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Biomedical subjects

J Tanaka

Publications and source records attributed to J Tanaka.

At least 181 records · Page 10Linked to original sources
PubMed1999

Operative results of canal-expansive laminoplasty for cervical spondylotic myelopathy in elderly patients.

STUDY DESIGN: The study involved elderly patients (age > or = 65), who underwent treatment for cervical spondylotic myelopathy by canal-expansive laminoplasty. OBJECTIVES: To determine the factors that influence the operative results of canal-expansive laminoplasty for treatment of cervical spondylotic myelopathy in elderly patients. SUMMARY OF BACKGROUND DATA: Although there have been previous reports of many operative procedures, to the authors' knowledge there are no reports on the results of surgical treatment for cervical spondylotic myelopathy in elderly patients, treated by a unified surgical procedure. To date, no attempts have been made to predict the results of these procedures. METHODS: Forty-seven patients (age > or = 65) who underwent canal-expansive laminoplasty were reviewed in this study. The severity of the clinical picture and the quality of operative results were graded according to the Japanese Orthopaedic Association scoring system. RESULTS: Of the 13 patients whose period of disability persisted for less than 3 months before the operation, 12 were able to walk after surgery. The operative results of patients more than 80 years of age were not significantly different from those of patients aged between 65 and 79 years. Results of multiple regression analysis indicate that the predictive probability of the postoperative motor function score of the lower extremities was 70%. CONCLUSIONS: The severity of the clinical picture and the duration of symptoms influenced the outcome of the operation. Despite the advanced age of some patients (> 80), the operation increased the chance of recovery from the disease.

Aged↗
PubMed1999

Construction of Epstein-Barr virus-based expression vector containing mini-oriP.

Epstein-Barr virus (EBV)-based vectors are extrachromosomal vectors carrying a replicational origin, oriP (about 2200 bp) and a replication initiation factor (EBNA-1) which are sufficient for autonomous replication. Because one disadvantage of these vectors is their large sizes, we examined the effect of partial deletion of oriP on the effectiveness of the EBV-based vectors, using an enhanced green fluorescent protein (EGFP) as a reporter to monitor gene expression. Results indicated that 954 bp-deleted mini-oriP is useful in primate cells since the vector showed high efficiency of stable transfection, a high ratio of EGFP-positive cells, and high recovery of intact plasmid DNA from transfected cells.

Animals↗
PubMed1999

Distinctions between microglial cells and peripheral macrophages with regard to adhesive activities and morphology.

Activated microglial cells and peripheral macrophages are hardly distinguishable from the viewpoints of morphology and function. There are various immunological markers common to both microglial cells and peripheral macrophages. In the present study, however, we found that microglial cells have distinct characters in terms of adhesion and morphology. By using a "rheoscope," that is an apparatus to rheologically measure the strength of cell adhesion to substrates, rat microglial cells were found to attach to polystyrene dishes much more weakly than alveolar and peritoneal macrophages. Interferon-gamma (IFNgamma) strengthened the adhesion of alveolar and peritoneal macrophages, whereas it weakened that of microglial cells. Morphological changes of microglial cells induced by IFNgamma were also different from those of peripheral macrophages. Furthermore, alveolar and peritoneal macrophages produced NO in response to IFNgamma, while microglial cells did not. When cultured on astrocyte-derived extracellular matrix (AsECM) in serum-free medium, only microglial cells extended multiple ramified processes. Conversely, alveolar and peritoneal macrophages on AsECM shrunk their ruffling membrane and rounded up. These distinctions between microglial cells and macrophages may reflect differences in cell lineages as well as environments in which individual cells reside.

Animals↗
PubMed1999

S1319: a novel beta2-andrenoceptor agonist from a marine sponge Dysidea sp.

In the course of screening of potential leads for beta2-receptor agonists, we found a novel beta2-adrenoceptor selective agonist, S1319, from a marine sponge Dysidea sp. The active compound was isolated and structurally characterized as 4-hydroxy-7-[1-(1-hydroxy-2-methylamino)ethyl]-1,3-benzothiazole-2(3H)-o ne, a new member of the beta2-adrenoceptor agonist. This is the first example of a sponge-derived beta2-adrenoceptor agonist.

Adrenergic beta-2 Receptor Agonists↗
PubMed1999

Pentylenetetrazol-induced kindling stimulates the polyamine interconversion pathway in rat brain.

The levels of polyamines, N-acetylpolyamines, and GABA in the cerebral cortex and brainstem of rat brain after completion of pentylenetetrazol (PTZ)-induced kindling were investigated. Pretreatment with the polyamine oxidase inhibitor MDL72527 caused an accumulation of N1-acetylspermidine and N1-acetylspermine in normal rats. After a kindling seizure, the levels of N-acetylpolyamines were elevated, particularly in the cerebral cortex, indicating activation of polyamine interconversion. The levels of putrescine and GABA were lower in kindled rats pretreated with MDL72527. In addition, pretreatment with MDL72527 enhanced the seizure susceptibility to PTZ in normal rats. These results suggest that the polyamine interconversion pathway is involved in brain excitability, probably through the regulation of putrescine and GABA levels.

Animals↗
PubMed1999

Tracking the time course of object categorization using event-related potentials.

Object categorization processes were investigated by measuring event-related potentials while subjects categorized objects at the superordinate (e.g. animal), basic (e.g. dog) and subordinate (e.g. beagle) levels of abstraction. An enhanced negative deflection (N1) was found at posterior recording sites for subordinate level categorizations compared with basic level categorizations and was interpreted as a marker of increased visual analysis. In contrast, superordinate level categorizations produced a larger frontal negativity relative to basic level categorizations and were interpreted as an indicator of increased semantic processing. These results suggest a neurophysiological basis for the separate cognitive processes responsible for subordinate and superordinate object categorizations.

Adult↗
PubMed1999

Cell culture test of TCP/CPLA composite.

Thermoplastic polymers filled with a ceramic powder (here described as a "composite") of beta-tricalcium phosphate (TCP) and copoly-L-lactide (CPLA) was prepared by a heat-kneading method. The TCP/CPLA composite obtained had a three-point bending strength of 51.26 +/- 634 MPa, a Young's modulus of 5.18 +/- 1.11 GPa, and a fracture strength of 52.64 +/- 2.975 MPa, which is sufficient for usage as an artificial bone implant material. According to cell culture tests using MC3T3-E1 cells, the TCP/CPLA composite showed no cytotoxicity and the cells were in close contact with the surfaces of the composite without any observable morphological change. These results suggest that a composite consisting of osteoconductive TCP and biodegradable CPLA is suitable as a bioactive artificial bone material.

Absorbable Implants↗
PubMed1999

Composition and structure of the apatite formed on PET substrates in SBF modified with various ionic activity products.

An apatite layer was formed on polyethyleneterephthalate (PET) substrates by the following biomimetic process. PET substrates were placed on granular particles of a CaO-SiO2-based glass in simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma to form apatite nuclei on their surfaces (first treatment). They then were soaked in modified SBFs, the ion concentrations of which were changed to give a variation in ionic activity product of apatite (IP), in order to make the apatite nuclei grow (second treatment). The Ca/P atomic ratio and the lattice constant c of the formed apatite decreased from 1.54 to 1.40 and from 6.880 to 6.838 A, respectively, with increasing ion concentrations from 0.75 to 2.00 times those of SBF, that is, with increasing IP from 10(-96.6) to 10(-91.9). This was attributed to an increase in the concentration of HPO4(2-) ion substituting for the PO4(3-) ion sites, which gave an increase in the Ca2+ in the apatite. Even the apatite formed in 1.00 SBF showed a Ca/P ratio of 1.51 and lattice constants a of 9.432 A and c of 6.870 A. The Ca/P ratio and lattice constant c were smaller and the lattice constant a was larger than those of the bone apatite; its Ca/P ratio and its lattice constants a and c, were 1.65, 9.419 A, and 6.88 A, respectively. This was attributed to the lower content (2.64 wt%) of the CO3(2-) ion substituting for the PO4(3-) ion sites of the apatite compared to that of the bone apatite (5.80 wt%). The lower content of the CO3(2-) ion in the apatite might be caused by the lower concentration of HCO3- ion in 1.00 SBF compared to that in human blood plasma.

Apatites↗
PubMed1999

Astrocytes prevent neuronal death induced by reactive oxygen and nitrogen species.

Reactive oxygen and nitrogen species (RO/NS) such as nitric oxide (NO), hydroxyl radical (OH.), and superoxide anion (O(2)(-)) are generated in a variety of neuropathological processes and damage neurons. In the present study, we investigated the neuroprotective effects of rat astrocytes against RO/NS-induced damage using neuron-glia cocultures, and the effects were compared to those of microglial cells. Sodium nitroprusside (SNP), 3-morpholinosydnonimine (SIN-1), and FeSO(4) were used to generate NO, O(2)(-) and NO, and OH., respectively. Solely cultured neurons, which were transiently exposed to these agents, degenerated, possibly through apoptotic mechanisms as revealed by in situ detection of DNA fragmentation, whereas neurons cocultured with either astrocytes or microglial cells were viable even after exposure to RO/NS. In contrast, most neurons cocultured with meningeal fibroblasts degenerated. Astrocyte-conditioned medium partially attenuated RO/NS-induced neuronal damage. When neurons were cultured on astrocyte-derived extracellular matrix (AsECM), neuronal death induced by SNP and FeSO(4) was almost completely inhibited. AsECM contained significant amounts of laminin and fibronectin, and pure fibronectin and laminin also protected neurons against RO/NS-induced damage in the same manner as AsECM. These results suggest that astrocytes can protect neurons against RO/NS-induced damage by secreting soluble and insoluble factors.

Animals↗
PubMed1999

The application of immobilized polymyxin B fiber in the treatment of septic shock associated with severe acute pancreatitis: report of two cases.

The elimination of endotoxin by direct hemoperfusion over immobilized polymyxin B fiber (PMX-F) was carried out in two patients who developed septic shock associated with severe acute pancreatitis. Parameters such as blood pressure, body temperature, and plasma endotoxin level improved after PMX-F treatment, and the infected lesions were successfully and safely removed by surgery. Although an aggressive operative strategy of debridement with ultimate closure over drains is generally associated with low mortality in patients with this devastating disease, we often hesitate to perform this operation due to the poor condition of the patient in the acute period, with multiple organ failure and/or septic shock status, and also because of the difficulty in diagnosing the pancreatic infection. In this situation, endotoxin elimination using PMX-F is a useful tool for treating secondary pancreatic infections to help the patient recover in preparation for surgery, or for treating perioperative endotoxemia.

Acute Disease↗
PubMed1999

Screening for gastroenterological malignancies in new and maintenance dialysis patients.

To screen for gastroenterological malignancies in dialysis patients, we used the fecal occult blood test, examined the upper and lower gastrointestinal tract, and used abdominal ultrasonography in 178 patients starting dialysis (171 on hemodialysis and 7 on continuous ambulatory peritoneal dialysis (CAPD)) and 34 patients on maintenance dialysis (27 on hemodialysis and 7 on CAPD). Screening disclosed ten cancers (one esophageal cancer, three gastric cancers, four colorectal cancers, and two hepatocellular carcinomas) in 9 of the patients starting dialysis. Six cancers (one esophageal, three gastric, one colorectal, and one renal) were detected in 5 of the patients on maintenance dialysis. Since an increased incidence of malignancy has been reported in dialysis patients, gastroenterological screening appears to be worthwhile.

Abdomen↗
PubMed1999

The effect of cyclic AMP on expression of the major immediate-early genes and replication of human cytomegalovirus in human central nervous system cell lines.

The effect of dibutyryl cyclic AMP (dbcAMP) on interaction of human cytomegalovirus (HCMV) with human central nervous system cell lines was examined. Activation of the major immediate-early (IE) promoter (MIEP) of HCMV by dbcAMP was observed in human neuroblastoma IMR-32 cells, but not in glioma 118MGC and astrocytoma U373-MG cells. The 19 bp repeat element in the enhancer of the MIEP was most likely to be the cis-element that responded to dbcAMP in IMR-32 cells as we expected. In IMR-32 cells activation of the MIEP led to enhanced synthesis of the major IE proteins and infectious HCMV.

Astrocytoma↗
PubMed1999

Immunocytochemical localization of a cell adhesion molecule, integrin alpha5beta1, in nerve growth cones.

It is well-known that nerve growth cones, the growing tips of nerves, play a central role in determining the direction taken by regenerating peripheral nerves though neurotropism and contact guidance. In order to identify the molecules expressed on growth cones that are responsible for contact guidance, we investigated the possible involvement of integrins as sensors for the extracellular matrix. In cultured rat PC-12i cells and chick dorsal root ganglion cells, we found that integrin alpha5beta1 was concentrated in the filopodia and central regions of the growth cones. These integrin alpha5beta1-rich regions corresponded well with the sites where the growth cones came into contact with and adhered to the extracellular matrix. Integrin alpha5beta1 has been reported to bind with fibronectin in the extracellular matrix. When examined by triple staining and confocal laser scanning microscopy, we found that the distribution of integrin alpha5beta1 in the growth cones was very similar to that of actin filaments. Integrin alpha5beta1 was also expressed by Schwann cells. On immuno-electron microscopy, integrin alpha5beta1 was also identified in regenerating axons in vivo. These results suggest that integrin alpha5beta1 expressed on growth cones may function as a sensor for the extracellular matrix and Schwann cells, and thus mediate functionally important interactions in the development and regeneration of peripheral nerves.

Actin Cytoskeleton↗
PubMed1999

Orbitozygomatic approach by transposition of temporalis muscle and one-piece osteotomy.

BACKGROUND: A more simplified and easier technique for the orbitozygomatic approach is sought. We have developed a new modification to fully expose the temporal base before using one-piece craniotomy. METHODS: By transposing the temporalis muscle underneath the zygomatic arch before osteotomy, the temporal base and the inferior orbital fissure can be fully exposed. Craniotomy is made in one piece with the frontotemporal and orbitozygomatic bone together by using a high-speed drill. RESULTS AND CONCLUSIONS: Osteotomy was easy and the cosmetic result was satisfactory. This technique also allows better access to the subtemporal region without removing the zygomatic arch.

Craniotomy↗
PubMed1999

Effect of citric acid on the nucleation of hydroxyapatite in a simulated body fluid.

The role of citric acid in a simulated body fluid (SBF) was examined with the main focus on its induction ability of hydroxyapatite (HAp) nucleation on a bioinert collagen membrane. Collagen membranes were soaked in the SBF with citric acid concentrations in the range of 0-4 mM; then, carbonate-containing HAp crystals grew within a limited range, i.e., 0.3-2 mM. The results were explained in terms of chemical interaction among calcium ion, citric acid and collagen membrane, especially strong chelation ability of citric acid with the calcium ion.

Animals↗
PubMed1999

Morphological differentiation of microglial cells in culture: involvement of insoluble factors derived from astrocytes.

It is believed that ramified resting microglial cells in the brain are differentiated from macrophage-like ameboid cells, although the mechanism for the differentiation is not fully understood. In the present study, we investigated whether the differentiation of microglial cells is observable in mixed brain cell culture prepared from newborn rat forebrains. In confluent mixed brain cell culture, both ramified and ameboid microglial cells were simultaneously present. The ramified cells were located in or under the astrocyte monolayer, while the ameboid cells were over the layer as revealed by confocal laser scan microscopy. The majority of ramified cells appeared after the astrocyte layer was completely formed and they downregulated the expression of the major histocompatibility complex antigen. Fibronectin was detected around ramified microglial cells, and laminin was also present in the astrocyte monolayer in mixed brain cell culture, while both proteins were not distributed near ameboid cells over the monolayer. When purified microglial cells were cultured on astrocyte-derived extracellular matrix in serum-free medium, they ramified. These results show that the differentiation of microglial cells is observable in culture and that astrocytes may play pivotal roles in the differentiation mainly by secreting insoluble factors.

Animals↗