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Biomedical subjects

K Yamanaka

Publications and source records attributed to K Yamanaka.

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

Multiple thymoma with myotonic dystrophy.

A case of multiple thymoma associated with myotonic dystrophy is reported. The patient was a 42-year-old man who had two separate encapsulated thymoma in the anterior mediastinum, at 3 cm in diameter on the right side, and at 4 cm in diameter on the left. Extended thymo-thymomectomy was performed. Microscopically, the tumor in the right thymic lobe was predominantly mixed type, and that in the left predominantly epithelial type. Neuromuscular disease appeared to develop, with severe sputum retention in the larynx and he was referred to neurology at 6 months after surgery. On examination, he presented a characteristic hatchet face, muscle atrophy, muscle weakness, percussion myotonia and grip myotonia, and diagnosis was revised to be multiple thymoma associated with myotonic dystrophy. This association is extremely rare. It is difficult to clarify whether this association was a syndrome or coincidence.

Adult↗
PubMed2001

Theoretical studies of the ATP hydrolysis mechanism of myosin.

The ATP hydrolysis mechanism of myosin was studied using quantum chemical (QM) and molecular dynamics calculations. The initial model compound for QM calculations was constructed on the basis of the energy-minimized structure of the myosin(S1dc)-ATP complex, which was determined by molecular mechanics calculations. The result of QM calculations suggested that the ATP hydrolysis mechanism of myosin consists of a single elementary reaction in which a water molecule nucleophilically attacked gamma-phosphorus of ATP. In addition, we performed molecular dynamics simulations of the initial and final states of the ATP hydrolysis reaction, that is, the myosin-ATP and myosin-ADP.Pi complexes. These calculations revealed roles of several amino acid residues (Lys185, Thr186, Ser237, Arg238, and Glu459) in the ATPase pocket. Lys185 maintains the conformation of beta- and gamma-phosphate groups of ATP by forming the hydrogen bonds. Thr186 and Ser237 are coordinated to a Mg(2+) ion, which interacts with the phosphates of ATP and therefore contributes to the stabilization of the ATP structure. Arg238 and Glu459, which consisted of the gate of the ATPase pocket, retain the water molecule acting on the hydrolysis at the appropriate position for initiating the hydrolysis.

Adenosine Diphosphate↗
PubMed2001

Two-staged gamma knife radiosurgery for the treatment of large petroclival and cavernous sinus meningiomas.

BACKGROUND: In this study, we report on the effectiveness and usefulness of two-staged gamma knife radiosurgery (GKS) for large petroclival and cavernous sinus meningiomas that have a high rate of surgical morbidity. METHODS: We have treated 7 patients suffering from large petroclival and cavernous sinus meningiomas using two-staged radiosurgery since March 1995. The tumors were located in the petroclival region in 4 patients, the cavernous sinus region in 2 patients, and in the petrocavernous region in the remaining patient. Three of the patients had been surgically treated and 4 patients (57%) were only followed with MR imaging. The volume of the tumors ranged between 34.5 to 101 cm(3) (mean 53.5 cm(3)). The treatment volume was between 6.8 to 29.6 cm(3) (mean 18.6 cm(3)). The treatment interval between the first GKS and second GKS was 6 months. The marginal doses for the tumors were 8 to 12 Gy (mean, 9 Gy). RESULTS: Six patients demonstrated tumor growth control during the follow-up period after the first radiosurgery (mean 39 months). Tumor regression was observed in 3 patients (43%). Three patients (43%) had improved clinically by the time of the follow-up examinations. No patient suffered from symptomatic radiation injury. CONCLUSION: Although we have treated only 7 patients using two-staged GKS, we believe this treatment may be a very useful option for large petroclival and cavernous sinus meningiomas in selected patients.

Aged↗
PubMed2001

An anatomic study of the extensor tendons of the human hand.

A total of 548 upper limbs (276 right and 272 left hands) from Japanese cadavers were dissected. The arrangements of extensor indicis proprius, extensor digitorum communis (EDC), and extensor digiti minimi tendons and the intertendinous connections were studied. The most common pattern of extensor tendons was as follows: the index finger had a single EDC tendon, the middle finger had a single EDC tendon, the ring finger had a single EDC tendon, and the small finger had a single EDC tendon or a single common EDC tendon distributed to the ring and small finger. A single extensor indicis proprius tendon ran along the ulnar side of the EDC, and the extensor digiti minimi tendon consisted of 2 slips. Intertendinous connections were classified into 3 types: type 1 with a filamentous band, type 2 with a fibrous band, and type 3 with a tendinous band subdivided to r-shaped and y-shaped. The most common patterns were type 1 in the second intermetacarpal space (IMCS), type 3r in the third IMCS, and type 3y in the fourth IMCS.

Cadaver↗
PubMed2001

Induction of CspA, an E. coli major cold-shock protein, upon nutritional upshift at 37 degrees C.

BACKGROUND: The synthesis of CspA, the major cold-shock protein of Escherichia coli, is dramatically induced upon cold shock. It was recently reported that there is massive presence of CspA under nonstress conditions, and it is thus claimed that CspA as the cold-shock protein is a misnomer. RESULTS: Here, we re-examined and confirmed that CspA is induced upon culture dilution at 37 degrees C. However, its induction level is one-sixth of the cold-shock-induced level, clearly indicating that the major stress that induces CspA is cold shock. It was further found that CspA induction can be achieved not only by culture dilution but also by the simple addition of nutrients, and that it was almost completely abolished in the presence of rifampicin or nalidixic acid. Nutritional upshift causes the induction of only CspA but not other cold-shock-inducible CspA homologues. The amount of cspA mRNA rapidly and transiently increased by culture dilution, but its stability was not significantly changed. CONCLUSIONS: These results suggest that CspA is a nutritional-upshift stress protein as well as a cold-shock stress protein, and that CspA induction following nutritional upshift may be due to transcriptional activation.

Anti-Infective Agents↗
PubMed2001

Centrifuge polarizing microscope. I. Rationale, design and instrument performance.

We first describe early uses of the centrifuge for deciphering physical properties and molecular organization within living cells, as well as the development and use of centrifuge microscopes for such studies. The rationale for developing a centrifuge microscope that allows high-extinction polarized light microscopy to observe dynamic fine structures in living cells is next discussed. We then describe a centrifuge polarizing microscope (CPM) that we developed for observing fine structural changes in living cells which are being exposed to up to approximately 11 500 times earth's gravitational field (g). With the specimen housed in a rotor supported on an air spindle motor, and imaged through an external microscope illuminated by a precisely synchronized flash of less than 10 ns duration from a Nd:YAG laser, the image of the spinning object remains steady up to the maximum speed of 11 700 rev min-1, or up to approximately 11 500 x g. The image is captured, at up to 25 frames s-1, by an interference-fringe-free CCD camera that is synchronized to the centrifuge rotor. At all speeds (in 100 rev min-1 increments), the image is resolved to better than 1 microm, while birefringence of the specimen, housed in a specially designed specimen chamber that suffers low-stress birefringence and prevents leakage of the physiological solutions, is detected with a retardance sensitivity of better than 1 nm. Differential interference contrast and fluorescence images (532 nm excitation) of the spinning specimen can also be generated with the CPM. The second part of this study (Inoué et al., J. Microsc. 201 (2001) 357-367, describes several biological applications of the CPM that we have explored. Individual live cells, such as oocytes and blood cells, are supported on a sucrose or Percoll density gradient while other cells, such as cultured fibroblasts and Dictyostelium amoebae, are observed crawling on glass surfaces. Observations of these cells exposed to the high G fields (centripetal acceleration/g) in the CPM are yielding many new results that lead to intriguing questions regarding the organization and function of fine structures in living cells and related quasi-fluid systems.

Animals↗
PubMed2001

CspD, a novel DNA replication inhibitor induced during the stationary phase in Escherichia coli.

CspD is a stationary phase-induced, stress response protein in the CspA family of Escherichia coli. Here, we demonstrate that overproduction of CspD is lethal, with the cells displaying a morphology typical of cells with impaired DNA replication. CspD consists mainly of beta-strands, and the purified protein exists exclusively as a dimer and binds to single-stranded (ss)DNA and RNA in a dose-dependent manner without apparent sequence specificity. CsdD effectively inhibits both the initiation and the elongation steps of minichromosome replication in vitro. Electron microscopic studies revealed that CspD tightly packs ssDNA, resulting in structures distinctly different from those of SSB-coated DNA. We propose that CspD dimers, with two independent beta-sheets interacting with ssDNA, function as a novel inhibitor of DNA replication and play a regulatory role in chromosomal replication in nutrient-depleted cells.

Amino Acid Sequence↗
PubMed2001

Psychrophilic valine dehydrogenase of the antarctic psychrophile, Cytophaga sp. KUC-1: purification, molecular characterization and expression.

We found the occurrence of valine dehydrogenase in the cell extract of a psychrophilic bacterium, Cytophaga sp. KUC-1, isolated from Antarctic seawater and purified the enzyme to homogeneity. The molecular mass of the enzyme was determined to be approximately 154 kDa by gel filtration and that of the subunit was 43 kDa by SDS/PAGE: the enzyme was a homotetramer. The enzyme required NAD+ as a coenzyme, and catalyzed the oxidative deamination of L-valine, L-isoleucine, L-leucine and the reductive amination of alpha-ketoisovalerate, alpha-ketovalerate, alpha-ketoisocaproate, and alpha-ketocaproate. The reaction proceeds through an iso-ordered bi-bi mechanism. The enzyme was highly susceptible to heat treatment and the half-life at 45 degrees C was estimated to be 2.4 min. The kcat/Km (micro(-1).s(-1)) values for L-valine and NAD+ at 20 degrees C were 27.48 and 421.6, respectively. The enzyme showed pro-S stereospecificity for hydrogen transfer at the C4 position of the nicotinamide moiety of coenzyme. The gene encoding valine dehydrogenase was cloned into Escherichia coli (Novablue), and the primary structure of the enzyme was deduced on the basis of the nucleotide sequence of the gene encoding the enzyme. The enzyme contains 370 amino-acid residues, and is highly homologous with S. coelicolor ValDH (identity, 46.7%) and S. fradiae ValDH (43.1%). Cytophaga sp. KUC-1 ValDH contains much lower numbers of proline and arginine residues than those of other ValDHs. The changes probably lead to an increase in conformational flexibility of the Cytophaga enzyme molecule to enhance the catalytic activity at low temperatures.

Amino Acid Oxidoreductases↗
PubMed2001

Expression of endothelial nitric oxide synthase in the Sertoli cells of men with infertility of various causes.

OBJECTIVE: To investigate how endothelial nitric oxide (eNOS) expression in the seminiferous tubules might be related to spermatogenesis, by examining eNOS expression in testicular tissue of patients infertile from various causes. PATIENTS AND METHODS: The study included five fertile men with a normal sperm concentration, nine patients with obstructive azoospermia, 20 with varicocele testes and eight with idiopathic azoospermia (Sertoli cell-only syndrome). Testicular biopsy specimens were examined by immunohistochemistry for eNOS protein expression, in addition to a routine pathological assessment. eNOS protein was detected using an eNOS monoclonal antibody. A Sertoli cell staining index (SSI) was defined as the ratio of stained Sertoli cells per total number of Sertoli cells, and was compared among the groups. RESULTS: eNOS was localized to Sertoli cells in the seminiferous tubules and Leydig cells in the interstium; although some degenerating germ cells stained, normal germ cells did not. The SSI was significantly lower in patients with Sertoli cell-only syndrome than in either fertile men or patients with obstructive azoospermia or varicocele. However, the SSI did not correlate significantly with the Johnsen score. CONCLUSION: The expression of eNOS in Sertoli cells may depend on the existence of germ cells and be associated with germ cell development.

Adult↗
PubMed2001

The treatment of skull base meningiomas--combining surgery and radiosurgery.

While the operative results for treating skull base meningiomas have improved due to modern microsurgical techniques, surgery is still accompanied by a high morbidity rate. Over the last 6 years, we operated on 50 patients with intracranial meningiomas, 23 of which were skull-based lesions. Among these patients with skull base meningiomas, seven (30%) were treated with both surgery and radiosurgery. All patients received standard operative procedures. Five patients received subtotal resections and two patients received partial resections. No mortalities occurred in our series. Following the operations, the clinical status improved in six patients, while only one patient (with a tuberculum sellae meningioma) experienced deterioration of a preexisting visual disturbance. Radiosurgery was performed at a mean of 4.3 months after the operations. One patient was treated by a two-staged radiosurgery regimen in light of the patient's large tumour volume (57.5 cm(3)). The treatment volume of the series ranged from 0.3 to 29.6 cm(3)(mean 11.6 cm(3)), and the minimum dose for the tumours was from 8 Gy to 12 Gy (mean, 11.6 Gy). Tumour regression was observed in three patients (43%) during the follow up period for radiosurgery (mean: 28 months). No patients revealed tumour growth in the follow up period or suffered symptomatic radiation injury. The clinical status remained unchanged in each of the seven patients after radiosurgery. Although we treated only seven patients with skull base meningiomas using surgery combined with radiosurgery, and the follow up period has been short, we believe that such combination treatment may be a very useful option in selected patients.

Adult↗
PubMed2001

Left ventricular aneurysm repair in rats: structural, functional, and molecular consequences.

OBJECTIVES: This study examined the effects of aneurysm repair in a rat model of myocardial infarction on functional indices and on the spatiotemporal distribution of cardiac contractile protein and natriuretic peptide messenger RNA. METHODS: In a rat infarct model, expanded left ventricular aneurysms were plicated 4 weeks after infarction. At 30 weeks, transverse heart sections were taken at 4 levels (apex [level 1] through base [level 4]) and assessed by in situ hybridization histochemistry to determine regional messenger RNA levels of pre-pro-atrial natriuretic peptide, cardiac alpha-actin, skeletal alpha-actin, myosin light chain-2v, and beta-myosin heavy chain. RESULTS: Rats with plicated left ventricular aneurysms had reduced left ventricular endocardial circumference (19%, P <.005), lower heart weight ratio (31%, P <.05), left ventricular end-diastolic pressures (51%, P <.05), and increased +/-dP/dt (34%-38%, P <.05). Cardiac messenger RNA levels of pre-pro-atrial natriuretic peptide were reduced in the septum (levels 2 and 3), and skeletal alpha-actin levels were reduced in the septum and left ventricular free wall of plicated rats (level 3). beta-Myosin heavy chain levels were markedly reduced in peri-infarct regions of the left ventricular free wall, septum, and right ventricle in plicated rats at level 4, whereas myosin light chain-2v levels were reduced at levels 2 and 4 in the left ventricular free wall and at level 4 in the right ventricle. CONCLUSIONS: Plication of left ventricular aneurysm after infarction in the rat significantly reduced cardiac hypertrophy, improved cardiac function, and reduced the upregulation of pre-pro-atrial natriuretic peptide and both fetal and adult contractile protein isoforms associated with cardiac hypertrophy.

Actins↗
PubMed2001

Production of secretory leukocyte protease inhibitor by human amniotic membranes and regulation of its concentration in amniotic fluid.

Secretory leukocyte protease inhibitor (SLPI) is a potent inhibitor of human leukocyte elastase. SLPI is a protein found in various human fluids, including parotid secretions, cervical mucus, seminal plasma and ascites. Western blot analysis revealed that SLPI protein is detected as a 12 kDa band in both the amniotic fluid and the amniotic membrane. The amniotic fluid concentrations of SLPI were assayed by enzyme-linked immunosorbent assay. SLPI concentrations in the amniotic fluid of women in the third trimester were higher than those in the second trimester. Immunohistochemistry using an anti-SLPI polyclonal antibody revealed positive staining in epithelial cells in amniotic membranes. Reverse transcription-polymerase chain reaction demonstrated that SLPI transcripts could be detected in the amniotic membranes. To determine the mechanism of SLPI production by amniotic cells, purified amniotic cells were stimulated with various cytokines. Amniotic cells produced SLPI in a dose-dependent manner when stimulated with interleukin (IL)-1alpha, IL-1beta, and tumour necrosis factor-alpha. The present findings show that SLPI is produced by the amniotic membranes in response to cytokine concentrations. The SLPI in the amniotic fluid may contribute to immunodefence mechanisms during pregnancy.

Amniotic Fluid↗
PubMed2001

Secreted type of modified interleukin-18 gene transduced into mouse renal cell carcinoma cells induces systemic tumor immunity.

PURPOSE: Interleukin (IL)-18 is a novel cytokine that has been identified as a strong interferon-gamma inducer. IL-18 has bioactivity similar to that of IL-12 and demonstrates antitumor effects. Since IL-18 does not have a signal sequence, we constructed the gene, consisting of the signal sequences of interferon-beta and mature IL-18 complementary (c) DNA. The modified gene was subsequently transduced into a mouse renal cell carcinoma cell line to induce IL-18 secretion from tumor cells to establish whether this IL-18 secreting tumor cell line may induce systemic tumor immunity. MATERIALS AND METHODS: Modified IL-18 cDNA consisting of the signal sequences of interferon-beta and mature type of IL-18 cDNA was constructed by the overlap extension method. The modified and original IL-18 cDNA was transduced into the RenCa mouse renal cell carcinoma cell line. Expression of IL-18 messenger RNA and concentration of IL-18 in the culture supernatant were determined. Direct antitumor and tumor vaccine effects were investigated in syngeneic Balb/c mice. To determine the mechanism of the antitumor effect immunodeficient mice were challenged with IL-18 secreting RenCa cells. RESULTS: Although the modified and original IL-18 genes transduced RenCa showed almost the same level of IL-18 messenger RNA expression, only RenCa cells transduced with modified IL-18 gene secreted IL-18 into the culture supernatant and were completely rejected when transplanted into syngeneic mice. T lymphocytes were involved in this antitumor effect. Moreover, the modified IL-18 transduced RenCa induced tumor vaccine effect against parental RenCa cells injected at a distant site. CONCLUSIONS: Immune gene therapy using modified IL-18 cDNA appears to be effective and IL-18 secreting cancer cells may be a candidate for tumor vaccine therapy.

Animals↗
PubMed2001

Does craniopharyngioma metastasize? Case report and review of the literature.

OBJECTIVE AND IMPORTANCE: A rare case of recurrent craniopharyngioma at an ectopic location is described. This recurrence suggested cerebrospinal fluid seeding. CLINICAL PRESENTATION: A 65-year-old man presented for follow-up of persisting visual field defect. He had undergone total resection of a suprasellar craniopharyngioma via a subfrontal approach 3 years before presentation. Recent magnetic resonance imaging scans revealed a contrast-enhancing tumor with cystic and solid components at the right temporal lobe. The primary tumor bed was intact. INTERVENTION: A temporal craniotomy was performed for total resection of the tumor. Intraoperative findings revealed that the recurrent tumor was anatomically unrelated to the previous surgical track. Histological studies of the tumor specimen demonstrated a benign craniopharyngioma. Cerebrospinal fluid spreading was suspected to be the sole route for the recurrence. CONCLUSION: The case presented here and a review of reports on remote recurrence of craniopharyngioma suggest that care is required during intraoperative handling of the tumor and that long-term follow-up should be performed even in patients whose primary tumor was resected completely.

Aged↗
PubMed2001

Selective mRNA degradation by polynucleotide phosphorylase in cold shock adaptation in Escherichia coli.

Upon cold shock, Escherichia coli cell growth transiently stops. During this acclimation phase, specific cold shock proteins (CSPs) are highly induced. At the end of the acclimation phase, their synthesis is reduced to new basal levels, while the non-cold shock protein synthesis is resumed, resulting in cell growth reinitiation. Here, we report that polynucleotide phosphorylase (PNPase) is required to repress CSP production at the end of the acclimation phase. A pnp mutant, upon cold shock, maintained a high level of CSPs even after 24 h. PNPase was found to be essential for selective degradation of CSP mRNAs at 15 degrees C. In a poly(A) polymerase mutant and a CsdA RNA helicase mutant, CSP expression upon cold shock was significantly prolonged, indicating that PNPase in concert with poly(A) polymerase and CsdA RNA helicase plays a critical role in cold shock adaptation.

Adaptation, Biological↗
PubMed2001

Oral administration of dimethylarsinic acid, a main metabolite of inorganic arsenic, in mice promotes skin tumorigenesis initiated by dimethylbenz(a)anthracene with or without ultraviolet B as a promoter.

Concerning arsenic-induced tumorigenesis, an animal model must be developed for understanding the mechanism of human carcinogenesis by arsenics. To determine whether orally administered dimethylarsinic acid (DMA) promotes and causes the progression of skin tumorigenesis, an animal protocol by topical application of dimethylbenz(a)anthracene (DMBA) with or without UVB, a tumor promoter, in hairless mice was used. The administration of DMA by the oral route promoted not only the formation of papillomas induced by DMBA alone but also the formation of malignant tumors induced by way of the formation of atypical keratoses by treatment with DMBA and UVB. A phenomenon, the progression of keratoses-->atypical keratoses-->squamous cell carcinomas (SCCs), observed in the present study may resemble the development of tumors in arsenic-exposed humans. We also discussed the involvement of a reactive oxygen species (ROS), e.g., the dimethylarsenic peroxy radical [(CH3)2AsOO.], produced during the metabolic processing of DMA, in skin and in multi-organ tumorigenesis.

8-Hydroxy-2'-Deoxyguanosine↗