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Biomedical subjects

H Shintani

Publications and source records attributed to H Shintani.

At least 55 records · Page 3Linked to original sources
PubMed1995

Formation and elution of toxic compounds from sterilized medical products: methylenedianiline formation in polyurethane.

The formation of a toxic and carcinogenic compound, methylenedianiline (MDA), in sterilized medical use polyurethane (PU) is discussed. Due to good biocompatibility and biostability, PU is widely used for blood-containing devices. There are two types of PU currently available for medical use. One is chain-extended thermoplastic PU, the other is thermosetting PU used for potting material connecting fibers and modules in artificial dialyzers and plasma separators. Both gamma-ray irradiation and autoclave sterilization are predominantly used for the sterilization of these devices. MDA formation in sterilized PUs by gamma-ray irradiation and by autoclave treatment is compared. The Delany clause in the USA prohibits the manufacture of medical devices producing any toxic compound during fabrication and sterilization, therefore, the formation and elution of MDA and other toxic compounds should be seriously considered. Although MDA formation at a concentration of a few to a few hundred ppb in autoclaved chain-extended thermoplastic PU has been reported, there have been no papers describing MDA formation in autoclaved thermosetting PU potting material, or describing MDA formation in gamma-ray irradiated chain-extended thermoplastic PU and thermosetting PU. We elected to determine whether MDA was in fact produced in Pus sterilized by gamma-ray irradiation or by autoclave sterilization. Our objective was to estimate the risk factor to the human patients or recipient. Our conclusion is to confirm which sterilization of gamma-ray or autoclave is more appropriate. No formation of MDA was observed in autoclaved thermosetting PU potting material at 121 degrees C for 60 min. A few ppm of MDA was formed in irradiated potting material. MDA formation increased with increasing irradiation doses. MDA formed in irradiated potting material at 2.5 Mrad (less than one ppm) is not a significant risk to the recipient. The estimated cancer causing risk factor when absorbing one mg MDA/kg body weight/day is 0.29. Twenty-nine persons per 100 persons exhibit a cancer potential. More importantly, our experimental evidence indicated that serum extracts from irradiated potting material contained unknown compounds other than MDA. The presence of these compounds is considerably more significant and toxic. When tested, these compounds proved to be mutagenic in the absence of metabolic activity, thus promoting a need to identify and study further. Compounds indicating mutagenicity increased with increasing irradiation. Small amounts of mutagenic compounds were determined in extract from autoclaved potting material, smaller than that by gamma-ray irradiation. Therefore, autoclave sterilization is more appropriate, providing materials can withstand the process.(ABSTRACT TRUNCATED AT 400 WORDS)

Aniline Compounds↗
PubMed1995

[Suture annuloplasty for mitral regurgitation with modified Paneth-Burr's method].

Plication of the leaflets or chordae reconstruction combined with annuloplasty cave been the standard procedure of the mitral valve repair for mitral regurgitation (MR). We have chosen the JH Kay's method for mitral annuloplasty. However, the long term results were not necessarily satisfactory because of various types of the mitral lesions. We have adopted the semicircular suture annuloplasty (Paneth-Burr's method) as the first choice for MR since May, 1991. In this paper, we demonstrate our modified operative procedure of the Paneth-Burr's method and the operative results. Also, to decide the optimal size of the annulus after annuloplasty, we evaluated the changes in size of the annulus and extent of mitral regurgitation before and about 16.3 months after surgery in 21 patients (pts) with MR undergoing Paneth-Burr's method, using Doppler echocardiography. On this annuloplasty, a double suture of EPTFE string (GORE-TEX) guarded with plegets was placed at the margin of the central fibrous body, sutured circumferentially around the annulus. Two rows of the suture were crossed in every several stitches to prevent cutting. A second suture was placed on the opposite side of the annulus in the same fashion. The MR patients were divided, by their size of the annulus after annuloplasty, into group A (less than 90% of normal annular diameter, 15 pts) and group B (more than 90% of normal annular diameter, 6 pts). In 14 of 15 pts of group A, mitral regurgitation was improved from grade 2-4 to grade 0-1 postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Relation of impaired left ventricular function in mitral regurgitation to left ventricular contractile state after mitral valve replacement.

To reevaluate the postoperative contractile state and survival, 34 patients (19 men and 15 women; average age 45 years, range 23 to 65) undergoing conventional mitral valve replacement between 1980 and 1990 were studied. There were 5 cardiac deaths (2 early and 3 late). Four of 5 deaths occurred in patients who had a preoperative left ventricular end-systolic volume index > 100 ml/m2. Sixteen patients with an end-systolic volume index < 100 ml/m2 (group I), and 5 with an index > 100 ml/m2 (group II) underwent repeat catheterization 8 months (range 4 to 17) after surgery. The ratio of end-systolic wall stress to end-systolic volume index increased significantly after surgery in group I, whereas it remained reduced in group II. The postoperative end-systolic wall stress/volume index ratio correlated significantly with the preoperative end-systolic volume index (p < 0.001). In the relation between end-systolic wall stress and ejection fraction, all patients in group II had values that were less than the 95% confidence limits for the normal relation. In conclusion, patients with a preoperative end-systolic volume index > 100 ml/m2 appeared to be at high risk of incurring irreversible depressed myocardial contractility, with a high postoperative mortality.

Adult↗
PubMed1994

Studies on dental high-speed cutting with carbide burs used on bovine dentin.

Bovine dentin was cut by hand with carbide burs and two cutting procedures while the rotational handpiece speed and the applied load were simultaneously monitored. It became evident that the maximum applied load during intermittent cutting varied from approximately 30 to 40 gm, whereas that during successive cutting ranged from approximately 20 to 60 gm. It showed that intermittent cutting produced a greater cutting effectiveness (for example, cutting volume per cut contact time) when carbide burs were used on dentin, compared with continuous cutting. It is recommended that the intermittent cutting procedure be used during work on patients.

Analysis of Variance↗
PubMed1994

Effect of polylactic acid on osteoinduction of demineralized bone: preliminary study of the usefulness of polylactic acid as a carrier of bone morphogenetic protein.

To evaluate the usefulness of polylactic acid (PLA), a bioabsorbable and plastic polymer, as a carrier of bone morphogenetic protein (BMP), a preliminary study has been carried out to investigate any negative effect of PLA on osteoinduction of demineralized bone (DB). PLA (10,600 mol. wt) was mixed with DB particles (1-1.5 mm square) prepared from rat femurs and laid subcutaneously on the intercostal muscle of 4-week-old Wistar rats. The PLA/DB pellets were harvested at 2, 4, 8 and 24 weeks after the operation, and prepared for light microscopic examination. Histological examination revealed cartilage formation at 2 weeks and new bone formation at 4 weeks. Extensive bone and marrow formation were observed at 24 weeks. PLA was gradually absorbed and completely disappeared at 24 weeks to be replaced by connective tissue. These results demonstrate that PLA does not have a negative influence on the osteoinductive activity and that PLA could well be a promising bioabsorbable carrier of BMP.

Animals↗
PubMed1994

Effects of aerosol administration of a thromboxane receptor antagonist (S-1452) on experimental asthma in guinea pigs.

The importance of thromboxane A2 (TXA2), one of the arachidonate metabolites, in the pathogenesis of bronchial asthma has been emphasized recently. Because aerosolized administration of antiasthmatic drugs is effective and safe, this study examined the effect of aerosolized TXA2 receptor antagonist (S-1452) on allergic bronchoconstriction in passively sensitized and mechanically ventilated guinea pigs. Under the cover of antihistamine, antigen-induced bronchoconstriction was markedly inhibited by pretreatment with aerosolized S-1452 inhalation in a dose-dependent manner. Although aerosolized S-1452 itself provoked weak bronchoconstriction for its partial agonist effect, bronchial responsiveness to inhaled histamine did not change 10 min after S-1452 inhalation. These results indicate that aerosolized S-1452 may be useful in treating bronchial asthma.

Aerosols↗
PubMed1994

Influence of filling on left ventricular diastolic pressure-volume curve during pacing ischemia in dogs.

The reversible upward shift of the diastolic pressure-volume curve that occurs during pacing-induced ischemia has not been fully explained by increases in passive chamber stiffness or reductions in relaxation rate. We measured the fully relaxed pressure-volume relation defined by both filling and nonfilling beats and the isovolumic relaxation time constant in nonfilling beats before and during demand ischemia using our in situ left ventricular volume clamping technique in 10 dogs. Pacing-induced ischemia shifted the diastolic pressure-volume curves in filling beats upward compared with the end-diastolic pressure-volume relation of the normally perfused heart. In contrast, the end-diastolic points for nonfilling beats during pacing-induced ischemia fell on the fully relaxed pressure-volume relation defined by the normally perfused heart. Left ventricular filling per se was necessary for the upward shift of the diastolic pressure-volume curve observed during pacing-induced ischemia. We speculate that active force developed during diastole induced by stretch activation or, perhaps, length-dependent changes in calcium sensitivity of the myofilaments in the ischemic myocardium due to stretch of the myocardium during rapid diastolic filling may contribute to the upward shift of the diastolic pressure-volume curve observed during pacing-induced ischemia.

Animals↗
PubMed1994

Inhibitory effect of aerosol administration of a sulfidopeptide leukotriene antagonist on bronchoconstriction induced by antigen inhalation in guinea pigs.

The effects of inhalation of the sulfidopeptide leukotriene antagonist AS-35 (9-[(4-Acetyl-3-hydroxy-2-n-propyl-phenoxy)methyl]-3-(1H- tetrazol-5-yl)-4H-pyrido [1,2-a]pyrimidin-4-one, CAS 108427-72-1) on bronchoconstriction induced by aerosol antigen, histamine, and leukotriene C4, D4 (LTC4, D4) were investigated in anesthetized and artificially ventilated guinea pigs. The increase in pressure at the airway opening (P(ao)) was measured as an index representing the grade of bronchial response. The bronchoconstriction induced by aerosol antigen was suppressed dose-dependently by pretreatment with inhaled AS-35 (0.1 mg and 1 mg) through a pressurized meter-dosed inhaler in the passively sensitized animals pretreated with diphenhydramine hydrochloride. But the histamine-induced bronchoconstriction was not altered by the pretreatment with AS-35 inhalation. On the other hand, LTC4- and LTD4-induced bronchoconstriction was inhibited by the pretreatment with aerosol AS-35 in a dose-dependent manner. The deposited dose of inhaled AS-35 in the peripheral airways was 3.5 micrograms and 6.5 micrograms when 0.1 mg and 1 mg of the drug was inhaled, respectively. These results suggest that sulfidopeptide leukotrienes (s-LTs) play an important role in the allergic bronchoconstriction in guinea pigs pretreated with antihistamine, and AS-35 inhalation may be beneficial in the treatment of asthma.

Administration, Inhalation↗
PubMed1994

[Reoperation for valvular heart diseases].

To elucidate the limitation of mitral valve reconstruction, 53 mitral disease patients (Mitral stenosis: 29, Mitral regurgitation: 24) undergoing reoperation late after valve reconstruction were studied, taking account of valvular lesions at initial operation. Reoperation rate after open mitral commissurotomy for mitral stenosis was higher in the patients with valvular regurgitation at initial operation than in those with severe subvalvular lesions or calcified valve. Reoperation rate for mitral regurgitation after mitral valvuloplasty was higher in the patients with stenotic fibrous degeneration or dilated annulus at initial operation than in those with torn chorda. Thus, these findings suggest that combined lesion of stenosis and regurgitation at initial operation may affect the reoperation rate in patients undergoing mitral valve reconstruction for either mitral stenosis or mitral regurgitation. Different approaches to the mitral valve through the left atrium and various techniques of the atriotomy have been practiced according to the need for a particular patients. The left atrium and the mitral valve can be exposed through median sternotomy followed by biatrial atriotomy or transplant approach. A correct approach and good exposure plays a key role in the success of redo surgical procedure for mitral valve disease.

Humans↗
PubMed1993

A pilot study of exposure of the smear layer to tannic acid solutions.

This study examined the effects of tannic acid on smear layer removal. Class V cavities were prepared on the buccal surfaces of extracted human molars with a No. 1557 high-speed carbide bur under water cooling for cutting and a No. 701 low-speed steel bur for finishing. They were then washed with water followed by an application of 2%, 5%, 10%, 15%, 20%, or 25% tannic acid solution in water for 15, 30, or 60 seconds. The axial wall dentin surfaces were examined with scanning electron microscopy. This examination showed that an application of 2% tannic acid for 60 seconds or 5% tannic acid for 15, 30, or 60 seconds effectively removed the smear layer, leaving the dentinal tubules occluded. The dentinal surfaces treated with 40% phosphoric acid for 15 seconds showed many exposed dentinal tubules with flared orifices.

Acid Etching, Dental↗
PubMed1993

Effects of post-curing by heat on the mechanical properties of visible-light cured inlay composites.

The aim of this study was to evaluate the effects of post-curing by heat on the mechanical properties of visible-light (V-L) cured three inlay composites and three posterior filling composites. One group was only photo-cured according to the manufacturers' recommended methods, while the other group was heat-treated at 100 degrees C for 15 min following initial cure by V-L. Knoop hardness, diametral tensile strength and compressive strength were measured to evaluate the mechanical properties. Cure performance was checked out by the solvent immersion test. Upon secondary-curing by heat, it was confirmed that the mechanical properties of the composites were increased moderately and the cure performance of the composites was also improved.

Composite Resins↗
PubMed1993

Effect of disrupting the mitral apparatus on left ventricular function in dogs.

BACKGROUND: The importance of the mitral apparatus to left ventricular function has been suggested in clinical studies. The effect of disruption of the mitral apparatus on left ventricular diastolic and systolic properties has not been fully documented. METHODS AND RESULTS: We investigated the end-diastolic and end-systolic pressure-volume and stroke work-end-diastolic volume relations and measured the isovolumic relaxation time constant (tau infinity) during nonfilling beats before and after disruption of the mitral apparatus under different loading conditions in 14 dogs using our recently developed volume-clamping technique for the in situ left ventricle. Disruption of the mitral apparatus increased left ventricular diastolic equilibrium volume (V0d) without changing the slope of the end-diastolic pressure-volume relation (Sd) and increased end-systolic pressure-volume relation dead volume (V0s) and volume-axis intercept of stroke work-end-diastolic volume relation (V0sw) without changing the slopes of these relations (maximum elastance, Ees, and Ssw). Disruption of the mitral apparatus increased tau infinity. CONCLUSION: Disruption of the mitral apparatus increases the equilibrium volume without changing left ventricular diastolic stiffness or contractility and slows left ventricular relaxation. These results support and help explain the clinical observation that it is desirable to maintain the mitral apparatus during mitral valve replacement surgery.

Animals↗
PubMed1993

[Heart failure in valvular heart disease].

The clinical manifestations of heart failure depend importantly on the rate at which the syndrome develops and specifically on whether sufficient time has elapsed for compensatory mechanisms to become operative and for fluid to accumulate in the interstitial space. In most cases of the valvular heart diseases, patients survive the acute insult, and anatomical and functional abnormalities of the valves develop gradually, so that a host of compensatory mechanisms develop, especially cardiac hypertrophy. These allow the patient to adjust to and tolerate not only the anatomical abnormalities, but also a reduction in cardiac output or changes in loading condition, with less difficulties. The most important goal of treatment for the patients with chronic heart failure is to improve prognosis and the quality of life. Surgical correction is one of the best way to obtain good results in the treatment of the valvular heart diseases. We have been evaluated left ventricular pump function and contractile function before and after surgery for valvular diseases using the method for estimating myocardial contractility, that is, the relationship between ejection fraction and end-systolic volume or a ratio of end-systolic wall stress to end-systolic volume (ESS/ESVI), estimated the reversibility of the left ventricular systolic function after surgery, and determined the timing of operation. To make precise evaluation for the heart failure in patients with chronic valvular heart diseases, particularly during compensatory period, reduced pump function and myocardial contractility rather than clinical symptoms should be assessed and considered as an indicator for severity of the heart failure.

Aortic Valve Insufficiency↗
PubMed1992

Difference in tumor incidence and other tissue responses to polyetherurethanes and polydimethylsiloxane in long-term subcutaneous implantation into rats.

The long-term (1- and 2-year) adverse tissue responses including tumor formation by subcutaneous implantation of polyurethanes (PUs) and silicone (Sil) films into rats were compared. The weight-averaged molecular weights (Mw) of the PUs prepared from 4,4'-diphenylmethanediisocyanate, poly(tetramethyleneglycol) of Mn = 1000 and 1,4-butanediol are 220,000 (U-4), 124,000 (U-6), and 55,600 (U-8). The 50:50 mixed film of U-6 and silicone (U-6/sil) was prepared by roll-mixing of the noncured silicone and the U-6 solution followed by evaporation of the solvent and heat-curing at 70 degrees C. The tissue responses around implants were classified into four groups as follows: (A) tumor, (B) atypical cell proliferation accompanied by preneoplastic changes, (C) cell proliferation without preneoplastic changes, (D) no obvious responses. In both implantation periods, the PUs gave higher incidents of the adverse responses including tumor formation in comparison to Sil. No significant molecular weight-dependent trend was found in a 1-year study using U-4, 6, and 8. Significant PU-dose-dependent trends were found in a 2-year study: the total active incidence (A+B+C), U-6(22/29) greater than U-6/sil(11/29) greater than sil(7/28); tumor incidence (A), U-6(11/29) greater than U-6/sil(2/29) = sil(2/28). No detectable amounts of 4,4'-methylenedianiline (MDA) were found in the PUs. The methanol extracts from the PUs were negative in the mutagenicity tests. These indicate no relationship between the tumor formation by the PU films and the mutagenicities of the chemicals (mainly oligomers) leached from the PUs.

Aniline Compounds↗
PubMed1992

Characterization of inorganic fillers in visible-light-cured dental composite resins.

Inorganic fillers in seven visible-light (VL)-cured dental composite resins were examined for their size, composition, phase and content, employing the following analytical instruments. SEM observations indicated that five samples could be classified into the hybrid type while the remaining two belonged to micro-filled and sub-micron types. EDX analyses revealed that five samples contained BaO while others lacked BaO. XRD analyses showed that three were in vitreous phase, two were in the crystalline phase and two were mixtures of both. DTG thermal analyses indicated that the hybrid type composites had the higher inorganic filler content (wt%) than the composites of two other types. In conclusion, wide varieties exist in the inorganic fillers in VL-cured dental composite resins currently utilized.

Aluminum Oxide↗
PubMed1992

In-vitro and in-vivo wear profile of composite resins.

The aim of this study was to evaluate in-vitro wear by two types of slurry of 10 commercial composite resin materials (seven hybrid and three microfilled composites). There was great variation in the in-vitro wear pattern by two types of slurry. The wear rate of microfilled composites was greater than that of hybrid composites, and a negative correlation was observed between wear rate and Knoop hardness values among all materials when hydroxyapatite slurry was used. In contrast, the wear rate of hybrid composites was greater than that of microfilled composites when abraded by green carborundum slurry. These abraded surfaces were compared with SEM micrographs of in-vivo composites surface after 4 years of service. The profile of in-vivo wear surfaces was found to be similar to that of in-vitro wear surfaces abraded with hydroxyapatite slurry.

Composite Resins↗