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Biomedical subjects

A Masuda

Publications and source records attributed to A Masuda.

At least 37 records · Page 2Linked to original sources
PubMed2001

Surface conduction on insulating BaTiO3 crystal suggesting an intrinsic surface electron layer.

We report conduction measurements on the clean, free surface of transparent insulating BaTiO3 single crystals in high vacuum. We find that the insulating BaTiO3 crystals exhibit surface conductance that is dependent on the spontaneous polarization, whereas no conduction perpendicular to the surface is observed. The surface conduction shows semimetallic temperature dependence and persists down to at least 100 K. The observations suggest a two-dimensional electron on a clean, free ferroelectric surface that may be regarded as a ferroelectric metal. The results have important implications for understandings of the fundamental properties of ferroelectrics, the size effect, and ferroelectric devices.

Journal Article↗
PubMed2001

Persistent increase in chromosome instability in lung cancer: possible indirect involvement of p53 inactivation.

Karyotype and fluorescence in situ hybridization analyses have demonstrated the frequent presence of an altered static state of the number of chromosomes (ie, aneuploidy) in lung cancer, but it has not been directly established whether aneuploidy is in fact associated with a persistent increase in the rate of chromosomal losses and gains (ie, chromosome instability, or CIN). The study presented here used a panel of 10 lung cancer cell lines to provide for the first time direct evidence that CIN is a common feature in lung cancer cell lines in association with the presence of significant aneuploidy. In addition, we found that the CIN phenotype correlates well with the presence of p53 mutations. However, human papilloma virus 16-E6-directed inactivation of p53 in a representative non-CIN lung cancer cell line did not result in the induction of CIN, at least up to the 25th generation, suggesting that inactivation of p53 itself is unlikely to directly induce CIN in lung cancer cells. Interestingly, however, significant CIN could be induced in conjunction with the generation of aneuploid populations when the mitotic spindle formation was transiently abrogated in p53-inactivated cells. These results suggest that inactivation of p53 may allow lung cancer cells to go through an inappropriate second division cycle under certain forms of mitotic stresses, which would result in the induction of the CIN phenotype in conjunction with the generation of aneuploidy.

Aneuploidy↗
PubMed2001

Protective function of p27(KIP1) against apoptosis in small cell lung cancer cells in unfavorable microenvironments.

A previous study of ours unexpectedly found that in contrast to frequent reductions in non-small cell lung cancer, high expression of the p27(KIP1) cyclin-dependent kinase (CDK) inhibitor was retained in virtually all small cell lung cancers (SCLCs), suggesting the possibility of high expression of nonfunctional p27(KIP1) in this virulent tumor. The study presented here, however, shows that p27(KIP1) in SCLC biochemically functions as a CDK inhibitor, clearly showing induction apparently associated with G(1)/G(0) arrest and efficient binding to and inhibition of the cyclin E-CDK2 complex. Interestingly, induction of p27(KIP1) seems to confer on SCLC cells the ability to survive under culture conditions unfavorable for cell growth such as a lack of nutrients and hypoxia. Subsequent experiments manipulating p27(KIP1) levels by using a sense p27(KIP1) expression construct or an antisense oligonucleotide supported this notion. These observations suggest that high expression of p27(KIP1) in vivo may favor the survival of SCLC by preventing apoptosis in a microenvironment unfavorable for cell proliferation.

Animals↗
PubMed2001

Lack of positive interaction between CO2 and hypoxic stimulation for P(CO2)-VAS response slope in humans.

To compare the effect of hypoxia on ventilatory responses and respiratory sensation to carbon dioxide, 29 young adults were examined using a modified Read's rebreathing method with four experimental conditions. We used varying gas mixtures and kept PET(O2) constant at >300, 100, 80 and 60 mmHg for each four rebreathing tests. Respiratory sensation was measured by visual analog scale (VAS). The slope of the CO2-ventilation response curve increased significantly with hypoxia, confirming a positive ventilatory interaction between hypoxia and hypercapnia. However, the slope of the CO2-VAS response curve remained unchanged. The V(E)-VAS relation slope tended to become depressed with advancing hypoxia, i.e. the magnitude of VAS elicited by a given ventilation decreased with hypoxia, signifying that dyspneic sensation was effectively mitigated during hypoxic hyperventilation. We suggest that this relief of dyspneic sensation might be due to the inhibitory respiratory effect from augmented pulmonary stretch receptor (PSR) activity.

Adult↗
PubMed2001

Two new pyrrolidine alkaloids, radicamines A and B, as inhibitors of alpha-glucosidase from Lobelia chinensis Lour.

Two new pyrrolidine alkaloids, radicamines A and B were isolated as inhibitors of alpha-glucosidase from Lobelia chinensis Lour. (Campanulaceae). Radicamines A and B were formulated as (2S,3S,4S,5S)-2-hydroxymethyl-3,4-dihydroxy-5-(3-hydroxy-4-methoxyphenyl)-pyrrolidine (1) and (2S,3S,4S,5S)-2-hydroxymethyl-3,4-dihydroxy-5-(4-hydroxyphenyl)-pyrrolidine (2) on the basis of spectroscopic analyses and chemical methods.

Asia↗
PubMed2001

Attachment of Malassezia pachydermatis to the ear dermal cells in canine otitis externa.

To investigate the predominance of Malassezia pachydermatis (M. pachydermatis) as a causative agent of canine otitis externa, ear cerumen samples were observed for adhesion of M. pachydermatis to the cornified epithelial cells by light and electron microscopes. The yeasts appeared not to adhere to the cornified epithelial cells directly, but they seemed to exist in the proximity of the epithelial cells with an electron opaque halo-like space around them. Polysaccharide and lipid staining techniques were conducted to identify the substances existing in that space. Lipid substances, not saccharides, were observed around the yeasts and the cornified epithelial cells. These results suggested that in the canine ear canal malassezia yeast attachment to the cornified epithelial cells is mediated by lipids.

Animals↗
PubMed2001

Brief functional analysis and treatment of bizarre vocalizations in an adult with schizophrenia.

Variables responsible for the maintenance of bizarre vocalizations emitted by an adult diagnosed with schizophrenia were examined via a brief functional analysis, and results suggested that the behavior was maintained by attention. A treatment consisting of extinction and differential reinforcement of appropriate vocalizations was effective in reducing bizarre vocalizations and increasing appropriate vocalizations. The use of functional analysis methodology to examine variables that maintain problem behavior in this population is discussed.

Adult↗
PubMed2001

Cognitive behavioral therapy and fasting therapy for a patient with chronic fatigue syndrome.

Cognitive behavioral therapy temporarily alleviated symptoms of a chronic fatigue syndrome patient but the anxiety about rehabilitation into work became stronger and his symptoms worsened. This patient was successfully rehabilitated by fasting therapy. Natural killer cell activity and serum acylcarnitine levels recovered after fasting therapy. Though fasting therapy transiently increased physical and mental subjective symptoms, the patient gained self-confidence by overcoming difficulties after fasting therapy. A combination of cognitive behavioral therapy and fasting therapy is promising as a treatment for chronic fatigue syndrome.

Adult↗
PubMed2001

Hyperbaric oxygen for anorexia nervosa.

Hyperbaric oxygen was given to a patient with anorexia nervosa who had developed postoperative ileus, resulting in not only improvement in ileus, but also enhancement of intestinal movement, inducing the feeling of hunger, and thereby increasing food ingestion. Hyperbaric oxygen may be effective as an initial treatment for anorectic patients showing severe bloating and resistance to food ingestion.

Adolescent↗
PubMed2001

Hearing restoration from deafness after resection of a large cerebellopontine angle meningioma--case report.

A 61-year-old man presented with a large cerebellopontine angle meningioma manifesting as a 1-year history of deafness on the right side, in whom hearing was restored from the deaf state immediately after tumor resection. Neuroimaging demonstrated a large mass in the right cerebellopontine angle, originating at the region adjacent to the jugular foramen. Audiometry showed his hearing was off-scale (> 105 dB) on the right. The tumor was successfully removed through the retrosigmoid approach, and the integrity of the 7th and 8th cranial nerves was maintained. The patient regained hearing on the day after the operation, which continued to improve until near-normal. The 8th cranial nerve function may recover dramatically after removal of non-acoustic tumors, even if preoperative hearing loss is profound. To maximize the opportunity to regain hearing, approaches which devastate cochlear function should be avoided and more meticulous manipulation during tumor removal is needed.

Audiometry, Pure-Tone↗
PubMed2001

Advanced bladder cancer in a young female: a case report.

We present a rare case of advanced bladder cancer in a young female. A 27-year-old woman had the chief complaint of proteinuria. A clinical examination revealed a papillary, broad-based bladder tumor with a clinical stage of T3, N3, M0. Preoperatively, 3 courses of neoadjuvant chemotherapy with methotrexate, adriamycin, and cisplatin were performed, and proved to be effective. Radical cystectomy was done and the histopathologically it was diagnosis as Grade 2 transitional cell carcinoma, which did not show any p53 gene mutation. The patient's postoperative clinical course was uneventful, and she remained disease free for 27 months. Bladder carcinoma in patients under 30 years of age tends to have a early stage and a low grade. However, the above described 27-year-old female patient demonstrated the advanced stage bladder tumor. Therefore, it should be kept in mind to accurately evaluate young patients with transitional cell carcinoma of the bladder and not to rule out the possibility of advanced disease even though a patient is young.

Adult↗
PubMed2000

In vitro assessment of Metarhizium anisopliae isolates to control the cattle tick Boophilus microplus.

Metarhizium anisopliae is a filamentous fungus used for tick control. The in vitro effects of 12 M. anisopliae isolates on engorged Boophilus microplus females were analysed. The most pathogenic isolate (E6S1) caused a 100% death rate when 10(7) spores/ml were used to infect ticks. Isolates of M. anisopliae taken from experimentally infected ticks proved to be more pathogenic than fungus maintained on culture media. A comparison between dsRNA mycovirus-free and infected M. anisopliae isolates suggested that, in general, virus free isolates were more infective. The results showed that the biological control of B. microplus by M. anisopliae infection might constitute an additional method to integrated tick control management.

Animals↗
PubMed2000

Cutting edge: naturally occurring soluble form of mouse Toll-like receptor 4 inhibits lipopolysaccharide signaling.

Toll-like receptors (TLRs) are a family of proteins playing important roles in host defense. Mice defective of functional TLR4 are hyporesponsive to LPS, suggesting that TLR4 is essential for LPS signaling. Here we report the cloning of an alternatively spliced mouse TLR4 (mTLR4) mRNA. The additional exon exists between the second and third exon of the reported mTLR4 gene and contains an in-frame stop codon. The alternatively spliced mRNA encodes 86 aa of the reported mTLR4 and an additional 36 aa. This alternatively spliced mTLR4 mRNA expressed a partially secretary 20-kDa protein, which we named soluble mTLR4 (smTLR4). In a mouse macrophage cell line, the exogenously expressed smTLR4 significantly inhibited LPS-mediated TNF-alpha production and NF-kappaB activation. Additionally, in mouse macrophages, LPS increased the mRNA for smTLR4. Taken together, our results indicate that smTLR4 may function as a feedback mechanism to inhibit the excessive LPS responses in mouse macrophages.

Alternative Splicing↗
PubMed2000

Synthesis of derivatives of NK109, 7-OH benzo[c]phenanthridine alkaloid, and evaluation of their cytotoxicities and reduction-resistant properties.

The N5-C6 double bond of NK109 (an antitumor benzo[c]phenanthridine alkaloid) is easily reduced under biological environment. To suppress the inactivation caused by reduction, we synthesized 5-, 6-, and 8-substituted NK109. 5-Substituted derivatives (4a-c) were reduced more easily than NK109. 6-Substituted ones (10a-f) inhibited biological reduction, but showed weak cytotoxic activity. 8-O-Substituted ones (13a-h), especially 8-O-hydroxyethyl NK109 (13d), suppressed biological reduction and exhibited strong cytotoxic activity.

Antineoplastic Agents↗
PubMed2000

Interleukin-15 induces rapid tyrosine phosphorylation of STAT6 and the expression of interleukin-4 in mouse mast cells.

Interleukin (IL)-4 plays an important role in the differentiation of naive T helper (Th) cells into Th2. Mast cells can produce a significant amount of IL-4 and have been proposed to play a major role in the induction of Th2 responses. Recently, it has been reported that mast cells have a distinct IL-15 receptor system different from that of T or natural killer cells. In the present study, we demonstrated that IL-15 induced IL-4 production from a mouse mast cell line, MC/9, and bone marrow-derived mast cells. IL-4 mRNA expression was increased by IL-15, suggesting that IL-15 promotes IL-4 expression at the transcriptional level. In these mast cells, signal transducer and activator of transcription (STAT) 6 were rapidly tyrosine-phosphorylated in response to IL-15. In MC/9 cells, the expression of a C-terminally truncated dominant negative form of STAT6 significantly suppressed the IL-4 mRNA up-regulation by IL-15, suggesting that STAT6 activation is essential for the IL-15-mediated IL-4 production. Additionally, tyrosine phosphorylation of Tyk2 was rapidly increased by IL-15 treatment in this cell line. Altogether, our results suggest that IL-15 plays an important role in stimulating early IL-4 production in mast cells that may be responsible for the initiation of Th2 response.

Animals↗