[The value of Alcian blue periodic acid Schiff staining and Ki-67 expression in diagnosing gastric reactive epithelial hyperplasia and dysplasia].

Objective: To investigate the clinicopathological characteristics of reactive epithelial hyperplasia and dysplasia in the stomach, as well as the clinical value of mucin special staining and proliferating cell nuclear antigen (Ki-67) in distinguishing the two gastric lesions. Methods: The clinical pathological data of 63 patients with gastric reactive epithelial hyperplasia, 54 patients with low-grade dysplasia, and 63 patients with high-grade dysplasia diagnosed from May 2018 to May 2021 in Beijing Chaoyang Hospital, Capital Medical University, Beijing, China were analyzed. Alcian blue periodic acid Schiff (AB-PAS) and Ki-67 staining were performed to examine the mucin staining pattern, number of Ki-67 positive cells, Ki-67 staining patterns in the three groups of lesions, and histopathologic characteristics. Results: The positive rates of AB-PAS in the reactive epithelial hyperplasia and gastric dysplasia groups were 87.3%(55/63) and 10.3%(12/117), respectively. The expression of AB-PAS in the reactive epithelial hyperplasia was gradually increased from the base to the surface of the epithelium. In low-grade dysplasia and high-grade dysplasia, there was no mucin present in the dysplasia epithelium. The difference between the two groups was statistically significant (P<0.01). The positive rate of Ki-67 in the epithelial reactive hyperplasia (>10%) was 81.0% (51/63), and the positive cells were mainly located in the neck and middle parts of the mucosal glands (58/63, 92.1%). In the low-grade dysplasia group, the positive rate of Ki-67 (>10%) was 90.7%(49/54); the positive cells were mainly located in the upper mucosa (33/54, 61.1%), showing a banded distribution pattern; in the high-grade dysplasia group, the positive rate (>10%) was 95.2%(60/63), and the positive cells were mainly located in the whole mucosa (49/63, 77.8%), showing a diffuse/diffuse scattered distribution pattern. The three groups had statistically different rates and distribution patterns of Ki-67 expression (P<0.01). Conclusion: The gastric epithelial reactive hyperplasia and dysplasia can be differentiated using clinicopathological features, AB-PAS staining and Ki-67 expression pattern.

[Boss mass index and mortality from cardiovascular disease in China: a prospective study in rural men].

Objective: To assess the relationship between body mass index (BMI) and death risk of cardiovascular disease (CVD) in rural male population. Methods: 22 282 men aged 40 years older in Tanghe county and Fenghuang county from the cohort of the "Prospective Study on Adult Behavior and Health Risk Factors in China" were selected as subjects of this study. Cox regression model was used to calculate the hazard ratios (HRs) of the death of CVD during the follow-up period with different BMI groups at baseline. Results: The average follow-up period in the two counties was (19.1±8.7) years and 10 828 (48.6%) people died during the follow-up period. 4 504 deaths were attributed to CVD. Among the deaths of CVD, 1 279 cases died of ischemic heart disease (IHD), ischemic stroke (IS) died in 1 201, cases died of died of 1 317 hemorrhagic stroke (HS), other 707 cases. Compared to population with BMI<18 kg/m(2), Cox regression model (adjusting factors of region, age, nationality, education level, occupation, smoking, drinking, blood pressure, blood pressure, etc.) showed that people with BMI between 20-22 kg/m(2) had the lowest risk of CVD death (HR=0.95, 95%CI: 0.83-1.09). But the difference was not statistically significant among each BMI group (P>0.05). The risk of IHD death was the lowest in the population with BMI between 20-22 kg/m(2) (P<0.05) (HR=0.64, 95%CI: 0.52-0.80). There was no statistically significant difference between the risk of IHD death in the population with BMI≥24 kg/m(2) and that in the population with BMI<18 kg/m(2) (P>0.05). There was no statistically significant difference between the risk of IS death and BMI (P>0.05). The death risk of HS in the population with BMI between 18-24 kg/m(2) was higher than that in the population with BMI<18 kg/m(2) (P<0.05). The death risk of the population with BMI between 26-28 kg/m(2) was the highest (HR=1.88, 95%CI:1.18-2.99). Conclusions: The mortality risk of CVD and IHD was the lowest in lean or normal weight group, and HS was higher in overweight group. Maintaining a reasonable weight can reduce the risk of death in patients with CVD.

[Research on the relationship between environmental chemical pollutant exposure and epigenetics].

Environmental chemical pollutants are increasing, which brings various harms to human health. Epigenetics may be an important medium between exposure to environmental chemical contaminants and adverse health effects. Many environmental chemical pollutant exposures can regulate gene expression and promote disease occurrence and development through epigenetic mechanisms. This review outlines the mechanisms of epigenetics and the latest research advances in exposure and epigenetics of several environmental chemical substances (heavy metal arsenic, bisphenol A, dioctyl phthalate and benzene). To further understand and study the relationship between environmental chemical pollutant exposures and epigenetics in order to elucidate the mechanisms of disease occurrence and development.

ARHGAP15 regulates lung cancer cell proliferation and metastasis via the STAT3 pathway.

OBJECTIVE: Lung cancer, which is typically diagnosed at later stages, is a leading cause of cancer death among both males and females given its highly invasive and rapidly metastasizing nature. Rho GTPase activating protein 15 (ARHGAP15) is a member of the RhoGAP family and functions in multiple biological processes, such as cell proliferation and migration. However, the effect of ARHGAP15 in lung cancer and its underlying molecular mechanisms remain unclear. PATIENTS AND METHODS: In this study, immunohistochemistry and Real Time PCR were performed to detect ARHGAP15 expression in lung cancer tissues and cells. Proliferation, transwell, and Western blot assays were further performed to explore the role and underlying mechanism of ARHGAP15 in lung cancer. RESULTS: Reduced ARHGAP15 expression was observed in lung cancer tissues and cells. In vitro upregulation of ARHGAP15 in lung cancer cells strongly suppressed cell proliferation, migration, and invasion and was accompanied by reduced matrix metalloproteinase-2 (MMP2), MMP9, vascular endothelial growth factor (VEGF) expression, and the phosphorylation of the signal transducer and activator of transcription-3 (p-STAT3). In contrast, interleukin-6 (IL-6) had the opposite effect and the induction of IL-6 was counteracted by ARHGAP15 upregulation. In addition, the proliferation, migration, and cell invasion induced by ARHGAP15 silencing were potentially inhibited by the STAT3 inhibitor AG490 (100 µM), MMP2, MMP9, VEGF, and p-STAT3 levels decreased. CONCLUSIONS: These results suggest that ARGFAP15 suppressed the proliferation and metastasis of lung cancer cells, which may occur through the inhibition of MMP2, MMP9, and VEGF expression via the STAT3 pathway inactivation.

Characterization of the NLRC5 promoter in chicken: SNPs, regulatory elements and CpG islands.

NLRC5 plays an important role in the innate immunity and cellular immunity in many species, but the regulatory mechanism of NLRC5 expression in chickens remains unclear. In this study, a series of deletion fragments of the NLRC5 promoter region were constructed and dual-luciferase assay was performed. Then, we detected the SNP in the core region and its function. Important transcriptional regulatory elements were predicted and identified. Methylation of CpG islands was measured. The results revealed that the two core regions of -4372 to -3756 and -2925 to -2265 in the NLRC5 promoter were essential for NLRC5 mRNA expression in which a SNP (A/G), located at -2470, was found to have an effect on the transcriptional activity. Also, the STAT1 element in the second core region of the NLRC5 promoter was identified to bind with the STAT1 transcription factor, which was necessary for the transcriptional activity. In addition, many other elements in the NLRC5 promoter, including YY1 and CEBP, may contribute significantly to the expression activity of NLRC5. Moreover, two CpG islands were searched. Part of one was located in the first core region, which suggests that epigenetic modification may regulate the activity of the first promoter region, and the other was mostly in an unmethylated state. Collectively, these results suggest the complex regulation of NLRC5 expression includes SNPs, transcription factors and methylation.

[Relationship between N-nitrosodimethylamine and risk of digestive tract cancers: a Meta analysis based on cohort studies].

OBJECTIVE: To analyze the relationship between N-nitrosodimethylamine(NDMA)and the risk of digestive tract cancers. METHODS: The papers about the relationship between NDMA and the risk of digestive tract cancers published from 1980 to 2012 were retrieved following databases: Chinese BioMedical Literature Database(CBM), the Chinese Journal Full-text Database(CNKI), Wanfang Database, PubMed and EBSCO. The fix and random effect model was used and statistical analyses were conducted by using RevMan 5.1 software. RESULTS: Thirteen papers were found, in which 7 about digestive tract cancers were used in this Meta analysis. The NDMA had significant positive effect on the incidence of digestive tract cancers(RR=1.12, 95% CI: 1.03-1.21). The relationship between NDMA and esophageal cancer was not significant(RR=1.18, 95%CI: 0.98-1.41)but NDMA could increase the risk of gastric cancer(RR=1.08, 95% CI: 1.00-1.18). For the subtypes of esophageal and gastric cancer, NDMA had positive relationship with esophageal squamous cell carcinoma(RR=1.72, 95% CI: 1.01-2.96), but had no significant relationship with esophageal adenocarcinoma, cardiac carcinoma and gastric adenocarcinoma. CONCLUSION: The population-based cohort studies have showed that the NDMA could significantly increase the risk of digestive tract cancers, but the effects differed with subtypes of esophageal and gastric cancer. However, it is necessary to collect more evidence due to the limited studies and obvious differences in the study design, sampling and exposure measurement of these cohort studies.

Gene expression changes in chicken NLRC5 signal pathway associated with in vitro avian leukosis virus subgroup J infection.

Nucleotide-binding oligomerization domain-like receptors (NLRs) play a key role in the innate immune response as pattern-recognition receptors. However, the role of NLRC5, which is a member of the NLR family, in NF-κB activation and MHC-I expression remains debatable. Infection with the J group avian leukosis virus (ALV-J) can result in immunosuppression and a subsequent increase in susceptibility to secondary infection. This results in huge economic losses to the poultry industry worldwide. Using quantitative real-time polymerase chain reaction (qRT-PCR), we investigated the mRNA expression levels of NLRC5 signal pathway-related genes in secondary chicken embryo fibroblasts 7 days after infection with ALV-J. The results indicated that, compared with the control groups, the expression levels of TLR7, MHC-I, and IL-18 increased significantly in the infected groups at 7 days post-infection (d.p.i.). The expression levels of NLRC5 and IL-6 were conspicuously downregulated at 7 d.p.i., but the expression levels of NF-κB, STAT1, and STAT3 were not significantly altered. These results suggest that NLRC5 and some genes involved in the NLRC5 pathway play a key role in antiviral immunity, typically the response to ALV-J infection. Moreover, MHC-I expression levels vary between different cell types.

Potential impact of cardiac dose-volume on acute cardiac toxicity following concurrent trastuzumab and radiotherapy.

PURPOSE: To analyse the risk factors associated with acute cardiotoxicity in HER2-positive breast cancer patients receiving concurrent trastuzumab and radiotherapy. PATIENTS AND METHODS: Medical records of 45 breast cancer patients treated between 02/2009 and 02/2011 by concurrent trastuzumab and radiotherapy were collected. Radiation was delivered to the conserved breast or chest wall with or without regional nodes. Dose prescription was 50Gy in 25 fractions over five weeks with a tumor bed boost of 10Gy in 5 fractions in breast conservation. Acute cardiotoxicity (grade≥1) was defined using NCI-CTC v2.0. Doses to the heart and left ventricle were quantified. RESULTS: Median follow-up of left ventricular ejection fraction and clinical assessment from the completion of radiotherapy was 10 months (range: 3-27 months) and 25 months (range: 13-40 months), respectively. Ten (22.2%) and one (2.2%) of the 45 patients developed grade 1 and grade 2 cardiotoxicity, respectively. For 24 left-sided patients, the mean heart dose was significantly higher in those with cardiac events compared to those without (10.14 and 6.27Gy, respectively; P<0.05). A continuous increase of D17-D57 and V10-V15 of the heart and increase of D40-D80 and V5-V7 of the left ventricle were statistically significant in left-sided patients who developed cardiotoxicity compared with those who did not (P<0.05). No significant relationship of dosimetric parameters of cardiac structures and cardiac events was found in right-sided patients. CONCLUSIONS: Left-sided irradiation with increased low dose-volume and mean heart dose were associated with increased but reversible low-grade early cardiac toxicity after use of concurrent trastuzumab.

Structure and immune expression analysis of hemoglobin genes from the blood clam Tegillarca granosa.

Hemoglobin (Hb) is the major protein component of erythrocytes in animals with red blood, although it can serve additional functions beyond the transport of oxygen. The blood clam (Tegillarca granosa) is one of the few mollusks that has Hb, although the structure and function of molluskan Hbs remain unclear. We characterized two unique and highly compartmentalized blood clam hemoglobin genes, Tg-HbIIA and Tg-HbIIB, at the molecular level. The full-length cDNA of Tg-HbIIA was 731 bp with a 450-bp open reading frame encoding 150 amino acids; that of Tg-HbIIB was 698 bp, with a 456-bp open reading frame encoding 152 amino acids. Their intronic regions were amplified by PCR. The two genes showed the typical 2 intron/3 exon organization found in T. granosa. The 3-D structures of the three blood clam Tg-Hbs were predicted using the SWISS-MODEL Protein Modeling Server, and a phylogenetic analysis was conducted to investigate its evolution. As quantified by qRT-PCR, the expression levels of Tg-HbIIA and Tg-HbIIB were significantly upregulated upon challenge by Vibrio parahaemolyticus, lipopolysaccharides, and peptidoglycans. Three Hb isoforms, Tg-HbI, Tg-HbIIA, and Tg-HbIIB, were found. Specific structures and evolutionary features were found in these molluskan Hb genes. Challenge experiments indicated that Tg-Hbs are involved in immune defense responses against bacterial infection and bacterial pathogenic factors. As this is the first functional research on Hb genes in the blood clam, our findings provide new insight into the innate immune defense mechanisms of T. granosa.

Delineation of the cardiac substructures based on PET-CT and contrast-enhanced CT in patients with left breast cancer treated with postoperative radiotherapy.

The aim of this study is to evaluate the volume differences between contrast-enhanced CT-based left ventricle (LV) and PET-CT-based LV and assess the impact of dose on the substructure volume differences in patients with left breast cancer treated with adjuvant radiotherapy. From October 2008 to February 2009, 14 patients with post-operatively confirmed left breast cancer were enrolled in the current study. The patients were scanned using contrast-enhanced CT for simulation, and (18)F-FDG PET-CT was employed to display the structure of the left ventricle of each before radiotherapy (RT). The LV was delineated based on both contrast-enhanced CT and PET-CT. And other substructures, such as the left anterior descending coronary artery (LAD), were contoured in each patient, with the six-field simple intensity modulated radiotherapy (sIMRT) technique created for all. The mean volumes of the left ventricle based on contrast-enhanced CT (LV-CT) and PET-CT (LV-PET) were found to be 107.296 cm(3) and 112.931 cm(3), respectively (p = 0.06). The volume of LV receiving ≥ 50% prescription dose was significantly correlated with the volume of the heart receiving the same dosage (γ = 0.869). There was less correlation between the volume of LAD and that of the heart under the same condition (γ = 0.22). As a conclusion, the left ventricle can be delineated effectively based on the image of PET-CT, the contrast-enhanced CT based LV can serve as an appropriate alternative. Moreover, the volume of LV receiving high dose in RT closely correlated with the volume of the heart using sIMRT technique, which may pave the way for further exploring radiation-induced cardiac injuries in patients with left breast cancer.

Enhanced critical pressure for buckling of carbon nanotubes due to an inserted linear carbon chain.

Recent findings of linear carbon-atom chains (C-chains) inside carbon nanotubes have stimulated considerable interest. In this work, molecular dynamics (MD) simulation and an elastic string-elastic shell model is adopted to study radial pressure-induced buckling of single-walled carbon nanotubes (SWCNT) filled with a C-chain. The continuum model predicts that the C-chain increases critical buckling pressure considerably (about 40%-160%) for SWCNTs of diameters ranging from 0.68 to 0.72 nm, in reasonable quantitative agreement with the prediction of MD simulation. In particular, the MD simulation confirms that the originally circular cross section of filled SWNTs becomes elliptical after buckling, as predicted by the continuum model.

Neointimal coverage of bare-metal and sirolimus-eluting stents evaluated with optical coherence tomography.

OBJECTIVE: To analyse the neointimal coverage of sirolimus-eluting stent (SES) and bare-metal stent (BMS) visualised in vivo by optical coherence tomography (OCT). METHODS: OCT images were obtained in 26 coronary vessels of 24 patients at 5-93 months after SES or BMS deployment. The short-term BMS group (BMS1) consisted of eight BMS in seven patients at 5-10 months of follow-up, the long-term BMS group (BMS2) consisted of six BMS in six patients at 23-93 months of follow-up, and the SES group (SES) consisted of 13 SES in 10 patients at 6-12 months of follow-up. The strut apposition, strut coverage and mean maximal and minimal neointimal thicknesses (NIT) for both BMS groups and SES were compared. RESULTS: OCT images were acquired successfully. Significant differences between completely apposed and malapposed stent struts (p<0.0001) and between covered and uncovered stent struts (p<0.0001) were found among the three groups. The mean maximal and minimal NIT in the SES group were all significantly less than those of the BMS1 or BMS2 group, the minimal NIT in the BMS1 group was significantly less than that of the BMS2 but the mean maximal NIT was no significant difference between the BMS1 and BMS2 groups. In an open bifurcation artery, 19 struts visualised by OCT had no discernible coverage or were surrounded by either thrombus or a thick tissue layer. CONCLUSIONS: OCT imaging can clearly visualise stent apposition and neointimal coverage of stent struts. Incomplete strut apposition and lack of strut coverage occurred with a significantly higher frequency in SES than in BMS. These findings may explain the occurrence of late thrombosis in SES. Optical coherence tomography (OCT) is the optical analogue to ultrasound, measuring the back-reflection of infrared light instead of sound waves. The greatest advantage of OCT is its high resolution, which exceeds that of any currently available in vivo imaging technology. The resolution of catheter-based systems is in the range of 10-20 microm. Furthermore, resolutions as high as 4 microm have been achieved ex vivo with more sophisticated techniques that may be applicable to future catheter-based approaches. The main components of various atheromatous plaques can be identified in OCT images, and have been validated in a histology-controlled study. Several studies have demonstrated the feasibility of OCT imaging in patients undergoing percutaneous coronary intervention (PCI). The aim of the present study was to use OCT to analyse the neointimal coverage of sirolimus-eluting stents (SES), compared with that of bare-metal stents (BMS).

Association of haemoglobin level with morbidity and mortality of patients with locally advanced oesophageal carcinoma undergoing radiotherapy--a secondary analysis of three consecutive clinical phase III trials.

AIMS: To investigate the strength of association between anaemia and overall survival, locoregional control, and late radiation complications in patients with locally advanced oesophageal carcinoma undergoing radiotherapy with or without chemotherapy and hyperthermia. MATERIALS AND METHODS: Between March 1996 and December 2002, 303 patients with locally advanced squamous cell carcinoma of oesophagus enrolled in three consecutive prospective phase III trials conducted in our department were included in this study. These patients received one of the following four irradiation schedules: late course accelerated hyperfractionated (LCAF) radiotherapy alone, LCAF combined with concurrent chemotherapy, LCAF combined with hyperthermia, and continuous accelerated hyperfractionated (CAHF) radiotherapy according to each protocol. According to the haemoglobin levels measured before radiotherapy, patients were stratified to normal haemoglobin group (> or = 12.0 g/dl for men, or > or = 11.0 g/dl for women) or anaemic group (< 12.0 g/dl for men, or < 11.0 g/dl for women). Overall survival, locoregional control rate and late irradiation toxicity were estimated by Kaplan-Meier method. RESULTS: Of 303 eligible patients, 243 patients (80.2%) had normal haemoglobin level and 60 patients (19.8%) were anaemic. The 5-year overall survival was 39% in patients with normal haemoglobin level, whereas, 22%, with anaemia patients (P = 0.001). The 5-year locoregional control rate at 5 years was 68% in patients with normal haemoglobin, versus 62%, with anaemia patients (P = 0.050). The 5-year rate of radiation toxicity of grade 3 or greater was 29% in patients with normal haemoglobin level, but it was 8%, with anaemic patients (P = 0.033). From multivariate analyses, T stage, location of tumour and haemoglobin level were found to be independent predictors for survival. T stage, gender and haemoglobin level were independent predictors for locoregional control. It was also detected that age and haemoglobin level played as independent predictors for development of radiation toxicity. CONCLUSIONS: For patients with locally advanced oesophageal carcinoma undergone irradiation, anaemia associated a statistically significant reduction in survival and locoregional control rates, but also decreased radiation toxicity rates. Therefore, haemoglobin level should be considered as a stratification variable in prospective clinical trials.

Effect of IL-1ra on human dental pulp cells and pulpal inflammation.

AIM: This study was conducted to investigate the effect of interleukin-1 receptor antagonist (IL-1ra) on the LPS-induced interleukin-1beta (IL-1beta) synthesis in human dental pulp cells and to assess the role of IL-1ra in pulpal inflammation. METHODS: IL-1beta from human dental pulp cells (HDP) was measured by sandwich ELISA; IL-1ra expression in pulpal tissue was detected by immunohistochemical staining. RESULTS: Stimulation of HDP with increasing concentrations of FnLPS resulted in dose-dependent IL-1beta production. The addition of IL-1ra reduced FnLPS-induced IL-1beta synthesis in human dental pulp cells. Significant inhibition of the FnLPS-induced IL-1beta synthesis was observed when IL-1ra was added before treating with FnLPS for 60 min. Large numbers of IL-1ra positive neutrophils, plasmacytes, endothelial cells and lymphocytes were observed in inflamed pulp tissue. CONCLUSIONS: IL-1ra could reduce LPS-stimulated IL-1beta synthesis, suggesting that IL-1ra may play a role in pulpitis.

[Isolation and structure determination of xanthone glycosides of Anemarrhena asphodeloides].

Xilingzhimu, the rhizomes of Anemarrhena asphodeloides Bunge (Liliaceae), has been prescribed as antipyretic, anti-inflammatory, diuretic and hypoglycemic agents in Chinese traditional medicine. In this paper, two xanthone glycosides I and II, were isolated from Xilingzhimu by conventional method. The structures of I and II were identified on the basis of chemical reactions and UV, IR, 1HNMR, 13CNMR and DEPT. Compound I was identified as mangiferin and II is a new compound, named neomangiferin. Its structure is 7-O-beta-D-glucopyranosyl-mangiferin.

[Clinical observation on 112 cases with non-Hodgkin's lymphoma treated by Chinese herbs combined with chemotherapy].

OBJECTIVE: To seek for the effective therapeutical method in treating non-Hodgkin's lymphoma (NHL). METHODS: One hundred and sixty seven patients with non-Hodgkin's lymphoma were randomly divided into two groups, the treatment group, which consisted of 112 cases using Chinese herbs combined with chemotherapy and 55 cases of control group were treated by chemotherapy only. RESULTS: The effective rate (CR + PR) in the combined group was 91.96% and survival rates of 1-, 3- and 5-year were 85.7%, 54.5% and 29.5% respectively, and median survival time was 554 days. In control group the effective rate was 72.73% and 1-, 3- and 5-year survival rates were 76.4%, 38.2% and 18.2% respectively, and the median survival time was 465 days. The difference of effective rates or 3-year survival rates between two groups was significant (P < 0.05). In the combined group the activity of NK cell, OKT3, OKT4 and ratio of OKT4/OKT8 were obviously raised after treatment (P < 0.01). And the level of platelet adhesion rate and the blood viscosity markedly decreased (P < 0.01), but in the control group the values of these indexes did not distinctly change. CONCLUSION: Chinese herbs could enhance the immunologic function and improve the viscosity of blood of the patients with NHL. The side effect in the combination therapy group was less and milder than that in the chemotherapy group. These showed that Chinese herbs combined with chemotherapy was a safe and effective method for treating NHL and deserve to be recommended.

[Pars plana lensectomy and anterior vitrectomy for the treatment of congenital subluxated lenses].

The conventional surgical management of congenital subluxated lenses is frequently associated with a high incidence of complications leading to poor visual prognosis. Lensectomy through the pars plana with modern techniques of microsurgery and automated suction-cutting devices was performed on 11 patients (18 eyes) whose pre-operative visual acuities with the best optical correction ranged from 0.05-0.3, which were improved postoperatively to 0.5-1.0 during a follow-up of 3 to 60 months with an average of 36 months. The complications were accidental small cuts at the pupillary borders of 3 eyes, indicating that pars plana lensectomy is a safe procedure for the treatment of congenital subluxated lenses.

beta-deuterium kinetic isotope effects in the purine nucleoside phosphorylase reaction.

1. [2'-2H]Inosine was made from inosine by tetraisopropyldisiloxanyl protection of the 3'- and 5'-positions, oxidation with dimethyl sulphoxide and acetic anhydride, immediate NaB2H4 reduction of the oxo sugar product and inversion at C-2' of the resultant protected [2'-2H]arabino-inosine by trifluoromethanesulphonylation and reaction with caesium propionate, followed by deprotection. 2. The equilibrium-perturbation technique was used to measure beta 2H(V/K) for phosphorolysis of this compound by the purine nucleoside phosphorylase of Escherichia coli as a function of pH. 3. The pH variation indicates an intrinsic effect of 1.068 masked by isotopically silent steps near the pH optimum. 4. The similar pH variation of these beta-deuterium effects and the alpha-deuterium effects measured previously [Stein & Cordes (1981) J. Biol. Chem. 256, 767-772; Lehikoinen, Sinnott & Krenitsky (1989) Biochem. J. 257, 355-359] for this reaction provides the first experimental reassurance for the common assumption that pH changes merely mask and unmask the chemical steps in an enzyme-catalysed reaction, and do not detectably alter transition-state structure. 5. The dihedral angle between the C-H-2' bond and the electron-deficient p-orbital at the transition state is in the range 32-48 degrees, in accord with an essentially planar furanose ring.