Study of rationalized safety design based on the seismic PSA for an LMFBR

Seismic PSA was carried out for a typical liquid metal cooled fast breeder reactor (LMFBR) in order to study the rationalized seismic design, maintaining and/or improving safety during seismic event. The seismic sequence quantification identifies the dominant structures, systems and components (SSCs) to the seismic core damage frequency (CDF). The sensitivity analyses by reducing or increasing the seismic capacity for SSCs are used to examine the optimized seismic design in view of safety and economical aspects. The LMFBR-specific risk-significant SSCs are reactor coolant boundary, decay heat removal coolant path and reactor control rod, which are different from those of light water reactors (LWRs). The electrical power supply system has a minor contribution to the seismic CDF. The sensitivity study shows that passive safety features of LMFBRs are important to maintain and/or enhance seismic capacity. The passive safety includes the decay heat removal capability via natural circulation and safety measures without depending on the support systems such as alternating current (AC) electrical power, for example. On the course of seismic sequence quantification, a methodology to evaluate the probability of seismic-induced multiple failure has been developed and applied to the decay heat removal function. The results suggest the multiplicity of the triply redundant system is to be considered for the significant components such as the decay heat removal path when one considers the difference in the seismic response.     

Low Serum Parathyroid Hormone Is a Predictor of Early Death after Hip Arthroplasty in Hemodialysis Patients

Background and Purpose:  Colloid osmotic pressure (COP) in plasma rises by ultrafiltration during hemodialysis, and it consequently causes plasma refilling in which water moves from interstitial tissue to capillary space. Although hemodynamic stability is one of the important factors for good dialysis outcome, no informative and convenient indicators are available other than monitoring of blood pressure. Thus, we measured COP during hemodialysis whether COP can be used as an indicator for the hemodynamic status in comparison with hematocrit (Ht). Plasma osmolality, ultrafiltration volume, and the alteration of blood pressure were also measured to examine whether COP is associated with them.
Method:  Sixteen patients hospitalized in this hospital were examined. Amongst them, 10 patients underwent both dialysis and ultrafiltration, while 4 patients received only dialysis and 2 patients were with ultrafiltration only by extracorporeal ultrafiltration method. Ultrafiltration was performed with constant speed to the dry weight for 4 h. The measurements of COP, plasma osmolality, Ht levels, and blood pressure were performed at 30 min (12.5% of the total water removal), 1 h (25%), 2 h (50%), and 3 h (75%) after the start of hemodialysis and also at the end of dialysis (100%).
Result:  COP markedly rose by 26.0% (±13.3%) in the patients who received both dialysis and ultrafiltration, whereas Ht rose by only 13.6% (±5.21%). And the curve for COP increase was sigmoid shape, whereas that for Ht showed linear change. On the other hand, in the patients whose Ht levels showed low values, the curves for both COP and Ht showed similar pattern.
Conclusion:  These results suggest that COP is a more sensitive indicator to be monitored for the hemodynamic status than Ht during hemodialysis.     

Thoracic arachnoid cyst presenting incomplete features of Brown-Séquard syndrome: a case report

Spinal intradural arachnoid cyst presenting incomplete features of Brown-Séquard syndrome is very rare. Only 6 cases have been reported. We report one in a thoracic lesion. A 42-year-old man noticed thermohypesthesia in his right leg, and monoparesis in his left leg. On admission, he presented incomplete features of Brown-Séquard syndrome below the Th7 level. MRI showed the spinal cord to be displaced antero-laterally to the right at Th6-7 level. Myelography and CT myelography failed to show the cyst wall, but an arachnoid cyst was totally removed with T5-8 osteoplastic laminotomy. Sensory disturbance has not changed postoperatively, but motor weakness in his left leg recovered within one month after the operation. No cystic lesion has been detected by MRI during the ten months since the operation. We investigated all seven cases in the literature including our case which showed incomplete features of Brown-Séquard syndrome. As regards to the location of the cyst, all cases were at the mid-thoracic level. And four cases were at the midline. These results suggest that the mechanism of Brown-Séquard syndrome associated with spinal arachnoid cyst may be related not only to the laterality of the lesion but also to the asymmetrical circulation in the watershed area.     

Effect of methylmercury on the ethanol elimination from the blood and the activity of alcohol dehydrogenase

In an attempt to assess the effects of methylmercury on ethanol metabolism, Sprague-Dawley rats were treated with a daily dose (10 mg/kg i.p.) of methylmercuric chloride for 2 consecutive days and given a test dose (0.4 g/kgi.v.) of ethanol 24 hr after the last treatment. Blood ethanol levels were measured using gaschromatography by the direct introduction of blood samples into the sample vaporizing apparatus attached to the chromatograph. While treatment with methylmercury elicited a slight retardation in the ethanol elimination from the blood during 30 to 90 min, methylmercury did not essentially alter ethanol metabolism. There was no significant change in hepatic alcohol dehydrogenase activity of methylmercury-treated rats. By contrast, the activity of alcohol dehydrogenase purified from liver or yeast was remarkably inhibited by methyl-mercury and the type of inhibition proved to be non-competitive. Moreover, the inhibited activity was reactivated easily by sulfhydryl agents. From these results, it is conceivable that methylmercury has little influence on ethanol metabolism in vivo because of its non-specific binding with sulfhydryl groups in the organism.     

Competitive amino acid transport between L-tryptophan and other amino acids in Schizophyllum commune

In our study on nutritional requirement for the hyphal growth of Schizophyllum commune, we found that a Trp- mutant could not grow in the L-Trp-supplied medium in the presence of L-Ser. Further growth studies showed that not only L-Ser but also as many as 11 kinds of amino acid including L-Ala, L-Arg, L-Asn, L-His, L-Leu, L-Met, L-Phe, L-Ser, L-Thr, L-Tyr and L-Val inhibited the growth of the Trp- mutant in the L-Trp-supplied medium. However, these amino acids did not inhibit the growth of a Trp+ strain. The inhibition of growth of Trp+ strain induced by a Trp analogue of 5-fluoro-DL-tryptophan (5FT), which was usually recovered by L-Trp, was rescued by the same amino acids mentioned above. The exceptions were Gly and L-Ile, which also recovered the growth inhibition induced by 5FT. These results indicate that the permease responsible for the Trp transport in S. commune might also be active to other amino acids. However, it is considered that the permease shows high affinity to L-Trp and low affinity to other amino acids. As a result, the transport of L-Trp and 5FT may be counteracted by other amino acids.