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Preventing coronavirus disease (COVID-19) outbreaks and the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from urban areas to less-populated remote islands, many of which may have weak medical systems, is an important issue. Here, we evaluated the usefulness of pre-boarding, saliva-based polymerase chain reaction (PCR) screening tests to prevent the spread of SARS-CoV-2 from Tokyo to the remote island of Chichijima. The infection rate on the island during the study period from September 1, 2020 to March 21, 2021 was 0.015% (2/13,446). Of the 8,910 individuals tested before ship boarding, seven tested positive for COVID-19 (PCR tests of saliva samples). One was confirmed positive by subsequent confirmatory nasopharyngeal swab testing. Based on the testing results, positive cases were denied entry onto the ship to prevent the spread of COVID-19 from Tokyo to Chichijima. This study demonstrated that implementing pre-boarding PCR screening tests is a useful strategy that can be applied to other remote islands with vulnerable medical systems.

High-flow nasal cannula (HFNC) can be effective in treating type 1 respiratory failure by reducing the severity of coronavirus disease 2019 (COVID-19). The purpose of this study was to assess the reduction of disease severity and safety of HFNC treatment in patients with severe COVID-19. We retrospectively observed 513 consecutive patients with COVID-19 admitted to our hospital from January 2020 to January 2021. We included patients with severe COVID-19 who received HFNC for their deteriorating respiratory status. HFNC success was defined as improvement in respiratory status after HFNC and transfer to conventional oxygen therapy, while HFNC failure was defined as transfer to non‐invasive positive pressure ventilation or ventilator, or death after HFNC. Predictive factors associated with failure to prevent severe disease were identified. Thirty-eight patients received HFNC. Twenty-five (65.8%) patients were classified in the HFNC success group. In the univariate analysis, age, history of chronic kidney disease (CKD), non-respiratory sequential organ failure assessment (SOFA) ≥ 1, oxygen saturation to fraction of inspired oxygen ratio (SpO(2)/FiO(2)) before HFNC ≤ 169.2, were significant predictors of HFNC failure. Multivariate analysis revealed that SpO(2)/FiO(2) value before HFNC ≤ 169.2 was an independent predictor of HFNC failure. No apparent nosocomial infection occurred during the study period. Appropriate use of HFNC for acute respiratory failure caused by COVID-19 can reduce the severity of severe disease without causing nosocomial infection. Age, history of CKD, non-respiratory SOFA before HFNC ≤ 1, and SpO(2)/FiO(2) before HFNC ≤ 169.2 were associated with HFNC failure.

The aim of this study was to determine the efficacy and safety of ciclesonide in the treatment of novel coronavirus disease 2019 (COVID-19) as gauged by pneumonia progression. This multi-center, open-label randomized trial was conducted with patients recruited from 22 hospitals across Japan. Participants were patients admitted with mild or asymptomatic COVID-19 without signs of pneumonia on chest X-rays. Asymptomatic participants were diagnosed after identification through contact tracing. Trial participants were randomized to either the ciclesonide or control arm. Participants in the treatment arm were administered 400 µg of ciclesonide three times a day over seven consecutive days. The primary endpoint was exacerbated pneumonia within seven days. Secondary outcomes were changes in clinical findings, laboratory findings, and changes over time in the amount of the viral genome. In the treatment group, 16 patients (39.0%) were classified as having exacerbated pneumonia compared to 9 (18.8%) in the control group. The risk ratio (RR) was 2.08 (95% confidence interval (CI): 1.15-3.75), indicating a worsening of pneumonia in the ciclesonide group. Significant differences were noted in participants with a fever on admission (RR: 2.62, 90% CI: 1.17-5.85, 95% CI: 1.00-6.82) and individuals 60 years of age or older (RR: 8.80, 90% CI: 1.76-44.06, 95% CI: 1.29-59.99). The current results indicated that ciclesonide exacerbates signs of pneumonia on images in individuals with mild or asymptomatic symptoms of COVID-19 without worsening clinical symptoms.

We herein report a 67-year-old kidney transplant patient who died of COVID-19. He was treated with hydroxychloroquine and azithromycin and received mechanical ventilation that temporarily improved his respiratory status. Despite our efforts, however, he later developed respiratory failure and died 43 days after the disease onset. The autopsy revealed prominent organization of alveoli and alveolar ducts, with a massive accumulation of macrophages in the lungs. A few severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen-positive cells were detected in the lung, suggesting delayed virus clearance owing to his long-term immunosuppressed state, leading to constant lung damage and ultimately respiratory failure.

We investigate interrelationships between gut microbes, metabolites, and cytokines that characterize COVID-19 and its complications, and we validate the results with follow-up, a Japanese Disease, Drug, Diet, Daily Life microbiome cohort, and non-Japanese data sets.We performed shotgun metagenomic sequencing and metabolomics on stools and cytokine measurements on plasma from 112 hospitalized patients with SARS-CoV-2 infection and 112 non-COVID-19 control individuals matched by important confounders.Multiple correlations were found between COVID-19-related microbes (eg, oral microbes and short-chain fatty acid producers) and gut metabolites (eg, branched-chain and aromatic amino acids, short-chain fatty acids, carbohydrates, neurotransmitters, and vitamin B6). Both were also linked to inflammatory cytokine dynamics (eg, interferon γ, interferon λ3, interleukin 6, CXCL-9, and CXCL-10). Such interrelationships were detected highly in severe disease and pneumonia; moderately in the high D-dimer level, kidney dysfunction, and liver dysfunction groups; but rarely in the diarrhea group. We confirmed concordances of altered metabolites (eg, branched-chain amino acids, spermidine, putrescine, and vitamin B6) in COVID-19 with their corresponding microbial functional genes. Results in microbial and metabolomic alterations with severe disease from the cross-sectional data set were partly concordant with those from the follow-up data set. Microbial signatures for COVID-19 were distinct from diabetes, inflammatory bowel disease, and proton-pump inhibitors but overlapping for rheumatoid arthritis. Random forest classifier models using microbiomes can highly predict COVID-19 and severe disease. The microbial signatures for COVID-19 showed moderate concordance between Hong Kong and Japan.Multiomics analysis revealed multiple gut microbe-metabolite-cytokine interrelationships in COVID-19 and COVID-19related complications but few in gastrointestinal complications, suggesting microbiota-mediated immune responses distinct between the organ sites. Our results underscore the existence of a gut-lung axis in COVID-19.

BACKGROUND polymyxin B-immobilized fiber column (PMX, Toraymyxin column) was approved for the relief of SIRS (systemic inflammatory response syndrome) caused by bacterial infection or endotoxemia. PMX reduces lung damage by removing leukocytes and cytokines in addition to endotoxin removal, in the setting of idiopathic pulmonary fibrosis. Acute exacerbation of interstitial pneumonia pathologically presents with diffuse alveolar damage (DAD). PMX direct hemoperfusion (PMX-DHP) demonstrated efficacy, improving oxygenation. SARS-CoV-2 virus causes COVID-19 pneumonia that emerged in December 2019. The condition may become severe about 1 week after onset, and respiratory failure rapidly develops, requiring intensive care management. A characteristic of COVID-19-related severe pneumonia is ground-glass opacities rapidly progressing in both lungs, which subsequently turn into infiltrative shadows. This condition could be classified as DAD. As for the congealing fibrinogenolysis system, D-dimer, fibrin/fibrinogen degradation product quantity and prolonged prothrombin time were significant factors in non-surviving COVID-19 cases, associated with aggravated pneumonia. Clinical trials are being conducted but, with the exception of remdesivir and dexamethasone, no treatments have yet been approved. COVID-19 aggravates with the deterioration of oxygen saturation, decrease in lymphocytes and the occurrence of an abnormal congealing fibrinogenolysis system, leading to diffuse lung damage. Once the condition transitions from moderate to severe, it is most necessary to prevent further exacerbation by providing treatment what will suppress the above symptoms as soon as possible. OBJECTIVE to acquire treatment options to prevent the transition from acute exacerbation of interstitial pneumonia to DAD. The mechanism of action envisioned for PMX-DHP is to reduce congealing fibrinogenolysis system abnormalities and increase oxygenation by removing activated leucocytes and cytokines, which are risk factors for the aggravation of COVID-19-related pneumonia. METHODS we will conduct a multicenter prospective intervention single-group study to evaluate the efficacy and safety of direct hemoperfusion using PMX-DHP for COVID-19 patients. Efficacy will be evaluated by the primary endpoint, which is the rate of Ordinal Scale for Clinical Improvement after PMX-DHP of at least 1 point from a status of 4.5.6 on Day 15. The effect of PMX-DHP will be estimated by setting a control group with background factors from non-PMX-DHP patients enrolled in the COVID-19 registry. This study will be carried out as a single-group open-label study and will be compared with a historical control. The historical control will be selected from the COVID-19 registry according to age, gender, and severity of pneumonia. RESULTS this study will help determine PMX-DHP treatment options in the medical setting by quickly collecting and publishing information on patient background and on the efficacy and safety of treatment by PMX-DHP. CONCLUSIONS from a clinical perspective, PMX-DHP is expected to become a first-line therapy to address unmet medical needs and prevent the exacerbation from moderate to severe ARDS in COVID-19 cases.

Background There is limited understanding of the characteristics of patients with coronavirus disease 2019 (COVID-19) requiring hospitalization in Japan. Methods This study included 2638 cases enrolled from 227 healthcare facilities that participated in the COVID-19 Registry Japan (COVIREGI-JP). The inclusion criteria for enrollment of a case in COVIREGI-JP are both (1) a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test and (2) inpatient treatment at a healthcare facility. Results The median age of hospitalized patients with COVID-19 was 56 years (interquartile range [IQR], 40–71 years). More than half of cases were male (58.9%, 1542/2619). Nearly 60% of the cases had close contact to confirmed or suspected cases of COVID-19. The median duration of symptoms before admission was 7 days (IQR, 4–10 days). The most common comorbidities were hypertension (15%, 396/2638) and diabetes without complications (14.2%, 374/2638). The number of nonsevere cases (68.2%, n = 1798) was twice the number of severe cases (31.8%, n = 840) at admission. The respiratory support during hospitalization includes those who received no oxygen support (61.6%, 1623/2636) followed by those who received supplemental oxygen (29.9%, 788/2636) and invasive mechanical ventilation/extracorporeal membrane oxygenation (8.5%, 225/2636). Overall, 66.9% (1762/2634) of patients were discharged home, while 7.5% (197/2634) died. Conclusions We identified the clinical epidemiological features of COVID-19 in hospitalized patients in Japan. When compared with existing inpatient studies in other countries, these results demonstrated fewer comorbidities and a trend towards lower mortality.

Immune checkpoint inhibitors (ICIs) are reportedly effective against many kinds of neoplasm, but may be responsible for several kinds of immune‐related adverse events (irAEs). Among these irAEs, the incidence of myelosuppression due to ICIs is relatively low. Corticosteroids are needed to control most cases of myelosuppression. Here, we report an 88‐year‐old woman with squamous cell lung cancer who was administered pembrolizumab. After five cycles of pembrolizumab, she developed severe pancytopenia. The pancytopenia improved under observation without steroid administration after cessation of pembrolizumab. During recovery from this irAE, the patient also maintained long‐term antitumor efficacy. Key points Significant findings of the study There are several kinds of immune‐related adverse events. We encountered a case of pembrolizumab‐induced pancytopenia with squamous cell lung cancer. What this study adds Corticosteroids are needed to control most cases of myelosuppression induced by ICIs, but pancytopenia induced by pembrolizumab in our case improved without steroids., An 88‐year‐old woman with squamous cell lung cancer was administered pembrolizumab. After 5 cycles of pembrolizumab, she developed severe pancytopenia. Pancytopenia improved under observation without steroid administration after cessation of pembrolizumab. During recovery from this irAE, the patient also maintained long‐term anti‐tumor efficacy.

Background The current gold standard in coronavirus disease (COVID-19) diagnostics is the real-time reverse transcription–polymerase chain reaction (RT-PCR) assay for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in nasopharyngeal swab (NPS) samples. Alternatively, nasal swab (NS) or saliva swab (SS) specimens are used, although available data on test accuracy are limited. We examined the diagnostic accuracy of NPS/NS/SS samples for this purpose. Methods Ten patients were included after being tested positive for SARS-CoV-2 RT-PCR in NPS samples according to the National Institute of Infectious Disease guidelines. In comparison with this conventional diagnostic method, NPS/NS/SS samples were tested using the cobas 6800 systems RT-PCR device. To investigate the usefulness of the cobas method and the difference among sample types, the agreement and sensitivity were calculated. Five to six samples were collected over a total period of 5–6 d from each patient. Results Fifty-seven sets of NPS/NS/SS samples were collected, of which 40 tested positive for COVID-19 by the conventional method. Overall, the concordance rates using the conventional method were 86.0%/70.2%/54.4% for NPS/NS/SS samples (cobas); however, for samples collected up to and including on Day 9 after disease onset (22 negative and one positive specimens), the corresponding rates were 95.7%/87.0%/65.2%. The overall sensitivity estimates were 100.0%/67.5%/37.5% for NPS/NS/SS samples (cobas). For samples up to 9 d after onset, the corresponding values were 100.0%/86.4%/63.6%. Conclusions NS samples are more reliable than SS samples and can be an alternative to NPS samples. They can be a useful diagnostic method in the future.

The quantitative range and reproducibility of current serological tests for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are not optimized. Herein, we developed a diagnostic test that detects SARS-CoV-2 IgG and IgM with high quantitativeness and reproducibility and low interference. The system was based on the high-sensitivity chemiluminescence enzyme immunoassay (HISCL) platform and detects IgG and IgM specific to SARS-CoV-2 spike and nucleocapsid proteins. Quantification accuracy and reproducibility were evaluated using serially diluted samples from 60 SARS-CoV-2-infected patients. Assay performance was evaluated using serum samples from the SARS-CoV-2-infected patients and 500 SARS-CoV-2-negative serum samples collected before the emergence of SARS-CoV-2. The system showed high quantification accuracy (range, 102), high reproducibility (within 5%), and no cross-reaction between SARS1- and MERS-S proteins. Detection accuracy was 98.3% and 93.3% for IgG and IgM against spike proteins and 100% and 71.7% for IgG and IgM against nucleocapsid proteins, respectively. Mean antibody levels were > 10 times that in negative samples upon admission and > 100 times that at convalescent periods. Clinical severity upon admission was not correlated with IgG or IgM levels. This highly quantitative, reproducible assay system with high clinical performance may help analyze temporal serological/immunological profiles of SARS-CoV-2 infection and SARS-CoV-2 vaccine effectiveness.

Angiotensin converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2), two receptors on the cell membrane of bronchial epithelial cells, are indispensable for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. ACE2 receptor is increased among aged, males, and smokers. As smoking upsurges ACE2 expression, chronic obstructive pulmonary disease (COPD) patients are prone to SARS-CoV-2 infection, and are at a higher risk for severe forms of COVID-19 (coronavirus disease 2019) once infected. The expression of ACE2 and TMPRSS2 in asthma patients is identical (or less common) to that of healthy participants. ACE2 especially, tends to be low in patients with strong atopic factors and in those with poor asthma control. Therefore, it could be speculated that asthma patients are not susceptible to COVID-19. Epidemiologically, asthma patients are less likely to suffer from COVID-19, and the number of hospitalized patients due to exacerbation of asthma in Japan is also clearly reduced during the COVID-19 pandemic; therefore, they are not aggravating factors for COVID-19. Related academic societies in Japan and abroad still lack clear evidence regarding asthma treatment during the COVID-19 pandemic, and recommend that regular treatment including biologics for severe patients be continued.

BACKGROUND Currently, there are no specific effective treatments for SARS-CoV-2 infection; however, various COVID-19 treatment options are under investigation. It is vital to continue investigating the landscape of SARS-CoV-2–induced pneumonia and therapeutic interventions. OBJECTIVE This paper presents the protocol for a randomized controlled trial that aims to compare the pneumonia exacerbation rate between ciclesonide (ALVESCO; Teijin Pharma Limited) administration and symptomatic treatment in patients with COVID-19 and to determine the efficacy of ciclesonide. The secondary objectives are to investigate the safety of ciclesonide administration, changes in clinical and laboratory findings, and the number of viral genome copies of SARS-CoV-2 over time between the 2 groups. METHODS In this investigator-initiated, exploratory, prospective, multicenter, parallel-group, open-label, randomized controlled trial, a total of 90 patients diagnosed with COVID-19 will be recruited from 21 hospitals in Japan based on specific inclusion and exclusion criteria. Participants will be randomized either to the ciclesonide group, which will receive a 400-µg dose of ciclesonide 3 times per day over a 7-day period, or to the symptomatic treatment group. Both groups will receive antitussives and antipyretics as required. Data collection for various parameters will be conducted on days 1, 2, 4, 8, 22, and 29 to record baseline assessments and the findings over an extended period. Computed tomography images taken prior to drug administration and 1 week following treatment will be compared, and efficacy will be confirmed by checking for pneumonia exacerbation. Primary endpoint analysis will be performed using the Fisher exact test to determine statistically significant differences in the pneumonia exacerbation rate between the ciclesonide and symptomatic treatment groups. RESULTS The first trial participant was enrolled on April 3, 2020. Recruitment is expected to be completed on September 30, 2020, while follow-up assessments of all participants are expected to be completed by October 31, 2020. The study results will be published in a peer-reviewed scientific journal. CONCLUSIONS The RACCO (Randomized Ciclesonid COVID-19) study will provide definitive comparative effectiveness data and important clinical outcomes data between the ciclesonide and symptomatic treatment groups. If the hypotheses that pneumonia exacerbation rate reduction is more significant in the ciclesonide treatment group than in the symptomatic treatment group and that ciclesonide is safe for use are valid, ciclesonide will serve as an important therapeutic option for patients with COVID-19. CLINICALTRIAL Japan Registry of Clinical Trials jRCTs031190269; https://jrct.niph.go.jp/en-latest-detail/jRCTs031190269 INTERNATIONAL REGISTERED REPORT DERR1-10.2196/23830

Supplemental Digital Content is available in the text., Subjects: Early detection of coronavirus disease 2019 in patients likely to develop severe manifestations enables appropriate interventions, including rapid ICU admission. This study was conducted to determine whether noninvasive urine biomarkers can predict the clinical severity of coronavirus disease 2019. Interventions: Not applicable. Measurements and Main Results: This is single-center study, national center hospital designated for infectious disease. Fifty-eight patients who tested positive for severe acute respiratory syndrome coronavirus 2 in respiratory specimens through real-time reverse transcription-polymerase chain reaction were retrospectively studied. Urinary β2-microglobulin, liver-type fatty acid-binding protein were serially measured. Serum interferon-γ and monocyte chemotactic protein-1 were also evaluated. The 58 patients were assigned into three groups. Patients requiring intensive care were assigned to the severe group (n = 12). Patients treated with oxygen were assigned to the moderate group (n = 13). Other patients were assigned to the mild group (n = 33). Urine tests revealed that low β2-microglobulin and liver-type fatty acid-binding protein levels were associated with mild disease, whereas high levels were associated with severe disease. In severe cases, liver-type fatty acid-binding protein tended to be persistently high. The resulting cutoff values were β2-microglobulin; severe versus moderate + mild: 2,457 μg/dL (specificity 76.9% and sensitivity 90.0%, area under the receiver operating characteristic curve 85.9%), liver-type fatty acid-binding protein; severe versus moderate + mild: 22.0 μg/gCre (specificity 84.6% and sensitivity 90%, area under the receiver operating characteristic curve 91.8%). Urinary β2-microglobulin and serum interferon-γ/monocyte chemotactic protein-1 showed a similar trend. Conclusions: Evaluating urinary biomarkers such as β2-microglobulin and liver-type fatty acid-binding protein may allow determination of coronavirus disease 2019 patients with active cytokines and recognition of patients likely to become critically ill and requiring careful observation and early intervention.

To the Editor,A recent report in this journal described the severe nature and potentially fatal outcome of coronavirus disease 2019 (COVID-19) [1]. We here report a severe familial cluster case in ...

Background Currently, there are no specific effective treatments for SARS-CoV-2 infection; however, various COVID-19 treatment options are under investigation. It is vital to continue investigating the landscape of SARS-CoV-2–induced pneumonia and therapeutic interventions. Objective This paper presents the protocol for a randomized controlled trial that aims to compare the pneumonia exacerbation rate between ciclesonide (ALVESCO; Teijin Pharma Limited) administration and symptomatic treatment in patients with COVID-19 and to determine the efficacy of ciclesonide. The secondary objectives are to investigate the safety of ciclesonide administration, changes in clinical and laboratory findings, and the number of viral genome copies of SARS-CoV-2 over time between the 2 groups. Methods In this investigator-initiated, exploratory, prospective, multicenter, parallel-group, open-label, randomized controlled trial, a total of 90 patients diagnosed with COVID-19 will be recruited from 21 hospitals in Japan based on specific inclusion and exclusion criteria. Participants will be randomized either to the ciclesonide group, which will receive a 400-µg dose of ciclesonide 3 times per day over a 7-day period, or to the symptomatic treatment group. Both groups will receive antitussives and antipyretics as required. Data collection for various parameters will be conducted on days 1, 2, 4, 8, 22, and 29 to record baseline assessments and the findings over an extended period. Computed tomography images taken prior to drug administration and 1 week following treatment will be compared, and efficacy will be confirmed by checking for pneumonia exacerbation. Primary endpoint analysis will be performed using the Fisher exact test to determine statistically significant differences in the pneumonia exacerbation rate between the ciclesonide and symptomatic treatment groups. Results The first trial participant was enrolled on April 3, 2020. Recruitment is expected to be completed on September 30, 2020, while follow-up assessments of all participants are expected to be completed by October 31, 2020. The study results will be published in a peer-reviewed scientific journal. Conclusions The RACCO (Randomized Ciclesonid COVID-19) study will provide definitive comparative effectiveness data and important clinical outcomes data between the ciclesonide and symptomatic treatment groups. If the hypotheses that pneumonia exacerbation rate reduction is more significant in the ciclesonide treatment group than in the symptomatic treatment group and that ciclesonide is safe for use are valid, ciclesonide will serve as an important therapeutic option for patients with COVID-19. Trial Registration Japan Registry of Clinical Trials jRCTs031190269; https://jrct.niph.go.jp/en-latest-detail/jRCTs031190269 International Registered Report Identifier (IRRID) DERR1-10.2196/23830

Activities of Calvin-Benson cycle enzymes were found in protoplasts of guard cells from Vicia faba L. The activities of NADP-glyceraldehyde-3-phosphate dehydrogenase (NADP-GAPD) and ribulose-1,5-bisphosphate carboxylase (RuBPC) were 2670 and 52 micromoles per milligrams chlorophyll per hour, respectively. Activities of NADP-GAPD and RuBPC in guard cells were increased by red light illumination, and the light activations were inhibited completely by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosystem II. Enzymes related to the Calvin-Benson cycle such as 3-phosphoglycerate kinase (PGAK), triose phosphate (TP) isomerase, and fructose-1,6-bisphosphatase (FBPase) were shown to be present in guard-cell chloroplasts. From these results, we conclude that the photosynthetic carbon reduction pathway is present in guard-cell chloroplasts of Vicia faba. We compared these enzyme activities in guard cells with those in mesophyll cells. The activities of NADP-GAPD and PGAK were more than several-fold higher and that of TP isomerase was much higher in guard-cell chloroplasts than in mesophyll chloroplasts. In contrast, activities of RuBPC and FBPase were estimated to be roughly half of those in mesophyll chloroplasts. High activities of PGAK, NAD-GAPD, and TP isomerase were found in fractions enriched in cytosol of guard cells. Illumination of guard-cell protoplasts with red light increased the cellular ATP/ADP ratio from 5 to 14. These results support the interpretation that guard cells utilize a shuttle system (e.g. phosphoglycerate [PGA]/dihydroxyacetone phosphate [DHAP] shuttle) for an indirect transfer of ATP and reducing equivalents from chloroplasts to the cytosol.

5'-IMP and related 5'-nucleotides are potent flavor substances contained in some foods. Sodium salts of 5'-IMF and other 5'-nucleotides were dissolved in distilled water or buffered solution and sealed in glass ampoules under atmosphere. The samples were irradiated with a 5, 000 curie cobalt-60 source at the dose rates of 2.3×103-3.6×105 r/hr at room temperature.The residual levels of 5'-IMP irradiated at 1.0 Mrad were 61 and 86% in distilled water and in buffer of pH 7 (Fig. 2), respectively. The decimal reduction dose at pH 7 was 17.2 Mrad. 5'-IMP was found to be more labile at pH 3 and 5 rather than at pH 7 and 9 (Fig. 3). Irradiation of 5'-IMP led to the splitting of the bond between nucleic base and ribose phosphate, resulting in the increase of hypoxanthine (Table 5 and 6).There is a significant difference between the mode of decomposition affected by heating and by γ-irradiation.Purine nucleotides are more stable than pyrimidine nucleotides against γ-irradiation (Table 3 and 4), but the formers are more labile than the latters against heating. Existence of sugar is protective against the destruction by γ-ray (Fig. 5) but is promotive of that by heat.