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Biomedical subjects

H Koizumi

Publications and source records attributed to H Koizumi.

At least 19 recordsLinked to original sources
PubMed2006

Sodium hyaluronate eye drops prevent late-onset bleb leakage after trabeculectomy with mitomycin C.

PURPOSE: To evaluate the efficacy of sodium hyaluronate eye drops for prevention of late-onset bleb leakage after trabeculectomy with mitomycin C (MMC). METHODS: Sixty-eight patients (68 eyes) who had trabeculectomy with MMC from March 1995 to February 2002 at the Marui Eye Clinic or the Department of Ophthalmology, Fukushima Medical University Hospital were examined in this study. Twenty-two were treated postoperatively with sodium hyaluronate eye drops (sodium hyaluronate group) and 46 eyes were not treated postoperatively (control group). The blebs were classified according to the avascular area, epithelial defect and degree of bleb wall leakage. Both groups were assigned classes (0, avascular or partial avascular bleb; 1, avascular or partial avascular bleb with an epithelial defect; 2, avascular or partial avascular bleb with oozing; 3, avascular or partial avascular bleb with a point of leakage). RESULTS: Follow-up duration ranged from 10 to 116 months (mean+/-SD, 57.6+/-30.5). The incidence of reclassification from class 1 to class 0 was significantly greater in the sodium hyaluronate group (four of six class 1 eyes improved to class 0 after application of sodium hyaluronate eye drops) than in the control group (zero of 10 eyes) (P=0.008). And, the incidence of reclassification from class 1 to class 2 or class 3 was significantly smaller in the sodium hyaluronate group (one of six eyes) than in the control group (nine of 10 eyes) (P=0.008). CONCLUSIONS: Sodium hyaluronate eye drops may prevent late-onset bleb leakage after trabeculectomy with MMC.

Adult↗
PubMed2006

Intrinsic bursters increase the robustness of rhythm generation in an excitatory network.

The pre-Botzinger complex (pBC) is a vital subcircuit of the respiratory central pattern generator. Although the existence of neurons with pacemaker-like bursting properties in this network is not questioned, their role in network rhythmogenesis is unresolved. Modeling is ideally suited to address this debate because of the ease with which biophysical parameters of individual cells and network architecture can be manipulated. We modeled the parameter variability of experimental data from pBC bursting pacemaker and nonpacemaker neurons using a modified version of our previously developed pBC neuron and network models. To investigate the role of pacemakers in networkwide rhythmogenesis, we simulated networks of these neurons and varied the fraction of the population made up of pacemakers. For each number of pacemaker neurons, we varied the amount of tonic drive to the network and measured the frequency of synchronous networkwide bursting produced. Both excitatory networks with all-to-all coupling and sparsely connected networks were explored for several levels of synaptic coupling strength. Networks containing only nonpacemakers were able to produce networkwide bursting, but with a low probability of bursting and low input and output ranges. Our results indicate that inclusion of pacemakers in an excitatory network increases robustness of the network by more than tripling the input and output ranges compared with networks containing no pacemakers. The largest increase in dynamic range occurs when the number of pacemakers in the network is greater than 20% of the population. Experimental tests of our model predictions are proposed.

Afferent Pathways↗
PubMed2006

Primary germinoma arising from the midbrain.

A 29-year-old man presented with diplopia, dysarthria, anisocoria, oculomotor nerve paralysis, abducens nerve paralysis, right facial palsy, and spastic hemiparetic gait. Magnetic resonance imaging (MRI) showed a homogenously enhanced mass in the midbrain. MRI-guided stereotactic biopsy was performed, and the histologic diagnosis was pure germinoma. The tumor disappeared after chemotherapy and radiotherapy. Germinoma should be included in the differential diagnosis of midbrain lesions in young adults. MRI-guided stereotactic biopsy provided a helpful diagnostic clue in a patient with a midbrain lesion.

Adult↗
PubMed2006

Observation of all the components of elastic constants using tetragonal hen egg-white lysozyme crystals dehydrated at 42% relative humidity.

Success in measuring transverse sound velocity allowed us to determine, for the first time, all six elastic constants of a protein crystal. An ultrasonic pulse-echo method was used to perform sound velocity measurements on tetragonal hen egg-white (HEW) lysozyme crystals that were partially dehydrated at 42% relative humidity. The measurements were performed using the (110), (101), and (001) crystallographic faces. Thus, all six elastic constants of the dehydrated tetragonal HEW lysozyme crystals were determined: C11=C22=12.44 GPa, C12=7.03 GPa, C13=C23=8.36 GPa, C33=12.79 GPa, C44=C55=2.97 GPa, and C66=2.63 GPa. In addition, for the hydrated crystals, the longitudinal sound velocities along the [110] direction and the direction normal to the (101) face were measured. From these results, all the components of elastic constants in the hydrated crystals were extrapolated.

Animals↗
PubMed2004

Effect of intracrystalline water on longitudinal sound velocity in tetragonal hen-egg-white lysozyme crystals.

Longitudinal sound velocity of tetragonal hen-egg-white (HEW) lysozyme crystals was measured during air drying by ultrasonic pulseecho method. The sound velocity increases with exposure to open air and approaches a constant value. The maximum value is approximately 2900 m/s that is about 1.6 times as much as that of original one before drying. In addition, the sound velocity clearly recovers to original one after immersing the dried crystal in solution. Therefore, the sound velocity in tetragonal HEW lysozyme crystals can be reversibly changed due to dehydration and rehydration. These changes in sound velocity are discussed in the light of water-mediated intramolecular and intermolecular interactions in the crystals.

Animals↗
PubMed2004

Comparative strength of metal-ceramic and metal-composite bonds after extended thermocycling.

The relative strengths of ceramic-to-metal and composite-to-metal bonds were compared after prolonged thermocycling. A total of 104 cast discs were produced from a gold alloy (Pontor LFC). A ceramic material (Duceragold) was fused to 24 discs to assess the strength of the metal-ceramic bond. An indirect composite material (New Metacolor Infis) was bonded to the remaining discs after surface preparation by Rocatec tribochemical coating, tin plating and priming with a phosphate conditioner [10-methacryloyloxydecyl dihydrogen phosphate (MDP), Cesead II], priming with a thione conditioner (V-Primer) or no treatment (unprimed control). Shear bond strengths were determined before and after thermocycling at 20,000 and 100,000 cycles. Pre-thermocycling bond strengths were ranked in the order: metal-ceramic (40.5 MPa); Rocatec treatment (33.1 MPa) and tin plating-MDP (31.0 MPa); V-Primer (20.9 MPa); and control (11.9 MPa). The bond strengths of the first three groups were not significantly different after 20,000 thermocycles, whereas those of the V-Primer and control groups were significantly reduced. After extended thermocycling (100,000 cycles) the metal-ceramic group had the highest mean shear bond strength (28.5 MPa; P < 0.05), followed by the Rocatec (23.9 MPa) and tin plating-MDP (22.1 MPa) groups. The metal-ceramic bond was the most durable, although its strength was reduced by 29.6% after extended thermocycling. On the basis of these results, we recommend the Rocatec and tin plating-MDP systems for composite-to-metal bonding. Metal-ceramic bonding, however, is superior to metal-composite bonding within the limitation of the current experiment.

Analysis of Variance↗
PubMed2003

Identification of dislocations in large tetragonal hen egg-white lysozyme crystals by synchrotron white-beam topography.

Large tetragonal hen egg-white (HEW) lysozyme crystals have been grown by a salt concentration-gradient method. The grown crystals, of thicknesses greater than 1.5 mm, were observed by means of X-ray topography using white-beam synchrotron radiation. Line contrasts clearly appeared on the Laue topographs. Extinction of the line images was observed in specific reflections. These results mean that the observed lines correspond to dislocation images. From the extinction criterion it is shown that the predominant dislocations are of screw character with <110> Burgers vectors. In addition, dislocation loops with [001] Burgers vectors have been found in a tetragonal HEW lysozyme crystal including some cracks. These results are discussed in the light of dislocation elastic energy and slip systems in the crystals.

Animals↗
PubMed2002

Effect of serotonin (5-HT) on trigeminal rhythmic activities generated in in vitro brainstem block preparations.

We used rat isolated brainstem block preparations to analyze the functional roles of serotonin receptors in the generation of trigeminal rhythmic activities. We previously reported that trigeminal rhythmic activities could be induced by some pharmacological applications in an isolated brainstem preparation with a rostral boundary at the border between the inferior and superior colliculus, and a caudal border at the level of the rostral facial nucleus. However, the same stimulation did not induce trigeminal rhythmic activities in a whole brainstem block preparation with the same rostral boundary and a caudal border at the obex level. In the present study, both the 5-HT(1A) phthalimido-butyl-piperazine, and the 5-HT(2C) agonist, 1-2,5-dimethoxy-4-iodophenyl-2-aminopropane, combined with N-methyl-D,L-aspartate and bicuculline, elicited trigeminal rhythmic activities in a whole brainstem block preparation. Our results suggest that serotonin has both facilitation and inhibition effects on the generation of trigeminal rhythmic activities in an isolated brainstem block preparation in vitro.

Animals↗
PubMed2001

High serum levels of additional IL-18 forms may be reciprocally correlated with IgE levels in patients with atopic dermatitis.

We established an ELISA system for determination of as yet unidentified species of interleukin 18 (IL-18), named IL-18 type 2, in human serum. Serum IL-18 levels and their effect on IgE levels were examined in 18 patients with atopic dermatitis (AD) with no other allergic symptoms. Three of these patients showed high IL-18 type 2 concentrations (25-100 ng/ml) in their blood serum, and this IL-18 type 2 was detectable only with our established ELISA system. In contrast, the level of the conventional form of IL-18 (type 1) was found to be 50-400 pg/ml in all patients by the commercially available ELISA. The levels of type 1 IL-18 showed no correlation with those of type 2 and approximately 2-fold higher in AD patients than in normal subjects. IL-12 p40 and IgE levels were correlated in the patients with no IL-18 type 2, and interestingly, relatively low IgE concentrations were detected in the three IL-18 type 2-positive patients. They showed considerable levels of IL-12 p40 unlike normal subjects. The IFNgamma-inducing activity of IL-18 type 2 was >100-fold less potent by weight ratio than that of a recombinant 'active' IL-18 preparation, even after the treatment with Caspase 1. Although the relationship between AD and serum IgE levels is not clear cut, IL-18 type 2 appears to play some roles in the Th2-polarization involving IgE production in association with immune responses occurring in local inflammatory milieu such as atopic lesions.

Adolescent↗
PubMed2001

Study of the e(g) orbitals in the bilayer manganite La(2--2x)Sr(1+2x)Mn(2)O(7) by using magnetic Compton-profile measurement.

From the magnetic Compton-profile (MCP) measurement, we have directly differentiated for the first time the populations in two e(g)-type orbitals ( x(2) - y(2) and 3z(2) - r(2)) in a manganite. The experimental MCP's along the [001] direction for La(2--2x)Sr(1+2x)Mn(2)O(7) at x = 0.35 and 0.42 are fitted by the theoretical profiles obtained from the (MnO(6))(8-) ab initio calculations. The calculation confirms that the MCP clearly detects the oxygen hybridization in the e(g) orbitals. The e(g) state is dominated by the x(2) - y(2)-type orbital with almost constant population, while the population in the 3z(2) - r(2)-type orbital decreases with increasing the hole concentration x.

Journal Article↗
PubMed2001

In vitro ubiquitination of cyclin D1 by ROC1-CUL1 and ROC1-CUL3.

Overexpression of cyclin D1 has been implicated in a variety of tumors, such as breast cancers, gastrointestinal cancers and lymphomas. Both gene amplification and protein degradation mediated by ubiquitin (Ub)-dependent proteolysis regulate the abundance of cyclin D1. Here we report that ROC1 interacted with all three D type cyclins in vivo but did not bind to other cyclins tested. The ROC1-CUL1 and ROC1-CUL3, but not ROC1-CUL2, -CUL3 and -CUL4, immunocomplexes promoted polyubiquitination of bacterially purified cyclin D1 in vitro. RING finger mutations of ROC1 eliminated the Ub ligase activity toward cyclin D1. In all cases the ubiquitination of cyclin D1 was accompanied by autoubiquitination of the cullins. The results suggest the involvement of ROC1-cullin ligases in cyclin D1 ubiquitination and a potential mechanism whereby the cullin subunit is ubiquitinated itself while ubiquitinating a substrate.

Anaphase-Promoting Complex-Cyclosome↗
PubMed2001

Prognosis of patients with advanced carcinoma of the esophagus with complete response to chemotherapy and/or radiation therapy: a questionnaire survey in Japan.

BACKGROUND: We estimated the survival of patients with advanced carcinoma of the esophagus in Japan who achieved complete response (CR) with chemotherapy and/or radiation therapy. METHODS: A questionnaire was designed for patients with cancer of the esophagus with pretreatment stage II-IV (excluding organ metastasis [M1]), who were treated with chemotherapy and/or radiation therapy and achieved either a clinical CR continuing for more than 1 year, or a pathological CR in surgical specimens. All patients were treated between January 1, 1990, and December 31, 1997, in Japan. RESULTS: Of the 169 eligible patients for whom adequate data were available, 106 patients with continuing clinical CR were defined as group A and 63 with pathological CR as group B. The overall survival rates at 5 years were 62.4% in group A and 64.8% in group B. In each of groups A and B, there was no significant difference in overall survival among subgroups of patients classified by initial pretreatment clinical stage. In group A, the survival rate of patients with concurrent chemotherapy and radiation therapy was significantly better than the rates for patients with chemotherapy alone or radiotherapy alone. In group A, the frequency of first failure at the local site of esophageal carcinoma was 7.7%. Of the 12 patients in group B (19%) who died less than 1 year postoperatively, 6 died of postoperative complications. CONCLUSION: The effect of CR to chemotherapy and/or radiation therapy for carcinoma of the esophagus on survival was marked. In patients with esophageal carcinoma who achieve CR, the prognosis may be independent of the initial pretreatment stage. Local failure in group A patients remains a problem, however.

Adult↗
PubMed2001

Distribution of IL-18 and IL-18 receptor in human skin: various forms of IL-18 are produced in keratinocytes.

Human interleukin-18 (IL-18) enhances IL-12-mediated IFN-gamma production by lymphocytes and Fas/perforin-mediated cytolysis by NK cells. IL-18 is synthesized as a 24 kDa proform, and the proform is processed in the cytoplasm into an 18 kDa mature form. Active and precursor forms of IL-18 have been detected in immunocompetent cells, and active IL-18 exerts its functions through its receptor. We sought to determine which human skin cells are responsible for production of IL-18 and which express its receptor. Monoclonal antibodies against human IL-18 and polyclonal antibody against IL-18 receptor were provided for this analysis. Formalin-embedded and frozen sections of human epidermis were analyzed by immunoperoxidase and immunofluorescence staining. IL-18 was detected in all living cell layers of the epidermis, hair follicles, arrectores pilorum, eccrine ducts and endothelial cells. IL-18 was localized in the cytoplasm of cells in living epidermal cell layers. In contrast, IL-18 receptor was mainly detected in keratinocytes and expressed in the cell periphery in living cell layers. Since keratinocytes were the main source of IL-18 and its receptor, cultured human keratinocytes were further analyzed by immunoblotting. IL-18 receptor was identified as an 80 kDa single band. The mature 18 kDa and precursor 24 kDa forms of IL-18 were detected by our monoclonal antibody (mAb) 21 and mAb 132, respectively, while only the 18 kDa form was detected by a commercial mAb, 125-2H. Cultured keratinocytes showed positive granular staining for IL-18 in the cytoplasm and positive staining for IL-18 receptor mainly in the cell periphery. Our findings indicate that mature IL-18, precursor IL-18 and IL-18 receptor are simultaneously expressed with different localizations by human epidermal keratinocytes. Keratinocytes might be activated by their own IL-18 in an autocrine or paracrine fashion.

Adult↗
PubMed2001

Quantitative high-resolution microscopy on a suspended chain of gold atoms.

High-resolution electron microscope images of a suspended gold chain were analyzed quantitatively. The images of the suspended gold chain were recorded on videotapes, during in situ observation in an ultra-high-vacuum electron microscope. The chain consisted of four gold atoms free from any substrate. Image simulation verified that the gold chain has a center-top geometry. The simulation also showed that the chain has no glue atoms spinning around the axis of the chain. A spinning gold atom was shown to give 50% of the stationary atom in gray scale. By comparing the noise level of the observed image and the gray scale of single atoms such as C, Si, S, Cu, and Au, we verified that the Si and S atoms have almost twice as large contrast as the noise (peak-to-peak), and C atoms have almost the same contrast as the noise level. The analysis showed it critical to detect a single Si and S atoms.

Journal Article↗
PubMed2001

Collision-induced dissociation and theoretical studies of Cu+-dimethoxyethane complexes.

Collision-induced dissociation of the dimethoxyethane (DXE) complexes with copper ions, Cu+(DXE)n, n = 1 and 2, is studied using kinetic energy dependent guided ion beam mass spectrometry. For Cu+(DXE)2, the only product formed corresponds to endothermic loss of a neutral ligand, while the Cu+ (DXE) complex dissociates by several competitive channels. The cross-section thresholds for single ligand loss are interpreted to yield 0 and 298 K bond energies for Cu+-DXE and (DXE)Cu+-DXE after accounting for the effects of multiple ion-molecule collisions, internal energy of the reactant ions, and dissociation lifetimes. We find absolute 0 K bond dissociation energies for these complexes of 2.74+/-0.08 and 1.87+/-0.06 eV, respectively. These values are compared with theoretical values obtained using density functional and second order Møller-Plesset perturbation, MP2, theories. We also compare our results with previously studied alkali cation-ether complexes. Although Cu+ and all alkali cations have 1S electronic ground states, the comparison shows different trends for Cu+ because of hybridization effects involving the valence d-electrons.

Journal Article↗