. We performed 76 open MRI surgeries at Tokyo Women's Medical University between March 3, 2000 and April 12, 2001. Of them, comparisons of pre- and post-operative MR images for malignant gliomas in 21 cases revealed an average resection rate of 90.3% (the maximum 100%, the minimum 55%). In this article we describe real time updated navigation, augmented reality navigation, three-dimensional navigation, chemical navigation, information-guided navigation system (High definition visual Computer Aided Surgery System: HivisCAS), and open MRI-guided surgery that we are developing.

Humans↗

PubMed2001

Clinical application of an ultrasonically activated scalpel in neurosurgery.

Ultrasonically activated scalpel (UAS) is a surgical device utilizing ultrasonic energy to cut and coagulate tissues simultaneously. The actions and features of UAS are considerably different from those of conventional ultrasonic cavitational aspirators (UCA) that have been used frequently in the neurosurgical field. The UAS has been used routinely in a number of general surgeries, including laparoscopic surgeries and open surgeries of the lung and liver. However, neurosurgical application of UAS has not been reported. We used UAS in surgical resection of intracranial tumors consisting of five meningiomas, two gliomas, and one metastatic brain tumor, and monitored thermal changes in tissues using thermoencephaloscopy to investigate the possibility of heat injury by UAS. It was used to achieve both dissection of the attachment of meningiomas and internal decompression of the tumors and allowed efficient resection of various tumors with minimal bleeding by adjustment of the combination of coagulation and cutting powers at five different positions. The attachment of meningiomas was coagulated and cut easily and safely by UAS. Moreover, infrared thermographic study showed that the degree of temperature increase and the area of elevated temperature were extremely limited in UAS. The current study suggests that it is a promising device in neurosurgery.

Body Temperature↗

PubMed2001

Time courses of increased expression of signaling transduction molecules induced by basic fibroblast growth factor in PC12 cells.

We previously demonstrated that basic fibroblast growth factor (bFGF) protected neuronal injury in in vivo experimental cerebral ischemia. The precise molecular mechanisms of the neuroprotective effect of bFGF, however, remains unsolved. We investigated time courses of up-regulated molecules involved in intracellular signaling transduction pathways induced by bFGF in PC12 cells to explore the possible neuroprotective mechanism of bFGF action. In Western blot analysis, bFGF increased expression of Ras mainly in the early stage up to 24h, returning to the baseline level at 48 h. Expression of phosphatidylinositol 3-kinase (PI 3-kinase) was enhanced throughout the early and later stages, and was more up-regulated at 48 h compared to 24 h. The present findings suggest that bFGF might promote cell survival or proliferation mainly via Ras, and PI 3-kinase might be involved in cell survival and differentiation in PC12 cells.

Animals↗

PubMed2001

Prodromal signs and clinical factors influencing outcome in patients with intraventricular rupture of purulent brain abscess.

OBJECTIVE: To elucidate prodromal signs and clinical factors influencing the prognosis in patients with intraventricular rupture of brain abscess (IVROBA) to prevent and manage this catastrophic condition. METHODS: In this study, 33 consecutive patients with IVROBA diagnosed by computed tomography (CT) were treated. Basic and therapeutic parameters were evaluated as independent predictive factors of a poor prognosis by using univariate analysis. The factors were statistically analyzed based on the interval between initial symptoms and IVROBA. RESULTS: Patients with a good outcome were younger (<21 yr old) (P < 0.003) and had fewer complications after IVROBA (P < 0.03). For the most part, these patients had undergone aspiration for brain abscess with ventricular drainage combined with the immediate administration of appropriate intravenous and intrathecal antibiotics (P < 0.02). In just a short time, abscesses located in the parieto-occipital region ruptured into the ventricle (P < 0.004), and those with nonsterile cultures (P < 0.01) developed into IVROBA. Just before IVROBA, patients had severe headaches, signs of meningeal irritation, and a rapidly deteriorating clinical condition within 10 days after the signs of meningeal irritation developed. A CT scan obtained before IVROBA ascertained localized enhancement of the ventricular wall adjacent to the abscess. CONCLUSION: Our findings suggest that signs of meningeal irritation and localized enhancement of the ventricular wall adjacent to the abscess, as observed on CT scans, preceded IVROBA. To decrease the mortality rate associated with purulent brain abscesses, signs forewarning of IVROBA should be recognized, and aggressive management of IVROBA should be initiated. Aggressive CT-guided aspiration of deep-seated abscesses, particularly in the parieto-occipital region, at the time forewarning signs of IVROBA are observed lead to the prevention of IVROBA and an improvement in outcome.

Adolescent↗

PubMed2001

[The effect of continuous intra-articular and intra-bursal infusion of lidocaine on postoperative pain following shoulder arthroscopic surgery].

We evaluated the effects of continuous intra-articular and intra-bursal infusion of lidocaine on postoperative pain following shoulder arthroscopic surgery. Forty-one ASA I-II patients scheduled for shoulder arthroscopic surgery, were allocated into following four groups. The patients, after intra-articular arthroscopic surgery, either received intra-articular lidocaine (Group I, n = 10) or did not (Group III, n = 10). The patients after extra-articular arthroscopic surgery either received intra-bursal lidocaine (Group II, n = 11) or did not (Group IV, n = 10). Group I and Group II received 8 ml of 1% lidocaine intra-articularly and intra-bursally, respectively, at the end of surgery, followed by continuous infusion of 1% lidocaine at the rate of 2 ml.hr-1 for 24 hours. The intensities of postoperative pain were evaluated by Visual Analogue Scale (VAS), 2, 5, 8, 12, 18 and 24 hours after surgery, and by the number of patients' request for supplemental analgesic for 24 hours. The VAS scores and the number of analgesic requests were significantly lower (P < 0.05) in Group I than Group III, and in Group II than Group IV throughout the postoperative observation period. No adverse effects were observed during this study. We conclude that continuous intra-articular and intra-bursal infusion of lidocaine provides effective postoperative pain relief for shoulder arthroscopic surgery.

Adult↗

PubMed2001

[Anesthetic management of a patient with Crow-Fukase syndrome complicated with severe heart failure].

A 31-year-old man with Crow-Fukase syndrome was scheduled for orthopedic surgery of the right lower limb. Preoperative examination revealed severe heart failure due to cardiomyopathy. Anesthesia was maintained with sevoflurane and nitrous oxide in oxygen, and supplemental fentanyl combined with continuous epidural block. During surgery, we evaluated cardiac function using transesophageal echocardiography. To maintain his cardiac function, intravenous dopamine and dobtamine were administered continuously, and the surgery was performed successfully. We must take care of cardiac function during anesthetic management of a patient with this syndrome.

Adult↗

PubMed2000

Phosphorylation of tau is regulated by PKN.

For the phosphorylation state of microtubule-associated protein, tau plays a pivotal role in regulating microtubule networks in neurons. Tau promotes the assembly and stabilization of microtubules. The potential for tau to bind to microtubules is down-regulated after local phosphorylation. When we investigated the effects of PKN activation on tau phosphorylation, we found that PKN triggers disruption of the microtubule array both in vitro and in vivo and predominantly phosphorylates tau in microtubule binding domains (MBDs). PKN has a catalytic domain highly homologous to protein kinase C (PKC), a kinase that phosphorylates Ser-313 (= Ser-324, the number used in this study) in MBDs. Thus, we identified the phosphorylation sites of PKN and PKC subtypes (PKC-alpha, -betaI, -betaII, -gamma, -delta, -epsilon, -zeta, and -lambda) in MBDs. PKN phosphorylates Ser-258, Ser-320, and Ser-352, although all PKC subtypes phosphorylate Ser-258, Ser-293, Ser-324, and Ser-352. There is a PKN-specific phosphorylation site, Ser-320, in MBDs. HIA3, a novel phosphorylation-dependent antibody recognizing phosphorylated tau at Ser-320, showed immunoreactivity in Chinese hamster ovary cells expressing tau and the active form of PKN, but not in Chinese hamster ovary cells expressing tau and the inactive form of PKN. The immunoreactivity for phosphorylated tau at Ser-320 increased in the presence of a phosphatase inhibitor, FK506 treatment, which means that calcineurin (protein phosphatase 2B) may be involved in dephosphorylating tau at Ser-320 site. We also noted that PKN reduces the phosphorylation recognized by the phosphorylation-dependent antibodies AT8, AT180, and AT270 in vivo. Thus PKN serves as a regulator of microtubules by specific phosphorylation of tau, which leads to disruption of tubulin assembly.

Amino Acid Sequence↗