Biomedical subjects

H Shintani

Publications and source records attributed to H Shintani.

157 records · Page 9Linked to original sources

PubMedDate not supplied

Analysis of a carcinogen, 4,4'-methylenedianiline, from thermosetting polyurethane during sterilization.

Polyurethane (PU) is widely used in medical devices such as potting material in artificial dialysis devices, plasma separators, etc. Gamma-ray irradiation is frequently used for the sterilization of such devices. This paper reports that a carcinogen, 4,4'-methylenedianiline (MDA, p,p'-diaminodiphenylmethane), is produced from medical thermosetting PU by gamma-ray irradiation. Gamma-ray irradiated PU was immersed in methanol or equine serum. The serum was treated with a mixture of 5N HCIO4:acetonitrile (1:10) in order to deproteinate and recover MDA. It was found that MDA is formed from thermosetting PU at around a few ppm in the original sample. The production of MDA increased with increasing irradiation dose. The MDA amount formed was related to the irradiation dose by a second order equation. Results of methanol and serum extraction were similar. Pressurized steam (autoclave) sterilization in place of gamma-ray sterilization was also examined. MDA production was not found in autoclave sterilization procedures. Gel permeation chromatography (GPC) of methanol or N,N-dimethylformamide (DMF) extract of irradiated PU showed that the PU oligomers eluted. Time course of methanol extract of irradiated PU was detected at 245.5 nm. This showed an exponential decline regardless of doses of irradiation.

Aniline Compounds↗

PubMedDate not supplied

Solid-phase extraction of a carcinogen, 4,4'-methylenedianiline, in serum.

Polyurethane (PU) is a material used to make medical devices. During the gamma-ray or autoclave sterilization of these medical devices, PU degrades and a carcinogen, 4,4'-methylenedianiline (MDA), is produced. We studied a pretreatment method for MDA in blood serum by solid-phase extraction. Using Bond Elut C18, phenyl, and cyclohexyl columns, MDA in serum at a concentration of 0.1-10 ppm was 100% recovered with no apparent difference between the columns tested. Elution was carried out with methanol containing 1M MH4OH. The recovery rate of serum MDA with a Bond Elut C8 column was 90%, less than that from the above columns. The recovery of serum MDA from Bond Elut C1, C2, and silica was unsatisfactory. The recovery rate with Bond Elut SCX (strong cation exchange column) proved satisfactory, but the pretreatment of serum was troublesome as both deproteinization and centrifugal separation procedures were necessary in addition to the complicated conditioning procedure of the SCX column. There was no significant difference in recovery rate among C18, phenyl, and cyclohexyl columns, indicating that both pi-pi binding between benzene rings and van der Waals binding would be predominant. Because Bond Elut silica showed a lower recovery rate, the binding of NH2 in MDA with free silanol would not be predominant.

Aniline Compounds↗

PubMedDate not supplied

Solid phase extraction and HPLC analysis of toxic components eluted from methyl methacrylate dental materials.

Methyl methacrylate polymer (PolyMMA) is widely used as the composite resin for the dental plate. During the fabrication process of PolyMMA for the polymerization reaction, benzoylperoxide (BPO) and N,N-dimethyl p-toluidine (DMPT) are added as the initiator and the stimulator, respectively. Because these compounds exhibit toxicity as well as a residue potential, their use raises concerns regarding human safety. The degree of dissolution into serum was determined to evaluate risk to the user. Analysis was by HPLC combined with solid-phase extraction using a C-18 column. The eluted compounds were found to be in the order of 10 to 100 ppm.

Benzoates↗

PubMedDate not supplied

Improved management of selective cerebral perfusion in aortic arch surgery.

To establish a safe and reliable method for cerebral protection in aortic arch surgery, the authors attempted antegrade selective cerebral perfusion (SCP) based on the characteristics of jugular venous oxygen saturation (SjO2). Twenty patients were divided into two groups: a control group and SCP group. In the control group, in 13 adult patients undergoing cardiac surgery using standard hypothermic cardiopulmonary bypass, the relationship between SjO2 and nasopharyngeal temperature (NPT) during rewarming showed an inverse linear correlation:SjO2 = -2.3 NPT + 133 (r = 0.616). In the SCP group, seven patients with aortic arch aneurysm underwent surgery using SCP performed through direct cannulation of the innominate and left carotid arteries. While on SCP (83 +/- 24 min), the blood was warmed from 28 to 36 degrees C. Cerebral perfusion pressure of 40-60 mm Hg was necessary to maintain the SjO2 equal to the value in the control group at each NPT during SCP in all seven patients. None of the patients had any post operative complications. Our experience suggests that SCP can be safely performed at both mild hypothermia and normothermia under monitoring of perfusion pressure and SjO2 in aortic arch surgery.

Adult↗

PubMedDate not supplied

Influence of sodium and potassium ions on the contraction induced by calcium ions in guinea-pig isolated vas deferens.

1. When guinea-pig isolated vas deferens was pretreated with 0.01% tetrasodium edetate in an isotonic sucrose medium and then transferred to an edetate-free sucrose medium, the addition of CaCl2 (0.28-8.80 mmol/l) induced a contraction. 2. When the edetate-free sucrose medium was replaced by saline containing NaHCO3 and glucose, the contraction induced by CaCl2 was only slightly smaller than that obtained in the sucrose medium. 3. When the saline medium was replaced by Ca-free Locke's solution, the contraction induced by CaCl2 was almost the same as that obtained in the saline medium. 4. When the Ca-free Locke's solution was replaced by Ca-free K-Locke's solution (in which NaCl and CaCl2 were replaced by KCl), the contraction induced by CaCl2 was almost the same as that obtained in the sucrose medium.

Animals↗

PubMedDate not supplied

Influence of manganese ions on the contraction of the guinea-pig isolated vas deferens.

1. The CaCl2-induced contraction of guinea-pig isolated vas deferens, pretreated with tetrasodium edetate and then transferred to edetate-free sucrose medium, was increased in the presence of MnCl2 in extremely low concentrations (0.005-0.01 mmol/l) but was suppressed by the salt in concentrations higher than 1.0 mmol/l. 2. The KCl-induced contraction of the preparation, kept in a sucrose medium without edetate-pretreatment, was suppressed by MnCl2 (0.005-0.5 mmol/l) in a concentration-dependent manner. 3. The noradrenaline-induced contraction of the preparation kept in Locke's solution, was not influenced by MnCl2 in concentrations lower tha 0.1 mmol/l but was inhibited by higher concentrations (0.1-1.0 mmol/l).

Animals↗

PubMedDate not supplied

Validation of D value by different SCD culture medium manufacturer and/or different SCD culture medium constituent.

Variation in decimal reduction (D) time/value for attaining sterility assurance was reported in terms of difference between lot to lot and/or manufacturer to manufacturer of soybean casein digest (SCD) culture medium. The D value variation phenomenon itself due to SCD culture medium was reported by Graham et al; however, it was not sufficiently clarified what constituent(s) of SCD culture medium would mainly contribute to the variation of D value. If it is not well clarified, the reproducible sterility assurance cannot be successfully attained. The authors studied individually the constituent of SCD broth (SCDB), SCD agar (SCDA) and SCD broth plus 1.5% agar (SCDB/A). As a result, the culture medium constituent causing D value variation among SCD culture medium was determined as the difference of calcium (Ca) amount as well as the presence and the absence of K2HPO4 in SCD culture medium. Additionally, it was clarified D value differed significantly between SCDB and SCDA. D value using the former was around 1 min lower than that using the latter. This phenomenon can be explained from the formation of insoluble CaHPO4 in SCDB culture medium, resulting in insufficiency of usable Ca to B. stearothermophilus in SCDB culture medium.

Caseins↗

PubMedDate not supplied

On the cause of performance variation of biological indicator used for sterility assurance.

Variations in biological indicator (BI) lethality have been reported for several types of commercial BIs. This phenomenon has been observed among different lots of the same species and strain BIs from a single vendor. It has also been reported among BIs from different vendors but of the same species and strain that are intended to challenge the same general type of sterilization process. Although BI variability has been widely reported, the contributing factors to the variation in observed lethality have not been specifically identified. This is because the previous reports overlooked, to some extent, the differences in carrier materials, primary packaging materials, and culture media used in the manufacture of commercial BIs. The differences in lethality attributable to the carrier material, for so called "substrate effects," have been widely reported. For the BI preparation in this experiment, the same carrier material, primary packaging material, and culture medium were used. The only variable was the use of different spore suspensions supplied from different BI manufacturers. The authors found no significant difference in BI performance as measured by BI resistance. BI population may vary depending on the retrieval technique or population variability in a purchased BI suspension. Unlike some previously published studies, there was no indication from our studies that a specific BI manufacturer supplied BIs with either greater resistance or greater population.

Drug Packaging↗

PubMedDate not supplied

Efficacy of transesophageal echocardiography as a perioperative monitor in patients undergoing cardiovascular surgery. Analysis of 149 consecutive studies.

To evaluate the usefulness of transesophageal echocardiography as a perioperative monitor in patients undergoing cardiovascular surgery, 149 consecutive patients were studied since 1985. Left ventricular function was assessed by measurement of left ventricular dimension and ejection fraction in patients with valvular disease. This monitoring was useful in detecting the changes in left ventricular performance in patients with volume overload and in managing patients in the early postoperative period. Cardiac tamponade was clearly demonstrated before changes in electrocardiogram and hemodynamic data. In 27 patients, transesophageal color Doppler echocardiography was used to confirm that there was no residual regurgitation immediately after valvular reconstructive surgery. Transesophageal color Doppler echocardiography was also useful in detecting the entry of false lumen before surgery in 7 patients with dissecting aortic aneurysm. There were no unsuccessful introductions, no traumatic or thermal injuries, 18 patients (12.1%) with hoarseness and 5 patients (3.4%) with transient arrhythmia. In conclusion, transesophageal echocardiography provides a good imaging window to the heart and great vessels perioperatively. This expedient, safe informative imaging method can be used more routinely in patients during surgery.

Adolescent↗

PubMedDate not supplied

Comparison of D10-value accuracy by the limited Spearman-Karber procedure (LSKP), the Stumbo-Murphy-Cochran procedure (SMCP), and the survival-curve method (EN).

The decimal reduction time (D10) may be determined by any of several methods, including the limited Spearman-Karber procedure (LSKP), the Stumbo-Murphy-Cochran procedure (SMCP), and the survival-curve method (EN). The International Organization for Standardization (ISO) endorses the LSKP and the EN. Most Japanese and German industries utilize the SMCP and the EN for calculation of the D value. A presentation at an ISO meeting suggested that the SMCP was less accurate than the LSKP, and the ISO recommended abandoning the SMCP. The paper concerning the accuracy comparison among these methods has not been published. Therefore, in order to examine whether the SMCP was truly inferior to the LSKP, the Japanese delegates to the ISO compared the accuracies of D10 values obtained with these methods by simulation and in experimental procedures using a biological indicator (BI) and a biological indicator evaluator resistometer (BIER) with ethylene oxide gas sterilization. The results indicate that the SMCP was not consistently less accurate than the LSKP in determining D10.

Colony Count, Microbial↗

PubMedDate not supplied

The relative safety of gamma-ray, autoclave, and ethylene oxide gas sterilization of thermosetting polyurethane.

Sterilization of polyurethane (PU) produces 4,4'-methylenedianiline (MDA), a known carcinogen, and various other compounds. The relationships of the components of PU to the formation of these compounds by sterilization were studied. Specimens of PU fabricated from different combinations of isocyanates and polyols were obtained from dialyzers. The molecular weight of the particular polyol was found to influence the production of MDA by sterilization. Sterilization also produced many unidentified compounds. MDA production was not always associated with the production of the other compounds. Compared with gamma-ray irradiation and ethylene oxide gas (EOG) sterilization, autoclave sterilization eluted more hydrophilic compounds. This phenomenon was significant for PUs produced from smaller-molecular-weight polyols. The combination of autoclave sterilization and a PU produced from a larger-molecular-weight polyol is recommended to minimize the production of potentially toxic compounds. Of the techniques studied, EOG sterilization produced the least amounts of MDA and the other compounds, but the residue of EOG is itself problematic. The risk posed by the amounts of MDA extracted was not significant, but the biological safety of the other compounds remains to be determined.

Aniline Compounds↗

PubMedDate not supplied

Factors in the preparation of biological indicators that affect the decimal reduction time.

The ISO 11138 series on biological indicators (BIs) lacks concrete specifications of the suspension, carrier material, and culture medium optimal for the preparation of the microorganisms. The suspension and culture medium used are thought to influence the accuracy of decimal reduction time (D) values. Their combined effects have not been elucidated, but some individual effects of particular suspensions, carrier materials, and culture media have been reported. Contrary to these reports, however, the author did not find such individual effects in a study of D values obtained using distilled water or saline as the suspension solution, paper or cotton yarn as the carrier material, and soybean casein digest (SCD) broth or agar as the culture medium. The study demonstrated that the combined effect of salt in the suspension during drying and the entrapment of microorganisms in salt crystal by pores in the cotton yarn carrier material increased microorganism resistance. D values also differed depending on the culture medium. Further investigation is needed to establish the optimal culture medium for BI microorganisms.

Ampholyte Mixtures↗

PubMedDate not supplied

The use of two or more microorganisms versus one microorganism in the carrier materials for biological indicators.

Specification for the preparation of a biological indicator (BI) using two or more microorganisms in the carrier material were deleted from the current ISO 11138 series and Working Draft 14161 because it was assumed that the resistances of the individual microorganisms would be affected by interference from the other microorganisms. This assumption is speculative only, and has not been supported by experimental evidence. To test its validity, the author carried out an experiment to determine the resistances of Bacillus subtilis and Bacillus stearothermophilus when used alone and together in BI carrier material. In total concentrations of 10(6) cfu/0.1 mL, the organisms were applied alone and together to filter paper and dried. After incorporation into the BI, the three preparations (B. subtilis alone, B. stearothermophilus alone, and both together) were subjected to ethylene oxide sterilization or to moist-heat sterilization using the procedures described in ISO 11138-2 or ISO 11138-3, respectively. Resistances were measured in terms of decimal reduction times (D values). The D values of the preparations were determined using the survival-curve method and the limited Spearman-Karber method in conjunction with a BI evaluator resistometer. The D values of the preparations did not differ significantly with either sterilization method, providing experimental evidence that, at least under these conditions, the presence of a second microorganism in the carrier material did not interfere with the resistance of the original microorganism.

Bacillus subtilis↗