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Biomedical subjects

H Ikeda

Publications and source records attributed to H Ikeda.

At least 397 records · Page 22Linked to original sources
PubMed1998

Temperature-induced momentum-dependent spectral weight transfer in Bi2Sr2CaCu2O8+delta

Angle-resolved photoemission data from the cuprate superconductor Bi2Sr2CaCu2O8+delta above and below the superconducting transition temperature Tc reveal momentum-dependent changes that extend up to an energy of about 0.3 electron volt, or 40kTc (where k is the Boltzmann constant). The data suggest an anomalous transfer of spectral weight from one momentum to another, involving a sizable momentum transfer Q approximately (0.45pi, 0). The observed Q is intriguingly near the charge-order periodicity required if fluctuating charge stripes are present.

Journal Article↗
PubMed1998

Immunological assessment of the distribution of type VII adenylyl cyclase in brain.

The localization of the nine identified isoforms of adenylyl cyclase in brain has been largely based on determination of patterns of mRNA expression. A polyclonal antibody has now been developed that specifically recognizes Type VII adenylyl cyclase. This antibody was used for immunocytochemical analysis of the distribution of Type VII adenylyl cyclase in rat brain. Labeling of Type VII adenylyl cyclase was observed in several areas, including cerebellum, caudate-putamen, nucleus accumbens, hippocampus and cerebral cortex. In some of these areas, the staining of the adenylyl cyclase protein suggested the possibility of presynaptic localization. For example, in situ hybridization showed Type VII adenylyl cyclase mRNA concentrated in cerebellar granule neurons. The cerebellar granule cell layer, however, showed little immunostaining, while punctate immunostaining was observed in the molecular layer. These results suggested that protein synthesized in the granule neurons may be targeted to the neuron terminals. Punctate staining in the caudate-putamen, globus pallidus and nucleus accumbens also suggested the possibility of axonal and/or dendritic localization of Type VII adenylyl cyclase in these regions. Labeling of the soma of cerebellar Purkinje cells, cortical pyramidal and non-pyramidal cells and interneurons in the cerebellum and hippocampus was also observed. Type VII adenylyl cyclase, like the other adenylyl cyclase isoforms, has distinct regulatory characteristics, including sensitivity to stimulation by Gsalpha and G protein betagamma subunits, modulation by protein kinase C, and high sensitivity to stimulation by ethanol. These characteristics, and the discrete localization of this enzyme, may contribute to its ability to provide signal integration and/or control of neurotransmitter release in particular neurons or brain areas.

Adenylyl Cyclases↗
PubMed1998

Reirradiation of brain and skull base tumors with fractionated stereotactic radiotherapy.

PURPOSE: We evaluated the feasibility of fractionated stereotactic radiotherapy for small intracranial recurrences after conventional radiotherapy. METHODS AND MATERIALS: Nineteen patients who had initially undergone conventional radiotherapy to intracranial lesions, receiving a median total dose of 50 Gy in 5 weeks, were retreated with stereotactic radiotherapy for their recurrences and received a median total dose of 42 Gy in seven fractions over 2.3 weeks. RESULTS: Of the 19 patients, 15 achieved local control 3-51 months after reirradiation. No patient suffered from acute reaction, but one patient with a history of extensive radiotherapy developed progressive radionecrosis 9 months after reirradiation. CONCLUSIONS: Fractionated stereotactic radiotherapy of intracranial recurrences appears to be effective in achieving in local control with negligible morbidity. We believe it merits further investigation in a prospective study.

Adult↗
PubMed1998

Cloning of the gene encoding avermectin B 5-O-methyltransferase in avermectin-producing Streptomyces avermitilis.

Complementation of a mutant lacking avermectin B 5-O-methyltransferase (AveD) of Streptomyces avermitilis, which catalyses the methylation of the hydroxyl group at the C5 position of avermectin B compounds, revealed that the gene encoding AveD is in a 1.25-kb SalI-EcoNI fragment in the left region of the gene cluster for avermectin biosynthesis. The nucleotide sequence of this fragment predicted a 283-aa gene product homologous to several methyltransferases requiring S-adenosyl-l-methionine as a cofactor. After cloning of the aveD region from mutant not producing AveD, the complementation experiments were performed using a pair of hybrid fragments (AveD+/AveD- and AveD-/AveD+). They suggest that the mutation(s) is in the N-terminus of AveD. SSCP analysis of amplified DNA of the aveD region derived from both wild type and mutant strains supports the results of the complementation experiments. Sequence analysis of the aveD region of the mutant strain revealed that a point mutation is within ORF, being Thr23-->Ile substitution. This mutation causes the inactivation of O-methyltransferase activity of AveD.

Amino Acid Sequence↗
PubMed1998

Gamma knife radiosurgery for pituitary adenomas: usefulness of combined transsphenoidal and gamma knife radiosurgery for adenomas invading the cavernous sinus.

Thirty-seven of 317 patients with pituitary adenoma who underwent transsphenoidal operation from 1989 to 1996 received adjuvant gamma knife radiosurgery. Gamma knife surgery was performed mainly in patients with endocrinologically inactive tumor for tumor regrowth invading the cavernous sinus, and in patients with endocrinologically active tumor for incomplete removal invading the cavernous sinus. The maximum radiation dose was 25-60 Gy. The periphery of the tumor usually received 50% of the maximum dose. Thirteen patients were followed up for longer than 2 years (mean 45 months) after combined therapy. Magnetic resonance imaging (MRI) showed changes in signal intensity on both T1- and T2-weighted images as early as 3 months after radiotherapy. Serial MRI showed all 13 patients had achieved excellent response. Patients with endocrinologically active tumors showed normalized hormone levels 24 months after gamma knife surgery except for one patient with acromegaly. The basal value of pituitary hormones remained normal during the follow-up period, and four female patients became pregnant without hormonal therapy. Combined transsphenoidal surgery and gamma knife radiosurgery can preserve normal pituitary function and eradicate adenoma invading the cavernous sinus.

Adenoma↗
PubMed1998

Pioglitazone time-dependently reduces tumour necrosis factor-alpha level in muscle and improves metabolic abnormalities in Wistar fatty rats.

In order to evaluate the relationship between tumour necrosis factor-alpha (TNF-alpha) level in muscle and metabolic abnormalities in obesity and diabetes mellitus, pioglitazone, a novel insulin-sensitizing agent, was administered to Wistar fatty rats and time-dependent changes in muscle TNF-alpha content and plasma indicators of diabetes and obesity were measured. Wistar fatty rats were hyperglycaemic, hyperlipidaemic and hyperinsulinaemic, and their plasma and muscle TNF-alpha levels were two or more times higher than those in normal lean rats at 16 weeks of age. When pioglitazone was administered to fatty rats at a dose of 3 mg kg(-1) day(-1), the plasma triglyceride level and TNF-alpha levels in plasma and muscle decreased time-dependently, and reached the levels of lean rats within 4 days. Plasma glucose and insulin levels also decreased time-dependently with pioglitazone, but on day 4, these levels were still much higher than the levels in lean rats. Neutral sphingomyelinase (SMase) activity in muscle of fatty rats was two times higher than that in lean rats and was lowered to the level of that in lean rats by 4 days' pioglitazone administration. The plasma leptin level in fatty rats was 8 times higher than that in lean rats, but pioglitazone did not affect the level during the 4-day administration period. These results suggest that an increase in TNF-alpha production and subsequent activation of SMase in muscle leads to metabolic abnormalities in obesity and diabetes and that antidiabetic activity of pioglitazone is deeply associated with the suppression of TNF-alpha production.

Animals↗
PubMed1998

Hemorrhage in pituitary adenoma: correlation of MR imaging with operative findings.

The aim of this study was to correlate MR imaging and operative findings of hemorrhage in pituitary macroadenomas. We retrospectively reviewed MR images of 113 surgically proven pituitary adenomas. All patients were examined on a 1.5-T MR system. The intensity of intratumoral cystic cavities was correlated with operative findings. In 15 patients with pituitary apoplexy, we determined relationship between interval of MR examination after apoplectic event and MR signal intensity. In 8 patients with repeated preoperative MR examination, we evaluated sequential changes of intratumoral hemorrhage. There were 54 cavities at surgery: 52 were hemorrhagic and 2 were nonhemorrhagic. Twenty-nine of 52 hemorrhagic cysts demonstrated high/low signal (H/L) fluid-fluid levels on T2-weighted image (T2WI). In 19 of them, two components could be separately seen at operation: the supernatant high-intensity area represented xanthochromic fluid, and the dependent low-intensity area represented liquefied hematoma. The H/L fluid-fluid level was observed predominantly in hematomas on MR images obtained after longer intervals. In patients with repeated MR examination, follow-up MR imaging revealed additional hemorrhage or new formation of fluid-fluid levels. It was surprising that 12 of 14 cysts preoperatively judged as nonhemorrhagic in fact contained hemorrhagic components. The preoperative MR images are well correlated to the operative findings in hemorrhagic pituitary macroadenomas. It proved that 52 of 54 cystic cavities had hemorrhagic component.

Adenoma↗
PubMed1998

Multiple sulphatase deficiency and haemophagocytic syndrome.

A 3-year-old boy with multiple sulphatase deficiency, complicated by a haemophagocytic syndrome, recovered with conventional treatment. Haemophagocytic syndrome can be a complication of many disorders including metabolic diseases, frequently triggered by intracellular viral and bacterial infections or even by drug administration.

Child, Preschool↗
PubMed1998

The RHC21 gene of budding yeast, a homologue of the fission yeast rad21+ gene, is essential for chromosome segregation.

The Saccharomyces cerevisiae gene RHC21 is a homologue of the fission yeast rad21+ gene, which affects the sensitivity of cells to gamma-irradiation and is essential for cell growth in S. pombe. Disruption of the RHC21 gene showed that it is also essential in S. cerevisiae. To examine its function in cell growth further, we have isolated temperature-sensitive mutants for the RHC21 gene and characterized one of them, termed rhc21-sk16. When this mutant was incubated at 36 degrees C, the percentage of large-budded cells was increased. Most of the large-budded cells had aberrant nuclear structures, such as unequally extended nuclear DNA with incompletely elongated spindles across the mother-daughter neck or only in a mother cell. Furthermore, a circular minichromosome is more unstable in the mutant than in the wild-type, even at 25 degrees C. Flow cytometry showed that the bulk of DNA replication takes place normally at the restrictive temperature in the mutant. These results indicated that the RHC21 gene is required for proper segregation of the chromosomes. In addition, we found that the mutant is sensitive not only to UV radiation and gamma-rays but also to the antimicrotubule agent nocodazole at 25 degrees C. This suggests that the RHC21 gene is involved in the microtubule function. We discuss how the RHC21 gene product may be involved in chromosome segregation and microtubule function.

Cell Cycle Proteins↗
PubMed1998

Novel mutations of the peripheral myelin protein 22 gene in two pedigrees with Dejerine-Sottas disease.

Peripheral myelin protein 22 (PMP22), a membrane glycoprotein, plays a significant role in the formation and/or maintenance of compact myelin in the peripheral nervous system. We studied two pedigrees with Dejerine-Sottas disease and identified two novel mutations in the PMP22 gene: one a 2-bp deletional mutation at nucleotide positions 426 and 427 of exon 4 (this is predicted to alter the reading frame at leucine 80 and thus to lead to frame-shifted translation), and the other a guanine to thymine substitution at nucleotide position 636 leading to a cysteine substitution for glycine 150. Both mutations were located in the putative transmembrane domains reported in many cases of Charcot-Marie-Tooth neuropathy, Dejerine-Sottas disease, and hereditary neuropathy with liability to pressure palsies. The results suggest an important role for the putative transmembrane domains of PMP22 in its function.

Adult↗
PubMed1998

Oxidative stress is related to exercise intolerance in patients with heart failure.

To assess the role of oxidative stress in exercise intolerance in patients with heart failure, a symptom-limited exercise test was performed with a bicycle ergometer in 12 patients with heart failure and in 7 members of a healthy control group. Level of plasma malondialdehyde, a marker of lipid peroxidation, at rest was significantly higher in patients than in the control group. The level further increased at peak exercise in patients but not in the control group. A significant inverse correlation was observed in patients between exercise-induced changes in malondialdehyde level and erythrocyte superoxide dismutase activity (r = -0.73, p < 0.01), and those exercise-induced changes in malondialdehyde level and superoxide dismutase activity had a close correlation with peak VO2 (r = -0.63, p < 0.05 and r = 0.67, p < 0.05, respectively), whereas no such correlation was observed in the control group. These findings suggest that the oxidative stress could be related to exercise intolerance in patients with heart failure.

Adult↗
PubMed1998

Intra-coronary administration of L-arginine aggravates myocardial stunning through production of peroxynitrite in dogs.

OBJECTIVE: The aim of this study was to investigate how the enhanced nitric oxide (NO) production by intra-coronary infusion of L-arginine acts in myocardial stunning in dogs by focusing on the involvement of peroxynitrite, a reaction product of NO and superoxide anion. METHODS AND RESULTS: Dogs were divided into six groups; a control non-treated group (CON, n = 9), and NG-nitro L-arginine methyl ester (L-NAME, n = 6), 1 mM L-arginine (L-ARG, n = 8), D-arginine (D-ARG, n = 6), L-arginine plus superoxide dismutase (L-ARG + SOD, n = 6), and SOD alone (SOD, n = 6) treated groups. L-NAME, or L- or D-arginine was continuously infused into the left anterior descending coronary artery (LAD) starting just prior to reperfusion, whereas SOD was intravenously injected before occlusion. During 120 min of reperfusion after 15 min occlusion of LAD, myocardial contractile function in the ischemic region gradually recovered and reached approximately 70% of the preischemic level in CON, D-ARG and SOD, but it remained dyskinetic (-46%) in L-ARG. On the other hand, it was improved in L-NAME (90%). Tissue malondialdehyde was elevated (p < 0.005) after reperfusion, and myocardial NO metabolites measured by an intratissue-microdialyzer increased (approximately 150%, p < 0.05) in the ischemic region during reperfusion in L-ARG but not in the CON, L-NAME, D-ARG or SOD groups. In the L-ARG + SOD group, L-arginine-induced contractile dysfunction and elevation of malondialdehyde were prevented, but the increase in NO metabolites remained. These results suggest that L-arginine aggravated myocardial stunning through oxidative stress and the cytotoxicity was caused by NO derivatives but not by NO itself. The formation of nitrotyrosine, a footprint of peroxynitrite, was immunohistochemically confirmed in the ischemic region of L-ARG. CONCLUSIONS: Our results demonstrate for the first time in vivo that NO has a detrimental role in myocardial stunning through the production of peroxynitrite.

Analysis of Variance↗
PubMed1998

Surgical treatment of neuroblastomas in infants under 12 months of age.

BACKGROUND: Surgical treatment of neuroblastomas, both those detected by screening and those detected clinically, in infants less than 12 months of age, is controversial, because some tumors in this age group potentially have the ability to regress spontaneously. METHODS: From January 1985 to March 1997, the authors treated 50 infants (under 1 year of age) with neuroblastoma: 23 boys and 27 girls. Forty-one cases were detected preclinically by screening when the patients were 6 to 11 months of age (median, 7 months), and nine patients were discovered to have clinical manifestations at the age of 1 to 10 months (median, 4 months). RESULTS: The tumor was INSS stage 3 or 4 in 10 patients (24%) with screening-detected tumor and in five (56%) with clinically detected tumor, although the difference was not statistically significant. Four screening-positive patients had multifocal primary tumors, and three of them were synchronous bilateral adrenal neuroblastomas. There was no statistically significant difference between the screening-detected tumors and the clinically detected tumors in biological characteristics such as Shimada's histology, DNA ploidy, and N-myc amplification. Complete resection of the primary lesion was accomplished by either primary surgery or second look (delayed primary) surgery in 46 patients (92%), and the resection was incomplete in the remaining four. In patients with bilateral adrenal tumors, the larger one was primarily resected, and the smaller contralateral tumor was enucleated or resected by partial adrenalectomy. Surgical complications included postoperative adhesive ileus (n=2), Horner's syndrome (n=2), renal atrophy (n=1), renal failure (n=1), phrenic nerve injury (n=1), chylous ascites (n=1), chylothorax (n=1) and intussusception (n=1). One patient died of respiratory failure caused by a complication, but 49 patients (98%) were alive at the time of evaluation. CONCLUSION: When considering surgical treatment of infants with biologically favorable neuroblastoma, the risk involved in treatment should be weighed against the risk inherent in a tumor capable of spontaneous regression, and aggressive surgery is unacceptable.

Adrenal Gland Neoplasms↗
PubMed1998

Prenatally diagnosed cystic lymphangioma in infants.

BACKGROUND/PURPOSE: Prenatally diagnosed cystic lymphangioma (CL) is often associated with chromosomal anomalies, hydrops fetalis, and, in the case of cervical CL, occasionally respiratory distress just after birth. Often it is difficult to treat prenatally diagnosed CL because of the large size and associated symptoms. METHODS: Between 1988 and 1997, 11 cases of prenatally diagnosed CL were treated. Five pregnancies were terminated electively and one aborted spontaneously (nondelivered, non-D group), and another five delivered (delivered, D group). Thirteen infants nondiagnosed prenatally were also seen in the same period (prenatally nondiagnosed, without pre-D group). RESULTS: In the non-D group, massive CLs were diagnosed by ultrasound scan between 16 and 20 weeks' gestation. They occurred in the head and neck in all six cases, and four had associated pleural effusions or hydrops. In the D group, CL occurred in the face and neck in four cases. Three were born by cesarean section with neonatologists and surgeons standing by, then transferred to our hospital immediately after birth. Respiratory distress appeared in two cases; tracheostomy was carried out in one case. One patient with a huge CL in the chest and abdominal wall necessitated partial resection after OK-432 sclerotherapy. In the without pre-D group, there was CL in the face or neck in 10 cases, abdominal wall in two cases, and chest wall in one case. Respiratory distress was observed in three cases of cervical CL, and tracheostomy was required in two cases. One patient with hypoxic brain damage sequela died of pneumonia afterward. CONCLUSIONS: Prenatal diagnosis permits planned delivery, prompt postnatal resuscitation, and improve prognosis. Infants with massive CL diagnosed early in pregnancy have other associated anomalies as well as hydrops fetalis, and a poor outcome or difficult management can be expected.

Diagnosis, Differential↗
PubMed1998

EGG phosphatidylcholine combined with vitamin B12 improved memory impairment following lesioning of nucleus basalis in rats.

We investigated the effects of egg phosphatidylcholine (PC) combined with vitamin B12 on memory in the Morris water maze task, and on choline and acetylcholine (ACh) concentrations in the brain of rats. Animals with nucleus basalis Magnocellularis (NBM) lesion received intragastric administration of egg PC or vitamin B12, or both for 18 days. Memory acquisition and retention were remarkably impaired in NBM lesioned rats compared with in sham-operated control. NBM lesioned group had lower choline and ACh concentrations than control group in the frontal cortex. High dose of egg PC alone significantly increased choline concentration, but did not change ACh concentration in the frontal cortex. High dose of vitamin B12 alone did not change choline and ACh concentrations in the brain. Either egg PC or vitamin B12 did not improve memory acquisition and retention. However, low dose of egg PC combined with vitamin B12 significantly increased ACh concentration and improved memory acquisition and retention in the NBM lesioned rats. We concluded that egg PC combined with vitamin B12 improved the memory impairment of NBM lesioned rats through the action on the cholinergic neurons.

Acetylcholine↗
PubMed1998

Heat-killed Lactobacillus plantarum L-137 suppresses naturally fed antigen-specific IgE production by stimulation of IL-12 production in mice.

BACKGROUND: Food allergy is caused by production of IgE against dietary antigen induced by T(H2) response. IL-12 inhibits T(H2) responses and strongly suppresses IgE production. We have recently established a murine model for IgE production with a predominant T(H2) response induced by feeding antigen. OBJECTIVE: We here show a suppressive effect of heat-killed Lactobacillus plantarum L-137, a potent inducer of IL-12, on IgE production against naturally fed antigen in a murine model. METHODS: The ability of L. plantarum L-137 to induce IL-12 production was examined in vitro and in vivo. DBA/2 mice were fed a casein diet and injected intraperitoneally with L. plantarum L-137 from the beginning of feeding or 2 weeks later. Recombinant mouse IL-12 was also injected 2 weeks after the start of feeding. Casein-specific IgE and IgG1 in plasma were determined by ELISA. RESULTS: L. plantarum L-137 directly induced IL-12 production by the peritoneal macrophages and also stimulated spleen cells to produce both IL-12 and interferon-gamma in vitro. In vivo treatment of L. plantarum L-137 also increased the plasma level of IL-12 in mice. Plasma anti-casein IgG1 and IgE levels were gradually elevated in DBA/2 mice fed a casein diet. Administration of L. plantarum L-137 from the beginning of feeding suppressed the elevation of anti-casein IgE levels, whereas the levels of anti-casein IgG1 were rather augmented by L. plantarum L-137. IL-12 production of the peritoneal macrophages was enhanced, but IL-4 production of concanavalin A (Con A)-stimulated spleen cells was suppressed in the L. plantarum L-137-treated mice compared with control mice fed a casein diet. When L. plantarum L-137 was given from 2 weeks after the start of feeding, anti-casein IgE levels were also significantly suppressed, which was similar to the result found in mice treated with IL-12. CONCLUSION: Our results suggest that L. plantarum L-137, a potent IL-12 inducer, is useful for prevention and treatment of food allergy.

Animals↗