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The Fukushima Daiichi Nuclear Power Plants (1FNPPs) are thought to be subcritical, but the condition will be changed during the fuel debris retrieval. Subcriticality control is one of the most impo...

The repeated-dose liver micronucleus assay has the potential to detect liver carcinogens and could be integrated into general toxicological studies. To assess the performance of this assay, kojic acid was tested in 14-day and 28-day liver micronucleus assays. We evaluated the incidence of micronucleated cells in liver, bone marrow and peripheral blood and performed comet assays in both the liver and peripheral blood (comet assay was performed only for 14-days). Kojic acid, a skin-whitening agent used in cosmetic products, was orally dosed in six-week-old male rats at 250, 500 and 1000mg/kg/day for 14 days, and at 125, 250 and 500mg/kg/day for 28 days. Organ weight and histopathology were examined at the end of the experiment. Neither a clear, positive response in micronucleus (MN) incidence nor changes in the percent of tail DNA in the comet assays was noted in liver and bone marrow. An increase of relative liver weight was observed in 1000mg/kg/day for 14 days. In histopathology, minimal hypertrophy of hepatocytes was found at 1000mg/kg/day for 14 days. The results of both the micronucleus assay and the comet assay indicate that 14-day and 28-day repeated dosing of kojic acid are non-genotoxic in the liver and bone marrow. Kojic acid has been known to act as a tumor-promoter in thyroid carcinogenesis but has not been shown to have initiation activities in liver carcinogenesis. Findings in this study are consistent with the evidence that kojic acid is not an apparent initiator of liver carcinogenesis. Therefore, the liver micronucleus assay is simple and sensitive to detect genotoxic liver carcinogens.

We aimed to reveal the prevalence and pattern of human papillomavirus (HPV) infection and p53 mutations among Japanese head and neck squamous cell carcinoma (HNSCC) patients in relation to clinicopathological parameters. Human papillomavirus DNA and p53 mutations were examined in 493 HNSCCs and its subset of 283 HNSCCs. Oropharyngeal carcinoma was more frequently HPV-positive than non-oropharyngeal carcinoma (34.4% vs 3.6%, P < 0.001), and HPV16 accounted for 91.1% of HPV-positive tumors. In oropharyngeal carcinoma, which showed an increasing trend of HPV prevalence over time (P < 0.001), HPV infection was inversely correlated with tobacco smoking, alcohol drinking, p53 mutations, and a disruptive mutation (P = 0.003

This paper proposes a noninvasive method for estimating the viscoelastic characteristics of arterial walls using pulse waves measured in various parts of the body using a foil-type pressure sensor (FPS) and a photoplethysmogram. The FPS was employed to measure pulse waves based on the tonometry approach for its characteristics of high sensitivity and flexibility as well as its ability to continuously measure the alternating-current component of pulse waves. First, in order to accurately measure the amplitude variation of blood pressure waves, suitable mechanical forces externally applied to the FPS were examined, and it was found that values of 5 - 25 (N) yielded the best performance. Next, to verify the time characteristics of pulse waves, the brachial-ankle pulse wave velocity (baPWV) was measured. The results showed that baPWV determined using the FPS and that found with a noninvasive vascular screening device were almost the same. Estimation was then performed to establish arterial viscoelastic indices for the radial artery and the dorsal pedis artery during the application of mechanical pain stimuli. The results suggested that the estimated indices could be used to quantitatively assess vascular response caused by sympathicotonia. Thus, it was concluded that the proposed method enabled noninvasive measurement of pulse waves and estimation of viscoelastic indices.

Glucocorticoids, such as dexamethasone, have been used as in vitro inducers of adipogenesis. However, the roles of the glucocorticoid receptor (GR) in adipogenesis have not been well characterized yet. Here, we show that inhibition of GR activity using the GR antagonist RU486 prevents human mesenchymal stem cell and mouse embryonic fibroblast (MEF) differentiation into adipocytes. Moreover, in MEFs isolated from GR knockout (GR(null)) and GR(dim) mice deficient in GR DNA-binding activity, adipogenesis was blocked. We identified glucocorticoid response element sites in the first intron of KLF15 by bioinformatical promoter analysis and confirmed their functional relevance by demonstrating GR interaction by chromatin immunoprecipitation. Moreover, transfection of MEFs with siRNA for KLF15 significantly attenuated the expressions of adipogenic-marker genes and the lipid accumulation. Our results provide a new mechanism for understanding glucocorticoids-dependent adipogenesis and that GR promotes adipogenesis via KLF15 gene expression as a transcriptional direct target.

This paper proposes a noninvasive method for estimating the dynamic characteristics of arterial walls using pulse waves measured in various parts of the body by a foil-type pressure sensor. The sensor not only has high sensitivity and flexibility but also features the ability to continuously measure the alternating-current component of pulse waves. These capabilities make it suitable for estimating the dynamic characteristics of arterial walls. In this paper, a foil-type pressure sensor was employed to measure pulse waves based on the tonometry approach, and a method of estimating changes in arterial viscoelastic indices was proposed based on the measured pulse waves and photoplethysmograms. In order to accurately measure blood pressure, first, we examined suitable mechanical forces to the sensor, and found that values of 5-25[N] yielded the best performance. We then estimated the arterial viscoelastic indices of a radial artery and a dorsal pedis artery when mechanical pain stimuli were applied to the subjects. The results suggested that the estimated indices can be used to quantitatively assess vascular response caused by sympathicotonia. We thus concluded that the proposed method enabled noninvasive measurement of pulse waves in the dorsal pedis artery and estimation of arterial viscoelastic indices.

目的: 全部床義歯補綴臨床における画像診断法としての規格撮影パノラマX線写真透写図分析法に用いる, ポリゴン表の適切な計測基準点および標準値について検討すること.方法: 若年有歯顎者と新義歯装着直後の全部床義歯装着者を被験者とし, 規格撮影パノラマX線写真透写図上の解剖学的指標に基づき, 補綴臨床で重要な咬合高径や咬合平面に関する角度ならびに距離計測を行った. これら若年有歯顎者と全部床義歯装着者の計測値の平均値について, 一元配置分散分析と多重比較を用いて統計学的に分析した. さらに, 男女各1名の無歯顎患者の新旧義歯の評価に, 今回作製した全部床義歯装着者の男女別データを標準値とするポリゴン表の利用を試みた.結果: 計測値には, 若年有歯顎者と全部床義歯装着者ともに男女間, 男女ともに若年有歯顎者と全部床義歯装着者間で有意差を示したものがあった. また, 咬合平面は, 後方基準として耳珠上縁よりも下縁を用いたカンペル平面とより平行であった. さらに, 今回計測した全部床義歯装着者の計測値を標準値としたポリゴン表は, 無歯顎患者の咬合平面や咬合高径の評価に利用できることが示唆された.結論: 男女別の全部床義歯装着者の計測値を標準値として用いた, ポリゴン表による規格撮影パノラマX線写真透写図分析法は, 無歯顎患者の義歯を評価できることが示唆された.

A novel direct calculation method of response matrices on heterogeneous lattices by using the Monte Carlo method is proposed. These direct response matrices (DRMs) can be used in core calculations in place of the conventional homogenized lattice constants. The DRMs are formalized by four sub response matrices (sub-RMs) in order to respond to a core eigenvalue, k; thus the DRMs can be re-evaluated on each outer iteration in the core calculations. The sub-RMs can be evaluated by analyzing each neutron's trajectory from ordinary lattice calculations with the Monte Carlo code. Since these sub-RMs are calculated directly under an actual complex assembly geometry, i.e., without a homogenization process, intra-assembly heterogeneous effects can be reflected on global partial current balance calculations. With using two of the sub-RMs, which deal with neutron production probabilities for each fuel pin, and the obtained partial current balance, pin-wise neutron production distributions can also be reconstructed. T...

The aim of this study was to compare different methods for effective adhesion between a glass fiber-reinforced composite (FRC) material for framework and a veneering composite (VC) material for coating framework when fabricating clasps (FRC clasp (with VC)). Vectris pontic and EG fiber were used as FRC materials, the glass fibers of which were preimpregnated with resin. Palfique estelite LV was used as the VC material.Laminate specimens were fabricated by coating FRC with VC (Palfique⁄Vectris, Palfique⁄EG fiber). Five adhesion methods were used when coating the framework. Three specimens were prepared for each adhesion methods. Deflection and load when VC cracked were examined using the three-point flexural test. The mean and S.D. of each value were calculated and subjected to two-way analysis of variance (ANOVA) and multiple comparisons (Bonferroni⁄ Dunn) to determine the significance of the differences (P = 0.05 and 0.01) between the results of the respective methods.The deflection of Palfique⁄Vectris and Palfique⁄EG fiber was 0.497-0.631 and 0.426-0.481 mm, respectively, the load of which was 92.33-108.00 and 60.17-72.50 N, respectively. The deflection and load under all adhesion methods were significantly higher in Palfique⁄Vectris than Palfique⁄EG fiber (P

The neurotoxin of strain 111 (111/NT) associated with type B infant botulism showed antigenic and biological properties different from that (Okra/NT) produced by a food-borne botulism-related strain, Okra. The specific toxicity of 111/NT was found to be about 10 times lower than that of Okra/NT. The monoclonal antibodies recognizing the light chain cross-reacted with both neurotoxins, whereas most of the antibodies recognizing the carboxyl-terminal half of the heavy chain of Okra/NT did not react to 111/NT. Binding experiments with rat brain synaptosomes revealed that 125 I-labeled 111/NT bound to a single binding site with a dissociation constant ( K d ) of 2.5 nM; the value was rather lower than that (0.42 nM) of 125 I-Okra/NT for the high-affinity binding site. In the lipid vesicles reconstituted with ganglioside GT1b, 125 I-Okra/NT interacted with the amino-terminal domain of synaptotagmin 1 (Stg1N) or synaptotagmin 2 (Stg2N), fused with the maltose-binding protein, in the same manner as the respective full-length synaptotagmins, and the K d values accorded with those of the low- and high-affinity binding sites in synaptosomes. However, 125 I-111/NT only exhibited a low capacity for binding to the lipid vesicles containing Stg2N, but not Stg1N, in the presence of ganglioside GT1b. Moreover, synaptobrevin-2, an intracellular target protein, was digested to the same extent by the light chains of both neurotoxins in a concentration-dependent manner. These findings indicate that the 111/NT molecule possesses the receptor-recognition site structurally different from Okra/NT, probably causing a decreased specific toxicity.

A core analysis system has been developed for the recent advanced designs of boiling water reactors. This system consists of a fuel assembly analysis code VMONT and a three-dimensional core simulat...

The multienrichment boiling water reactor (BWR) initial core design was first applied to the Kashiwazaki-Kariwa Nuclear Power Station Unit 5 [1100-MW (electric) BWR] in Japan. This core is designed to improve fuel discharge exposure, capacity factors, and operability. The design study shows that three types of fuel bundles with different enrichments are suitable to achieve the design targets. Three bundle enrichments are selected to simulate each of the following: fresh bundles, once-burned bundles, and twice-burned bundles in the reload core. Although the heterogeneity of multienrichment design increases the complexity of the design analysis, both the initial criticality test and the moderator temperature coefficient measurement showed good agreement with the prediction. Subsequent full-power operation verified the expected core performance. Average discharge exposure for the total initial fuel is {approximately}10% larger than that for the conventional single-enrichment BWR initial fuel with reinsertion of discharged fuel at the end of the first cycle. These experiences verified the effectiveness of a multienrichment initial core for the improvement of fuel utilization, capacity factors, and operability.

1. We examined the effects of a selective endothelin A (ETA)-receptor antagonist, BQ-123, on the development of hypertension and organ damage in stroke-prone spontaneously hypertensive rats (SHRSP) given 1% NaCl for 6 weeks. 2. BQ-123 at doses of 0.7, 2.1 and 7.1 mg/day was continuously administered for 6 weeks to 8 week old salt-loaded SHRSP, who were given water containing 1% NaCl for the following 6 weeks, via a subcutaneous osmotic minipump. 3. Development of high blood pressure was accelerated in salt-loaded SHRSP compared with that in non-salt-loaded SHRSP. After 6 weeks of salt-loading, incidence of cerebral infarction, renal sclerosis and renal fibrosis were greater in salt-loaded than non-salt-loaded SHRSP. 4. BQ-123 attenuated the age-related rise in blood pressure in a dose-dependent manner. The effect coincided with reduction in the incidence of cerebral infarction and prevention of renal sclerosis and fibrosis. Kidney function was improved as observed by an increase in glomerular filtration rate and decreases in urinary protein excretion, blood urea nitrogen and fractional sodium excretion. Furthermore, BQ-123 prevented increases in the heart weight/bodyweight ratio and aortic wall thickness in salt-loaded SHRSP. 5. These results suggest that endogenous endothelin-1 (ET-1) and ETA-receptors may be, at least in part, involved in the pathogenesis of hypertension and organ damage in salt-loaded SHRSP.

Localization and alteration of the levels of immunoreactive endotheoin-1 (ir-ET-1) products of canine basilar artery were examined in a one-hemorrhage model. Subarachnoid hemorrhage (SAH) was induced by a single injection of autologous arterial blood into the cisterna magna. In SAH dogs, the endothelial cells on day 2 showed minimal changes such as rounding nuclei or edema, and these injuries progressed on days 4 to 6 from moderate changes with subendothelial edema to severe damage characterized by denudation. In these dogs, ir-ET-1 products on endothelial cells were significantly enhanced and reached maximum levels on day 2 followed by gradual reduction on day 4 to 6. Although no significant changes appeared on endothlial cells in untreated dogs and control dogs on day 2 after the injection of saline, weak ir-ET-1 products were localized irregularly on those cells. However, ir-ET-1 levels on day 4 and 6 were significantly higher in SAH dogs than in untreated dogs. Cerebral arteries were covered with blood clots and a number of inflammatory cells had invaded the adventitia of basilar arteries, in addition to sorrounding the clots. The number of inflammatory cells and the quantity of ir-ET-1 products in the adventitia achieved maximum levels on day 2, and decreased on day 4 to 6. Almost all the inflammatory cells were positive for anti-macrophage antibody. Thus, the levels of ir-ET-1 products on endothelial cells were enhanced with minimal injury on day 2 and gradually decreased with the progression of the injury, while those in the adventitia correlated well with the number of macrophages migrating into the adventitia. These results suggest that ET-1 is derived mainly from macrophages migrating into adventitia as well as endothelial cells, and is an important factor for vasospasm after SAH, not only in the early phase but also in the late stages.

system to automatically generate re-startup plans for BWR plants has been developed. By including consideration of high speed re-startup after reactor shutdown, where xenon By including consideration of high speed re-startup after reactor shutdown, where xenon By including consideration of high speed re-startup after reactor shutdown, where xenon current reactor conditions. For this purpose, not only BWR core managing expertise in a knowledge base, but also core simulation programs are used. To realize both higher accuracy and shorter computing time of core characteristics predictions by the simulation programs, the error tendency between the simulation results and actual plant data is learned using an artificial neural network. To make the plan for re-startup operation, first, allowable xenon concentrations and corresponding control rod patterns that satisfy thermal constraints at the rated power are estimated. Secondly, based on the estimation results, control rod withdrawal sequence, reactor power, control rod pattern and core flow rate for each time are determined. A prototype system was developed to evaluate its performance. The system was capable of generating a plan automatically within 30min.

我が国の商業用軽水炉は,その優れた実績を背景に一層の安全性向上のみならず,廃棄物低減,経済性向上,原子燃料サイクルの確立といった多様な要求を満たすべく高度化の道を歩みつつあるそうした変化に対応するため,炉心設計技術も徐々に進化してきているが,本稿では,その基礎となる核計算手法の近年の高度化の動向について述べる。

The purpose of this study was to design an optimum glass fiber-reinforced composite (FRC) clasp. Three-dimensional finite element models were constructed of FRC circumferential clasp arms and an abutment tooth. The basic clasp arm was half-oval, without a taper, 2.60 mm wide and 1.30 mm thick. Four modified clasp arms were prepared by changing the width or thickness of the basic clasp (width/thickness: 2.60 mm/0.65 mm, 2.60 mm/1.95 mm, 1.30 mm/1.30 mm, and 3.90 mm/1.30 mm). Forced displacements of 5 mm in the removal direction were applied to the nodes at the base of the clasp arm. The retentive forces and maximum tensile stresses of the five FRC clasp arms ranged from 1.00–16.30 N and from 58.9–151 MPa, respectively. Results showed that an optimum FRC clasp was a circumferential clasp with 2.60 mm width and 1.30 mm thickness, which had sufficient retentive force and low risk of tensile failure.

This paper proposes a noninvasive method for estimating the dynamic characteristics of arterial walls using pulse waves measured in various parts of the body by a foil-type pressure sensor (FPS) and a photoplethysmography. The FPS not only has high sensitivity and flexibility but also features the ability to continuously measure the alternating-current component of pulse waves, and was employed to measure pulse waves based on the tonometry approach. Then a method of estimating changes in arterial viscoelastic indices was proposed based on the measured pulse waves and photoplethysmograms. First, in order to measure amplitude variation of the blood pressure wave shape accurately, we examined suitable mechanical forces externally applied to the FPS, and found that values of 5 – 25 [N] yielded the best performance. Next, in order to verify the time characteristics of the pulse waves, the brachial-ankle Pulse Wave Velocity (baPWV) was measured and found that baPWVs measured by the FPS and the noninvasive vascular screening device are quite similar. We then estimated the arterial viscoelastic indices of a radial artery and a dorsal pedis artery when mechanical pain stimuli were applied to the subjects. The results suggested the estimated indices could be used to quantitatively assess vascular response caused by sympathicotonia. We thus concluded the proposed method enabled noninvasive measurement of pulse waves and estimation of viscoelastic indices.

The purpose of this study was to investigate the effects of different cross-sectional shapes and presence of taper on stress distribution in clasp arms made of glass fiber-reinforced composite (FRC) material. Stress analysis of clasps was performed under a constant load (5 N) using a three-dimensional finite element method with due consideration to the anisotropy of unidirectional FRC material. Results were then compared with clasp arms made of metal- an isotropic material. It was found that both FRC clasps and metal clasps yielded similar results. As for the displacement of clasp arms with a basic cross-sectional shape under a load of 5 N, the amount of displacement showed that FRC clasps provided sufficient retentive force required for clinical application.

A nested polymerase chain reaction was utilized to successfully detect the type B botulinum neurotoxin gene of Clostridium botulinum in feces from a 6-month-old patient, who had already been diagnosed with type B infant botulism by mouse bio-assay. This method of rapid diagnosis without enrichment culture of feces can be applied to other types of toxins in the use of the type-specific primers. Further investigations, however, are required to define the sensitivity and specificity of the method.

Hepatocyte growth factor (HGF) is known to influence a number of cell types and their production of regulatory cytokines. We investigated the potential of recombinant HGF to regulate not only the development of allergic airway inflammation and airway hyperresponsiveness (AHR), but also airway remodeling in a murine model. Administration of exogenous HGF after sensitization but during ovalbumin challenge significantly prevented AHR, as well as eosinophil and lymphocyte accumulation in the airways; interleukin (IL)-4, IL-5, and IL-13 levels in bronchoalveolar lavage (BAL) fluid were also significantly reduced. Further, treatment with HGF significantly suppressed transforming growth factor-beta (TGF-beta), platelet-derived growth factor, and nerve growth factor levels in BAL fluid. The expression of TGF-beta, the development of goblet cell hyperplasia and subepithelial collagenization, and the increases in contractile elements in the lung were also reduced by recombinant HGF. Neutralization of endogenous HGF resulted in increased AHR as well as the number of eosinophils, levels of Th2 cytokines (IL-4, IL-5, and IL-13) and TGF-beta in BAL fluid. These data indicate that HGF may play an important role in the regulation of allergic airway inflammation, hyperresponsiveness, and remodeling.

金沢大学大学院医学系研究科病態検査学, We encountered a patient with infant botulism caused by a single clone of Clostridium botulinum type B. In the early convalescent phase, a C. botulinum type B-like nontoxigenic organism emerged in the feces instead. Growth inhibition of toxigenic strains by nontoxigenic strains was examined.

A six-month-old girl with a 5 consecutive day history of constipation and poor feeding developed generalized weakness, poor head control, difficulties in sucking and swallowing, and cranial nerve dysfunction within a few days. These characteristic manifestations and clinical course prompted examination of the possibility of infant botulism, although no history of eating honey was obtained. Mouse bioassay performed with enema effluent demonstrated type B botulinum toxin. Culture of the effluent was positive for Clostridium botulinum type B. This is the first case of type B infant botulism in Japan.

The Japanese Ministry of Health and Welfare is again considering legalization of steroid oral contraceptives. Approval could greatly reduce the incidence of abortion in Japan, which is at least twice that officially reported.

Disclosed is a sealed alkaline storage battery with an increased utilization of a positive electrode active material comprising a nickel oxide and with drastically enhanced capacity density. The positive electrode active material is a nickel based multi-metals oxide containing at least one element such as Mn, Al, Co, Cr, Fe, Zr and Bi which promotes the formation of γ phase during charging. The ratio A γ /A β of the integrated intensity A γ of the diffraction peak at d = about 7 angstroms attributed to the γ phase to the integrated intensity A β of the diffraction peak at d = about 4.5 to 5.0 angstroms attributed to the β phase of the oxide in the completely charged state is not smaller than 0.4. The electrolyte comprises an aqueous solution containing at least one of K + and Na + as a cationic component and the total concentration of the above-mentioned cationic component in the completely charged state is within a range between 4 and 12 mol/l.

A review was made on 63 cases (males: females=43:20) with various kinds of foreign bodies of the tracheobronchial tree treated mainly at the ENT Department of Hirosaki University and at the Central Hospital of Aomori Prefecture. The youngest among the 63 cases was 6 month-old baby boy and the eldest was 63 year-old male. Bronchoscopic removal of foreign bodies was carried out without general anesthesia on 21 cases who were seen before 1967, whereas since 1968, ventilation bronchoscopy under general anesthesia has been in use when necessary. Postbronchoscopic tracheostomy was necessitated in only 1 case.The 63 foreign bodies were classified into two categories, i. e. non-radiopaque and radiopaque, and the ratio was 45:18. Among the non-radiopaque foreign bodies, there were peanuts (24 cases), beans, seeds, corns or other vegetables (9 cases), pieces of meat (3 cases), plastic pencil cap (4 cases), plastic bullet of toy gun (2 cases), a part of plastic toy (2 cases) and celluloid pipe (1 case). Sixteen among the 24 cases with peanuts were under 2 years of age (males: females=11:5). The radiopaque foreign bodies were: needles (2 cases), drawing pin (2 cases), nail, single false tooth, head of ball-point pen, staple, screw of compass and dental reamer (1 case each). Among those, 2 staples located in the lingular division and a pin located in the right upper anterior bronchus (B3α) were removed under X-ray TV monitoring.

Nine 2-aminothiazolyl methoxyiminoacetamidocephems (ATOICs) as well as several 4-furyl methoxyiminoacetamidocephems (FOICs) were compared for stability to and inhibition of various β-lactamases. Although ATOICs are generally less stable to cefuroxymases (CXases) from Proteus vulgaris or Bacteroides fragilis, the relative susceptibility among them was greatly affected by the substitution at the 3-position : the compound unsubstituted at C-3 was most stable, while thiomethyleno-2-methyl-6-hydroxytriazine-5-one substitution gave the most labile compound. A similar tendency was also seen with FOICs, which, however, were in general more susceptible to those CXases than were ATOICs. The substitution at C-3 had lesser effects on the stability to some cephalosporinases (CSases), and also had little effect on the inhibitory activity of ATOICs and FOICs on various CSases, though the compound unsubstituted at C-3 (ceftizoxime) exhibited the least inhibition among ATOICs tested. The Ki values of typical ATOICs except ceftizoxime were 10-8-10-9M for enzymes from Citrobacter freundii, and Enterobacter sp. and 10-6-10-7M for those from Escherichia coli, Serratia marcescens and Pseudomonas aeruginosa.

A fuel assembly analysis code, VMONT, in which a multigroup neutron transport calculation is combined with a burnup calculation, has been developed for comprehensive design work use. The neutron transport calculation is performed with a vectorized Monte Carlo method that can realize speeds >10 times faster than those of a scalar Monte Carlo method. The validity of the VMONT code is shown through test calculations against continuous energy Monte Carlo calculations and the PROTEUS tight lattice experiment.

The properties of the abnormal ribonucleoprotein particles produced by Escherichia coli Q-13 starved for glucose were studied. Smaller species of these partially deproteinized particles separable to six distinct sizes contained partially degraded ribonucleic acids. The mode of ribosome degradation under this condition is discussed in terms of differential appearance of these intermediate particles.

The differences in ribosomal degradation and the fate of degradation products between Escherichia coli wild-type (B) and a ribonuclease less mutant (Q-13) during phosphate starvation were compared. The degradation rate of 32P-labeled ribosomes was found to be of the same order at the early stage but to differ at the later stage of deficiency between Escherichia coli B strain and Q-13 strain. The degradation in Q-13 nearly stopped after 6-h starvation, while it continued for more than 10 h in B strain, resulting in more than 80% degradation of 32P-prelabeled ribosomes. In the acid-soluble 32P pool of Q-13 strain, there was an increase in the nucleoside monophosphates but no increase and a continuous decrease in nucleoside di-and triphosphates, respectively. Q-13 contained no nucleoside 2′,3′-cyclic phosphate or nucleoside 3′-phosphate and little oligonucleotide, all of which had been detected in B strain during this stage. From these facts it was suggested that ribosomal RNA degradation in Escherichia coli Q-13 is mainly caused by ribonuclease II in vivo.

1. 1. Escherichia coli ribosomal RNA degradation during the phosphorus-deficient stage 1,2 was investigated by analysis of its degradation products. 2. 2. After exhaustion of the phosphorus in the medium, 32 P in the 50 % ethanolsoluble fraction of the bacterial cell increased greatly in parallel with the degradation of ribosomal RNA, while trichloroacetic acid-soluble 32 P did not. 3. 3. Soon after phosphorus exhaustion, most of the ethanol-soluble 32 P consisted of characteristic oligonucleotides. Later, inorganic phosphate increased gradually parallel with a decrease in oligonucleotides in ethanol extracts. 4. 4. The differences in the base ratios, the terminal structures and other properties of these oligonucleotides suggest that the breakdown of ribosomal RNA was caused mainly by ribosomal latent ribonuclease (EC 2.7.7.17) 3 . These oligonucleotides, in their turn, were found to be finally converted to inorganic phosphate and nucleosides by the cooperation of alkaline phosphomonoesterase (EC 3.1.3.1) 2,4 and cyclic phosphodiesterase 5,6 .

A closer investigation was carried out into the acid-soluble nucleotides of Escherichia coli B during the phosphorus-deficient stage in order to clarify the mechanism of reutilization of the degradation products of ribosomal RNA by the ribonuclease system. Inorganic phosphate and nucleosides were found to be final products arising from the hydrolysis of Nuc-2′,3′-P to Nuc-3′-P, and the conversion of these to precursors of DNA or mRNA via Nuc-5′-P is described. 1. 1. After exhaustion of the phosphorus in the medium, the amounts of polyphosphorylated nucleotides, P1 and NAD were first shown to decrease greatly and then all, except NAD, increased gradually in proportion to the degradation of rRNA. 2. 2. In the early stages of phosphorus deficiency, the amount of monophosphorylated nucleotides was very high but this decreased with time. The peaks corresponding to the four authentic Nuc-5′-P compounds on Dowex-1 chromatograms at this stage were found to represent mainly Nuc-5′-P and Nuc-3′-P which seemed to be intermediates in the degradation of rRNA. The amounts of Nuc-5′-P were initially low but increased gradually with time. 3. 3. On the whole, the ratio of deoxyribonucleotide to ribonucleotide in acidsoluble extracts of phosphorus-deficient cells is higher than that of normal cells, especially in the di- and triphosphorylated nucleotide regions. However, the absolute amount of deoxyribonucleotides present was not significantly different from normal, indicating that there was only a relative decrease in these ribonucleotides. 4. 4. Nucleosides in trichloroacetic acid extracts from phosphorus-deficient cells increased and these were composed mainly of uridine and inosine.