Molecular epidemiology of methicillin-resistant Staphylococcus aureus in a community hospital in Hiroshima.
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Cross Infection↗
Biomedical subjects
N Shigeto
Publications and source records attributed to N Shigeto.
Epidemiological analysis of methicillin-resistant Staphylococcus aureus in a community hospital in Hiroshima.
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Bacterial Typing Techniques↗
Mathematical simulation of the Wenckebach phenomenon in Purkinje fibers.
We were able to simulate the Wenckebach phenomenon using a model of a one-dimensional cable, consisting of 20 serially connected Purkinje fiber cells represented by the model of McAllister, Noble, and Tsien. The internal resistance between the 10th and 11th cells was modified to five times the normal. To reconstruct the action potential, the derivative equation was solved using a fourth-order Runge-Kutta algorithm. When the first cell of the cable was stimulated, periodically, at an interval of 610 ms, a 9:8 Wenckebach pattern was elicited in the conduction between the tenth and 11th cells. Lower order 5:4, 4:3, 3:2 Wenckebach patterns were observed at pacing cycle length of 605, 600-595, and 590-575 ms, respectively. At a pacing cycle length of 570ms or less, 2:1 block was elicited. In another simulation, only when INa, was 0 could the Wenckebach phenomenon be elicited in a cable model. in which internal cell resistance and membrane capacitance were uniformly set, but in which the INa of the center two cells of the cable were alternated between 1 and 0. A localized increase in internal resistance, a relatively long time constant of deactivation of the delayed rectifier outward current, and a relatively rapid rate of pacing cycle length was necessary to evoke the Wenckebach phenomenon. The conductance of the delayed rectifier current at the end of an action potential increased progressively, except after a dropped beat when it was allowed to decrease. It was concluded that the change of conductance affected the cable property of the fiber and consequently evoked the Wenckebach phenomenon.
Action Potentials↗
Identification of the ligand binding site for the integrin alpha9 beta1 in the third fibronectin type III repeat of tenascin-C.
The integrin alpha9 subunit forms a single heterodimer, alpha9 beta1 that mediates cell adhesion to a site within the third fibronectin type III repeat of tenascin-C (TNfn3). In contrast to at least 3 other integrins that bind to this region of tenascin-C, alpha9 beta1 does not recognize the common integrin recognition motif, Arg-Gly-Asp (RGD). In this report, we have used substitution mutagenesis to identify a unique ligand recognition sequence in TNfn3. We introduced mutations substituting alanine for each of the acidic residues in or adjacent to each of the exposed loops predicted from the solved crystal structure. Most of these mutations had little or no effect on adhesion of alpha9-transfected SW480 colon carcinoma cells, but mutations of either of two acidic residues in the B-C loop region markedly reduced attachment of these cells. In contrast, cells expressing the integrin alphav beta3, previously reported to bind to the RGD sequence in the adjacent F-G loop, attached to all mutant fragments except one in which the RGD site was mutated to RAA. The peptide, AEIDGIEL, based on the sequence of human tenascin-C in this region blocked the binding of alpha9-transfected cells, but not beta3-transfected cells to wild type TNfn3. This sequence contains a tripeptide, IDG, homologous to the sequences LDV, IDA, and LDA in fibronectin and IDS in VCAM-1 recognized by the closely related integrin alpha4 beta1. These findings support the idea that this tripeptide motif serves as a ligand binding site for the alpha4/alpha9 subfamily of integrins.
Amino Acid Sequence↗
Viscoelastic properties of tissue conditioners--influence of molecular weight of polymer powders and powder/liquid ratio and the clinical implications.
The effect of the molecular weight of polymer powders and the polymer powder/liquid ratio on the viscoelastic properties after gelation of tissue conditioners was studied by means of a stress relaxation test. The results are summarized as follows. The lower-molecular-weight polymer powders produced the larger flow after gelation especially at long times. The use of a lower powder/liquid ratio produced a greater flow after gelation at both short times and long times. The difference in the molecular weight of polymer powders and the powder/liquid ratio was found to have no influence on changes in viscoelastic properties with the passage of time. It would be possible to control the viscoelastic properties of tissue conditioners suitable for each clinical purpose by making variations in composition and structure.
Dibutyl Phthalate↗
Setting properties of alginate impression materials in dynamic viscoelasticity.
The viscoelastic properties of three alginate impression materials were investigated. A landmark of working time was calculated using a raw phase-time curve. A landmark of setting time was calculated from an inflection point of the divided difference of the first order in the share modulus-time curve. As a result, the working time was common at the point of delta = 45 degrees in variable frequencies. The mean value was obtained with less deviation. The setting times obtained were similar for variable frequencies. The mean values showed a distinct difference for each impression material.
Alginates↗
[Tuberculosis found among foreigners and treated at the National Hiroshima Hospital or Hiroshima Anti-Tuberculosis Association].
In this study, we investigated 31 foreign patients who had been diagnosed as having pulmonary tuberculosis at the National Hiroshima Hospital or Hiroshima Anti-Tuberculosis Association between 1982 to 1995. Their age ranged from 17 to 63 years, and all of them had been in Japan for less than five years. Twelve of the patients came from South America, 18 from Asia, and one from Egypt. Seven Peruvians had been infected in a tuberculosis outbreak. The reasons of their immigration were job-seeking (14 out of 31), education (8 out of 31), and marriage to Japanese men (6 out of 31). None of them were illegal immigrants. In four women who had married Japanese men, various symptoms such as cough, sputum, and slight fever came on during pregnancy, however, none of them had been diagnosed as having tuberculosis, and consequently they had received no medication during pregnancy. In 6 out of the 8 patients who were college students, their sputa were negative for tubercle bacilli, and they could be treated by chemotherapy as outpatients. In provincial cities, every effort should be made to detect tuberculosis among members of the foreign community who are living under different environments and conditions.
Adolescent↗
Factors influencing gelation time of tissue conditioners.
To investigate the effects of the composition and structure on the gelation of tissue conditioners, we measured gelation time with an oscillating rheometer. Also, the plasticizer factor was determined using linear multiple regression equations with the dependent variable of gelation time and the independent variables of molecular weight, molar volume, solubility parameter and viscosity of plasticizers. The results obtained were (i) gelation time decreased as the average particle size of poly-ethyl-methacrylate was decreased and its weight average molecular weight increased; (ii) gelation time decreased as ethanol content in the liquid increased. It varied depending on the type of plasticizer; (iii) it was suggested that gelation time was explained by linear multiple regression equations with independent variable of molar volume, solubility parameter and viscosity of plasticizer. In particular, the most influential factor was suggested to be molar volume.
Ethanol↗
[An outbreak of tuberculosis involving foreign workers from South America].
A twenty-four year old male Peruvian of Japanese origin, who came to Japan in September 1990 and had been working in a minor factory in a rural area, was admitted to a hospital in March '91 with severe cough. Smear examination of his sputum smear was positive for acid-fast bacilli and his chest X-ray showed multiple cavities (Index case). Subsequent contact examination identified further four patients with pulmonary tuberculosis among his colleagues in the factory, all of whom lived in the same house with the index case. During following three years, further six patients with mycobacteriosis, two Peruvians and four Japanese, were found among the employee of that factory. M. tuberculosis was cultured from the sputa obtained from seven of these eleven patients. Another patient was diagnosed as non-tuberculous mycobacteriosis. Restriction fragment length polymorphism (RFLP) analysis carried out with five strains of M. tuberculosis isolated from these patients revealed the identical RFLP pattern which is uncommon in Japan. Still more, an isolate from another patient was subjected to RFLP analysis by chance, and was found to show the same RFLP pattern. Later epidemiological study revealed that the last patient, a 53 year-old saleswoman of boxlunch, might have some contact with the index case at her booth. Though RFLP analysis was not done for the isolate from the index case, from the identity of RFLP patterns of other isolates, clinical course and epidemiological study, it is considered that six patients were certainly, and two others were probably infected from the index case.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Viscoelastic properties of tissue conditioners--influence of ethyl alcohol content and type of plasticizer.
The effect of both the ethyl alcohol content of liquids and the type of plasticizer on the viscoelastic properties after gelation of tissue conditioners was studied by means of a stress relaxation test. The results are summarized as follows. The liquids containing the larger percentages of ethyl alcohol produced the larger flow after gelation. Furthermore, the ethyl alcohol content had a significant influence on changes in viscoelastic properties with the passage of time. Flow properties were found to reduce rapidly with time of storage with an increase in the ethyl alcohol content. The use of benzyl benzoate produced the larger flow after gelation than dibutyl phthalate, which in turn produced the larger flow than butyl phthalyl butyl glycolate. The type of plasticizer, however, was found to have no influence on changes in viscoelastic properties with the passage of time.
Dental Materials↗
Initial flow of tissue conditioners--influence of composition and structure on gelation.
The effects of the molecular weight of polymer powders, the ethyl alcohol content of the liquids, the type of plasticizer and the polymer powder/liquid ratio on viscoelastic properties during gelation of tissue conditioners were studied with an oscillating rheometer. The results showed that: (i) The gelation time decreased exponentially with increases in molecular weight of the polymer powder and with powder/liquid ratio. There were linear relationships between the log of gelation time, and both the molecular weight of the polymer powder and the powder/liquid ratio. (ii) In general, gelation time decreased exponentially with increases in ethyl alcohol content. However, the relationship between the log of the gelation time and ethyl alcohol content fitted a second-order polynomial. (iii) The type of plasticizer affected gelation time. The order of gelation times was: benzyl benzoate < dibutyl phthalate < butyl phthalyl butyl glycolate. The initial flow of tissue conditioners could be controlled over a wide range by varying the molecular weight of the polymer powders, the ethyl alcohol content, the powder/liquid ratio and the type of plasticizer.
Acrylic Resins↗
Use of plastic bar molded casting in the modification of variably expanding investment to compensate for casting shrinkage of nickel-chromium alloy.
Trial plastic bar molded castings were compared for accuracy with cast crowns by means of a nickel-chromium alloy, which was used to establish the liquid density of variably expanding investments. The plastic bars were invested to evaluate the change of expansion rate in a wide range of six liquid densities from 0% to 100%, and the distances between the sections were measured before and after casting. Wax crowns were cast to obtain a more detailed relation around 0% expansion at seven liquid densities, and the gaps between the base of the die and the margin of the crown were measured before and after casting. The expansion rates of both castings were calculated and thus were proportional to the liquid density; both regression curves indicated high correlation coefficients. As a result of the statistics of the Student's t-test, the difference between the two methods was not significant. The trial plastic bar was useful in establishing the variably expanding investment for precise casting of artificial crowns.
Chromium Alloys↗
Shrinkage of tissue conditioners with time--effect of the particle size in powder and the EtOH content in liquid.
The dimensional change of tissue conditioners with time was measured until 4 weeks after mixing. Shrinkage of the materials was evaluated in relation to particle size in powder and the EtOH content in liquid. The dissolution of EtOH and plasticizer were also measured to investigate the relation to dimensional change. Shrinkage with time was recorded. The smaller the particle size in powder and the more EtOH in liquid, the greater the shrinkage rate. The smaller the particle size in the powder and the more EtOH contained in the liquid, the greater the dissolution of EtOH. The dissolution of BPBG was below 1/100 comparing that of EtOH and no difference was recognized by particle size and EtOH content. On the basis of these results it is suggested that the dissolution of EtOH is related to shrinkage of tissue conditioners with time and that the component particle size in the powder and EtOH content in the liquid have a significant influence on dissolution of EtOH associated with shrinkage.
Chromatography, Gas↗
Corrosion properties of soldered joints. Part II: Corrosion pattern of dental solder and dental nickel-chromium alloy.
Six nickel-chromium (Ni-Cr) alloys joined with two solders were evaluated for degree of corrosion after they were immersed in corrosive solution for 100 days. The corroded surface of the Ni-Cr alloy and the cross section of the soldered joint were observed and the solution of nickel and copper (Cu) ions in each combination was measured. No corrosion was observed in the high-resistant Ni-Cr alloys with high Cr content. Pitting corrosion was seen on low-resistant Ni-Cr alloys, which had less Cr content. In the cross section of the joint, the joint of silver solder became porous by corrosion and the corrosion advanced especially along the interface. Solution of Ni ions was detected in all of the combinations of Ni-Cr alloys and solders with exception of the combination of high-resistant Ni-Cr alloys and gold solder. On the other hand, solution of Cu ions was detected in all of the combinations with silver solder.
Chromium↗
Na/K pump current in aggregates of cultured chick cardiac myocytes.
Spontaneously beating aggregates of cultured embryonic chick cardiac myocytes, maintained at 37 degrees C, were voltage clamped using a single microelectrode switching clamp to measure the current generated by the Na/K pump (Ip). In resting, steady-state preparations an ouabain-sensitive current of 0.46 +/- 0.03 microA/cm2 (n = 22) was identified. This current was not affected by 1 mM Ba, which was used to reduce inward rectifier current (IK1) and linearize the current-voltage relationship. When K-free solution was used to block Ip, subsequent addition of Ko reactivated the Na/K pump, generating an outward reactivation current that was also ouabain sensitive. The reactivation current magnitude was a saturating function of Ko with a Hill coefficient of 1.7 and K0.5 of 1.9 mM in the presence of 144 mM Nao. The reactivation current was increased in magnitude when Nai was increased by lengthening the period of time that the preparation was exposed to K-free solution prior to reactivation. When Nai was raised by 3 microM monensin, steady-state Ip was increased more than threefold above the resting value to 1.74 +/- 0.09 microA/cm2 (n = 11). From these measurements and other published data we calculate that in a resting myocyte: (a) the steady-state Ip should hyperpolarize the membrane by 6.5 mV, (b) the turnover rate of the Na/K pump is 29 s-1, and (c) the Na influx is 14.3 pmol/cm2.s. We conclude that in cultured embryonic chick cardiac myocytes, the Na/K pump generates a measurable current which, under certain conditions, can be isolated from other membrane currents and has properties similar to those reported for adult cardiac cells.
Animals↗
Intracellular sodium affects ouabain interaction with the Na/K pump in cultured chick cardiac myocytes.
Whether a given dose of ouabain will produce inotropic or toxic effects depends on factors that affect the apparent affinity (K0.5) of the Na/K pump for ouabain. To accurately resolve these factors, especially the effect of intracellular Na concentration (Nai), we have applied three complementary techniques for measuring the K0.5 for ouabain in cultured embryonic chick cardiac myocytes. Under control conditions with 5.4 mM Ko, the value of the K0.5 for ouabain was 20.6 +/- 1.2, 12.3 +/- 1.7, and 6.6 +/- 0.4 microM, measured by voltage-clamp, Na-selective microelectrode, and equilibrium [3H]ouabain-binding techniques, respectively. A significant difference in the three techniques was the time of exposure to ouabain (30 s-30 min). Since increased duration of exposure to ouabain would increase Nai, monensin was used to raise Nai to investigate what effect Nai might have on the apparent affinity of block by ouabain. Monensin enhanced the rise in Na content induced by 1 microM ouabain. In the presence of 1 microM [3H]ouabain, total binding was found to be a saturating function of Na content. Using the voltage-clamp method, we found that the value of the K0.5 for ouabain was lowered by nearly an order of magnitude in the presence of 3 microM monensin to 2.4 +/- 0.2 microM and the magnitude of the Na/K pump current was increased about threefold. Modeling the Na/K pump as a cyclic sequence of states with a single state having high affinity for ouabain shows that changes in Nai alone are sufficient to cause a 10-fold change in K0.5. These results suggest that Nai reduces the value of the apparent affinity of the Na/K pump for ouabain in 5.4 mM Ko by increasing its turnover rate, thus increasing the availability of the conformation of the Na/K pump that binds ouabain with high affinity.
Animals↗
Viscoelastic properties of tissue conditioners--stress relaxation test using Maxwell model analogy.
In order to measure the viscoelastic properties of tissue conditioners, a series of stress relaxation tests was carried out using poly ethyl methacrylate polymer powders and liquids composed of butyl phthalyl butyl glycolate/ethyl alcohol mixtures, respectively. The analysis method using the Maxwell model analogy is discussed. The results may be summarized as follows. (i) In this study it was feasible to make the stress relaxation curves for 30 min analogous to the Maxwell model, using a model with a maximum of 5 elements. (ii) The elastic modulus Ei, the coefficient of viscosity eta i, and relaxation time tau i, for each element, and the instantaneous modulus E0, tended to increase with time. These values in the element of the longest relaxation time were most marked in the increase among those in all the elements. Furthermore, in every element the rate of increase of eta i was greater than that of Ei. The method described is considered to be one of the most useful techniques available for the study of the viscoelastic properties of tissue conditioners.
Chemical Phenomena↗
A method of determining residual monomer in acrylic resin using methyl ethyl ketone.
An improved method of extraction of residual monomer from acrylic resin has been described for determination of the concentration of residual monomer by gas chromatography. Four kinds of organic solvent selected according to their physicochemical properties (methanol, N,N-dimethylformamide, ethyl acetate and methyl ethyl ketone) were tested for their capacity to extract residual monomer at varying temperatures and time periods. Extraction with methyl ethyl ketone at 4 degrees C was found to be the most effective. The method is simpler and more effective than others reported so far, and therefore seems to be suitable for clinical laboratory use.
Acetates↗