Protein intake and its relationship with frailty in chronic kidney disease.

INTRODUCTION: Patients with chronic kidney disease (CKD) are susceptible to frailty because of a range of nutrition-related factors. While protein restriction is commonly advised to preserve kidney function in patients with CKD, insufficient protein intake could potentially exacerbate frailty risk. This study aimed to elucidate the relationship between frailty and protein intake in patients with CKD. METHODS: This cross-sectional study enrolled patients with CKD stage 3-5. Frailty and prefrailty were assessed using the Japanese version of the Cardiovascular Health Study (J-CHS) criteria. To estimate dietary protein intake, Maroni's formula based on 24-h urine collection was used. The potential association between frailty/pre-frailty and protein intake was investigated using a logistic regression analysis. RESULTS: Ninety-seven individuals with CKD were included in the study, with a median age of 73.0 years (interquartile range: 67.0, 82.0). Among them, 34 were women (35.1%), and the estimated glomerular filtration rate (eGFR) was 36.3 mL/min/1.73 m2 (interquartile range: 26.9, 44.1). Frailty and pre-frailty were identified in 13.4% and 55.7% of participants, respectively. Comparing the groups, protein intake in the frailty/pre-frailty group (0.83 g/kgBW/day [0.72, 0.93]) was lower than that in the robust group (0.89 g/kgBW/day [0.84, 1.19], p = 0.002). Upon logistic regression analysis, protein intake exhibited an independent association with frailty/pre-frailty (odds ratio: 0.72, 95% confidence interval: 0.59-0.89, p = 0.003). CONCLUSION: Reduced protein intake in patients with CKD is associated with frailty and pre-frailty. It is advisable to ensure that patients with CKD who are at risk of frailty consume an adequate amount of protein.

Low muscle strength and physical function contribute to falls in hemodialysis patients, but not muscle mass.

INTRODUCTION: Patients on hemodialysis (HD) have a higher incidence of fractures than the general population. Sarcopenia is frequently observed in patients on HD; however, the association of falls with sarcopenia and its diagnostic factors, including muscle mass, muscle strength, and physical function, are incompletely understood. METHODS: This prospective cohort study was conducted at a single center. Sarcopenia was assessed according to the 2019 Asian Working Group for Sarcopenia diagnostic criteria. Muscle mass was measured the bioelectrical impedance method. Grip strength was evaluated to assess muscle strength, while the Short Physical Performance Battery (SPPB) was used to assess physical function. Falls and their detailed information were surveyed every other week. RESULTS: This study analyzed 65 HD patients (median age, 74.5 [67.5-80.0] years; 33 women [49.2%]). Sarcopenia was diagnosed in 36 (55.4%) patients. During the 1-year observation period, 31 (47.7%) patients experienced accidental falls. The falls group had lower median grip strength than the non-falls group (14.7 [11.4-21.8] kg vs. 22.2 [17.9-27.6] kg; p < 0.001). The median SPPB score was also lower in the falls versus non-falls group (7.0 [5.0-11.0] vs. 11.0 [8.0-12.0]; p = 0.009). In adjusted multiple regression analysis, diagnostic factors, including grip strength (B = 0.96, p = 0.04, R2 = 0.19) and SPPB (B = 1.11, p = 0.006, R2 = 0.23), but not muscle mass, were independently associated with fall frequency. CONCLUSIONS: The frequency of falls in HD patients was related to muscle strength and physical function, but not muscle mass.

Dynamic and static balance functions in hemodialysis patients and non-dialysis dependent CKD patients.

INTRODUCTION: Chronic kidney disease (CKD) patients undergoing hemodialysis (HD) have a high risk of falls, whereas the impairment in balance function and their types in HD compared with non-dialysis dependent (ND) CKD have not been fully evaluated. METHODS: We conducted a cross-sectional study to assess the balance function in 91 ND-CKD and 65 HD patients. The participants underwent the timed up-and-go (TUG) test to assess dynamic balance and the length of the center of pressure (CoP) with open eyes or closed eyes to evaluate static balance. RESULTS: TUG, length of CoP with open eyes, and length of CoP with closed eyes were longer in HD patients compared with those with ND-CKD. Multiple regression analysis showed that dialysis treatment independently affected TUG and length of CoP with open eyes. CONCLUSION: The dynamic and static balance functions are impaired in HD patients compared with ND-CKD patients.

Dysfunction in dynamic, but not static balance is associated with risk of accidental falls in hemodialysis patients: a prospective cohort study.

BACKGROUND: Patients with chronic kidney disease undergoing hemodialysis (HD) have a high incidence of falls. Impairment of balance function is a risk factor for falls in the general elderly, and no report examining the association between balance dysfunction and fall incidence in HD patients exists. METHODS: This prospective cohort study was conducted at a single center. The timed-up-and-go test (TUG) as a dynamic balance function was performed and length of the center of pressure (CoP) as a static balance function was measured before and after the HD session at baseline. Data of the number and detailed information of accidental falls for 1 year were collected. Multiple regression analyses were performed to assess the relationships between the number of falls and balance function. RESULTS: Forty-three patients undergoing HD were enrolled in the study. During 1 year of observation, 24 (55.8%) patients experienced accidental falls. TUG time was longer, and CoP was shorter in the post-HD session than in the pre-HD session. Adjusted multiple regression analyses showed that the number of accidental falls was independently associated with TUG time in the pre-HD session (B 0.267, p < 0.001, R2 0.413) and that in the post-HD session (B 0.257, p < 0.001, R2 0.530), but not with CoP. CONCLUSIONS: Dynamic balance was associated with fall incidence in maintenance HD patients. The evaluation and intervention of dynamic balance function might reduce the risk of falls in HD patients. TRIAL REGISTRATION: This study was carried out with the approval of the Niigata Rinko Hospital Ethics Committee (approval number 2005-92) (Registered on December 11, 2019) and registered in The University Hospital Medical Information Network (registration number 000040618 ).

Comparison of muscle strength between hemodialysis patients and non-dialysis patients with chronic kidney disease.

[Purpose] Muscle weakness in patients with chronic kidney disease is associated with several disease-related factors, and this study aimed to examine whether hemodialysis is one of risk factors for muscle weakness in patients with chronic kidney disease. [Participants and Methods] We conducted a cross-sectional study with 74 non-dialysis and 84 hemodialysis patients. Muscle strength evaluations were performed by measuring isometric knee extensor muscle strength and grip strength. Each evaluation item was compared between the hemodialysis and non-dialysis groups, and multiple regression analysis was performed to determine the factors associated with muscle strength. In addition, the correlation between lower-extremity muscle strength and grip strength was examined in each group. [Results] Isometric knee extensor muscle strength was significantly lower in the hemodialysis group than in the non-dialysis group. Grip strength was also significantly lower in the hemodialysis group than in the non-dialysis group. Hemodialysis was determined to be an independent risk factor associated with lower limb muscle strength as well as grip strength. The positive correlation between isometric knee extensor muscle strength and grip strength was almost the same in the groups. [Conclusion] Hemodialysis treatment was an independent risk factor for muscle weakness. Regular monitoring of grip strength may facilitate better management with physical therapy in hemodialysis patients.

Feasibility of intermittent back-filtrate infusion hemodiafiltration to reduce intradialytic hypotension in patients with cardiovascular instability: a pilot study.

BACKGROUND: Intradialytic hypotension (IDH) is one of the major problems in performing safe hemodialysis (HD). As blood volume depletion by fluid removal is a major cause of hypotension, careful regulation of blood volume change is fundamental. This study examined the effect of intermittent back-filtrate infusion hemodiafiltration (I-HDF), which modifies infusion and ultrafiltration pattern. METHODS: Purified on-line quality dialysate was intermittently infused by back filtration through the dialysis membrane with a programmed dialysis machine. A bolus of 200 ml of dialysate was infused at 30 min intervals. The volume infused was offset by increasing the fluid removal over the next 30 min by an equivalent amount. Seventy-seven hypotension-prone patients with over 20-mmHg reduction of systolic blood pressure during dialysis or intervention-requirement of more than once a week were included in the crossover study of 4 weeks duration for each modality. In a total of 1632 sessions, the frequency of interventions, the blood pressure, and the pulse rate were documented. RESULTS: During I-HDF, interventions for symptomatic hypotension were reduced significantly from 4.5 to 3.0 (per person-month, median) and intradialytic systolic blood pressure was 4 mmHg higher on average. The heart rate was lower during I-HDF than HD in the later session. Older patients and those with greater interdialytic weight gain responded to I-HDF. CONCLUSIONS: I-HDF could reduce interventions for IDH. It is accompanied with the increased intradialytic blood pressure and the less tachycardia, suggesting less sympathetic stimulation occurs. Thus, I-HDF could be beneficial for some hypotension-prone patients. UMIN REGISTRATION NUMBER: 000013816.

Population pharmacokinetic analysis of thrombomodulin alfa to support dosing rationale in patients with renal impairment.

Thrombomodulin alfa is a soluble recombinant human thrombomodulin that was reported to enhance the reversal of disseminated intravascular coagulation (DIC) in subjects with sepsis or hematologic malignancy and reduce mortality in subjects with sepsis and DIC. Population pharmacokinetic (PK) analysis of thrombomodulin alfa was performed based on rich samples collected in 24 healthy subjects (0.02 and 0.06 mg/kg) and sparse samples collected in 368 subjects with sepsis and DIC (0.06 mg/kg). Sources of variability (baseline characteristics, markers of renal/liver function, hematocrit, and disease severity) were explored using non-linear mixed effect modeling to support dosing rationale in patients with sepsis and DIC. Plasma concentrations of thrombomodulin alfa were best fitted with a one-compartment model. Body weight and creatinine clearance were important covariates describing the PK of thrombomodulin alfa. Typical CL values in patients with normal renal function, or mild, moderate and severe renal impairment were 0.158, 0.145, 0.128, and 0.105 L/h, respectively. Based on simulations, a 0.06 mg/kg dosing of thrombomodulin alfa is expected to result in drug exposure within the therapeutic range of the product (300-5,400 ng/mL), with minimum risks of bleeding in patient with normal and impaired renal functions.

A case of endocapillary proliferative glomerulonephritis with macrophages phagocytosing monoclonal immunoglobulin lambda light chain.

Multiple myeloma (MM) is a plasma-cell neoplasm that can cause renal disorders. Renal lesions in MM can present with a very rare pathological manifestation involving a specific monoclonal immunoglobulin (Ig). We report the case of a 33-year-old woman who had edema, fatigue, elevated serum creatinine levels, hypoalbuminemia, and hypercholesterolemia. She had persistent hematuria and proteinuria lasting 3 years. Serum protein electrophoresis showed an M-spike, and serum immunofixation demonstrated the presence of monoclonal IgG λ. She had proteinuria in the nephrotic range, and a monoclonal λ fragment was present on urine immunofixation. Renal biopsy showed proliferative glomerulonephritis with λ light chain and C3c deposition and inflammatory cell infiltration with CD68. Macrophage lysosomes contained λ light chains, suggesting their partial phagocytosis. She was diagnosed with symptomatic MM and was treated with bortezomib and dexamethasone and an autologous peripheral stem cell transplant conditioned with intravenous melphalan. She achieved a partial response with decreased serum monoclonal protein and improved renal function. This case may be categorized as a monoclonal gammopathy-associated proliferative glomerulonephritis. The biopsy finding of partially phagocytosed Ig λ light chains by macrophages is very rare; this pathological condition is similar to crystal-storing histiocytosis.

Dysregulation of inflammatory and hemostatic markers in sepsis and suspected disseminated intravascular coagulation.

Inflammatory mediators and hemostatic markers were evaluated in patients enrolled in a phase-2b study evaluating the safety and efficacy of recombinant thrombomodulin (ART-123) in patients with sepsis and suspected disseminated intravascular coagulation (DIC). In contrast to controls, patients with sepsis and suspected DIC showed an increase in the circulating levels of inflammatory and fibrinolytic markers. The levels of procalcitonin (PCT), interleukin 6 (IL-6), interleukin 10 (IL-10), anaphylatoxin C5a, plasminogen activator inhibitor 1 (PAI-1), and myeloperoxidase were higher in the patients with sepsis and suspected DIC, whereas protein C (PrC) exhibited a significant decrease. When the patients with overt and nonovert DIC were compared, the PrC level was lower, and PCT, PAI-1, IL-6, and IL-10 levels were higher in the patients with overt DIC. These results indicate that inflammation is elevated in sepsis and suspected DIC, and inflammation, impairment of fibrinolysis, and overconsumption of PrC may play a key role in the pathogenesis of DIC.

Thrombin generation mediators and markers in sepsis-associated coagulopathy and their modulation by recombinant thrombomodulin.

Severe sepsis remains the most common cause of death in critically ill patients, and thrombin plays a crucial role in the pathogenesis of sepsis-associated disseminated intravascular coagulation (DIC). The purpose of this study was to profile prothrombin fragment (F1.2), thrombin-antithrombin complex (TAT), and d-dimer (DD) throughout the course of hospital stay in patients identified with sepsis. Plasma samples from patients enrolled in the ART-123 study, a phase 2b, international, multicenter, randomized placebo-controlled trial were analyzed for various parameters using enzyme-linked immunosorbent assay methods. Plasma levels of F1.2, DD, and TAT were measured at several time points following administration of recombinant thrombomodulin or placebo, and the results were tabulated. In the group treated with thrombomodulin, the median F1.2 levels demonstrated a 16% decrease from the baseline to day 7, while the placebo group showed an 8% increase. Both the treatment groups showed a gradual decrease in the TAT and DD, with the group treated with thrombomodulin demonstrating twice the decrease over the 7-day period. Although the data were widely scattered, these results show that DIC represents a hypercoagulable state along with other hemostatic abnormalities and the activation of the inflammatory process. Modulation of these activation processes through targets such as DD, F1.2, and TAT may play an important regulatory role in the pathogenesis of sepsis-associated coagulopathy. Moreover, this study validates the hypothesis that thrombomodulin downregulates the thrombin generation mediators/markers in sepsis-associated DIC.

The importance of medical interview with CKD patient in diagnoses of a family with Fabry disease.

A 47-year-old Japanese man was admitted to our hospital for evaluation of proteinuria, which was detected when he was 37 years of age. His creatinine clearance levels had fallen to 76.3 mL/min/1.73 m2. A kidney biopsy was conducted, and the patient's low plasma α-galactosidase A levels suggested Fabry disease. After genetic counseling, GLA analysis revealed a novel mutation p.L387P. Interview with the patient revealed that both his younger brother and mother suffered from cardiomyopathy and were undergoing cardiological treatment. They also were positive for proteinuria. About 30 years ago, the patient's cousin (aged 25) was diagnosed with Fabry disease. He underwent hemodialysis for 9 years until his death at 42. At that time, the patient and his brother had not been investigated for Fabry disease so their cousin could not act as a proband for the brothers. Eventually, the patient, his mother, and his brother were put on enzyme replacement therapy with agalsidase beta. As this series of cases shows, medical interviews to collate both medical and family history were essential for the discovery of Fabry disease in these patients. In addition, being a treatable genetic disorder, Fabry disease should be listed in the standard differential diagnoses of systemic and familial diseases, including unknown cause of nephropathy or cardiomyopathy, for early detection of the disorder.

A case of podocytic infolding glomerulopathy with focal segmental glomerulosclerosis.

Podocytic infolding glomerulopathy (PIG) has been proposed as a new disease entity. A 14-year-old girl underwent renal biopsy at our institution because of a chance finding of proteinuria. Light microscopic findings revealed a minor glomerular abnormality, but under a higher magnification, after periodic acid methenamine silver staining, a bubbling appearance in the glomerular basement membrane (GBM) was observed. An electron microscopic examination revealed microspheres in the GBM, which were sparse but global. The patient was diagnosed as having PIG. After 3 years, her urinary protein had increased and a second biopsy was performed, showing focal segmental glomerulosclerosis in addition to a lesser degree of podocytic infolding than at the first biopsy. This is the first report of a case complicated by a different type of glomerulonephritis after being diagnosed as PIG. A few cases of PIG are complicated by focal segmental glomerulosclerosis, suggesting several mechanisms for the disorder.

A randomized, double-blind, placebo-controlled, Phase 2b study to evaluate the safety and efficacy of recombinant human soluble thrombomodulin, ART-123, in patients with sepsis and suspected disseminated intravascular coagulation.

OBJECTIVES: To determine the safety and efficacy of recombinant thrombomodulin (ART-123) in patients with suspected sepsis-associated disseminated intravascular coagulation. DESIGN: Phase 2b, international, multicenter, double-blind, randomized, placebo-controlled, parallel group, screening trial. SETTING: Two hundred and thirty-three ICUs in 17 countries. PATIENTS: All adult patients admitted with sepsis and suspected disseminated intravascular coagulation as assessed using a modified International Society on Thrombosis and Hemostasis score. INTERVENTIONS: Patients were randomized to receive IV ART-123 (0.06 mg/kg/d) for 6 days or placebo, in addition to standard of care. The primary endpoint was reduction in mortality. Secondary endpoints included reversal of overt disseminated intravascular coagulation and reduction in disease severity. MEASUREMENTS AND MAIN RESULTS: A total of 750 patients were randomized, nine of whom did not receive the allocated treatment so that 371 patients received ART-123 and 370 received placebo. There were no meaningful differences between the two groups in any of the baseline variables. Twenty-eight-day mortality was 17.8% in the ART-123 group and 21.6% in the placebo group (Cochran-Mantel-Haenszel two-sided p value of 0.273 in favor of ART-123, which met the predefined statistical test for evidence suggestive of efficacy). There were no statistically significant differences in event-free and alive days between the two groups. d-dimer, prothrombin fragment F1.2 and TATc concentrations were lower in the ART-123 group than in the placebo group. There were no differences between the two groups in organ function, inflammatory markers, bleeding or thrombotic events or in the development of new infections. In post hoc analyses, greatest benefit from ART-123 was seen in patients with at least one organ system dysfunction and an international normalized ratio greater than 1.4 at baseline. CONCLUSIONS: ART-123 is a safe intervention in critically ill patients with sepsis and suspected disseminated intravascular coagulation. The study provided evidence suggestive of efficacy supporting further development of this drug in sepsis-associated coagulopathy including disseminated intravascular coagulation. Future study should focus on using ART-123 in the subgroup of patients most likely to respond to this agent.

Pentraxin-3 expression in acute renal allograft rejection.

Pentraxin-3 (PTX3) is an acute phase reactant produced by a variety of cell types at sites of local inflammation. We examined by immunohistochemistry renal biopsies from patients with acute rejection (n = 10), protocol biopsies without rejection (n = 37), and peri-operative donor biopsies of the same transplant patients (n = 94) for intra-renal expression of PTX3, and its correlation with clinical, laboratory, and histopathologic parameters. PTX3 was mainly expressed in the interstitium of renal allograft. In the non-rejection biopsies (pre- and post-reperfusion and protocol biopsies), PTX3 expression area (PTX3%) was equally maintained at a low level, whereas in the rejection biopsies, PTX3% was significantly higher (p < 0.0001). Treatment of acute rejection resulted in a significant reduction of PTX3% (p < 0.0001). PTX3% positively correlated with the degree of allograft dysfunction and acute rejection scores of Banff classification (2009). This study suggests that PTX3% may be an available histological marker of acute renal allograft rejection.

[Changes in the prognosis for survival of patients with end-stage renal disease (ESRD) treated by hemodialysis].

UNLABELLED: We started dialysis treatment in our institution in 1966, and have improved hemodialysis (HD) treatment through the induction of a biocompatible dialysis membrane, recombinant human erythropoietin, activated vitamin D and purification of the dialysate. We verified improvement of the prognosis for survival of patients with ESRD during this forty-year period, retrospectively. A total of 1,690 patients who began dialysis therapy in our hospital between January 1966 and December 2005 was studied (men: 1,047, women: 643, age: 58.6 +/- 17.4 years. They were divided into four groups (A: patients who started dialysis in the period from 1966 to 1975; n = 280, B: 1976-1985; n = 455, C: 1986-1995; n = 499, D: 1996-2005; n = 456). The mean follow-up period was 8.48 +/- 8.53 years. Of the patients 1,588 were treated with HD, 78 with peritoneal dialysis (PD), and 24 with PD or HD. Age at the initiation of dialysis increased gradually (A: 40.1 +/- 14.2 y-o, B: 53.2 +/- 15.8 y-o, C: 60.0 +/- 16.0 y-o, D: 66.4 +/- 13.8 y-o), and diabetics increased (A: 6.4%, B: 19.5%, C: 25.6%, D: 33.4%). A total of 1,180 patients died; 48.5% of these patients died of cardiovascular disease, 21.3% of infectious disease, and 6.4% of malignancy. Only 13 patients had kidney-transplants. With the Cox proportional hazard model for HD cases, age at the initiation of dialysis, gender, cause of renal disease, and the periods were significant predictors of mortality. The relative risk of mortality compared with that in A was reduced progressively: 0.796 in period B (95% confidence interval [CI]: 0.659-0.961, p = 0.0178), 0.505 in period C (95% CI: 0.409-0.623, p < 0.0001), and 0.286 in period D (95% CI: 0.223-0.366, p < 0.0001). CONCLUSIONS: Although the number of high-aged patients or diabetics with ESRD increased in these 40 years, the survival of the patients with ESRD improved.

Calcium and phosphorus control in patients undergoing hemodialysis: from the view-points of activities of daily living.

To determine the compliance with the JSDT guidelines and activities of daily living (ADLs), phosphorus levels, calcium levels and Barthel index of patients under maintenance hemodialysis therapy in Shinrakuen hospital at December 2005 were evaluated. Of 369 patients, 28.7 % were controlled in the range of JSDT guidelines both phosphorus and calcium. Administration of sevelamer hydrochloride were low both in number of patients and also of using dose. Barthel index were higher in the patients with high phosphorus levels and low calcium level. Patients mortality at February 2007 was highest in the group of low phosphorus and high calcium levels in which the ADLs were the lowest. Concerned about vascular complication, patients in the group with target level or higher level of calcium and phosphorus were frequently noted.

[Serum calcium levels at first renal replacement therapy and patients survival].

In K/DOQI guideline, albumin adjusted serum calcium concentrations between 8.4 to 9.5 mg/dL and serum phosphorus concentrations between 3.5 to 5.5 mg/dL are recommended. But without clinical symptoms relating to hypocalcemia, medication for increasing serum calcium levels is not needed even less than 8.4 mg/dL. To clarify this guideline, we examined the data of 271 patients who started dialysis at Shinrakuen Hospital, their medication before renal replacement therapy and life prognosis. Medication made higher serum calcium concentrations (p< 0.005) at first renal replacement therapy. Concerning serum calcium concentrations, the lower group (<8.4 mg/dL) showed significantly better prognosis than the middle group (8.4 to 9.5 mg/dL) and the higher group (>9.5 mg/dL) (p< 0.05). When serum calcium levels were adjusted for the level of serum albumin, this tendency was stronger (p< 0.0001). We concluded that although serum calcium concentrations might not need control, nutritional states are far more important before starting dialysis.

Renal function at the time of renal biopsy as a predictor of prognosis in patients with primary AL-type amyloidosis.

BACKGROUND: Amyloid light-chain (AL)-type amyloidosis is a plasma cell disorder with a poor prognosis for survival. Although prognostic factors, such as the number of organs involved and heart function or failure in respond to therapy have been clarified based on studies including a large series of patients, there are large interindividual differences in the prognosis of patients with primary AL-type renal amyloidosis. METHODS: To clarify the prognostic factors of AL-type renal amyloidosis, we retrospectively investigated the clinical manifestations, histopathological data, and prognosis of 21 patients with amyloidosis, who had been diagnosed by renal biopsy. RESULTS: Eleven patients died, at a mean observational time of 21.7 months after renal biopsy, whereas the mean observational time was 51.0 months for the 10 patients who survived. The creatinine clearance rate was significantly higher, and the serum creatinine concentration and the grade of interstitial damage were significantly lower in surviving patients (P < 0.05). The presence of amyloid fibrils in organs other than the kidney did not influence prognosis for survival. However, the intraventricular septum was thinner in surviving patients (P < 0.1). Thirteen patients had undergone melphalan-prednisolone therapy, but it did not affect prognosis for survival. Cox proportional hazard regression analysis revealed that the renal function at the time of diagnosis was a significant and independent prognostic factor for survival. CONCLUSIONS: Our study demonstrated that renal function at the time of biopsy and renal interstitial damage are the best predictors of survival in AL-type renal amyloidosis.

In vitro selection of RNA aptamers that bind to colicin E3 and structurally resemble the decoding site of 16S ribosomal RNA.

Colicin E3 is a ribonuclease that specifically cleaves at the site after A1493 of 16S rRNA in Escherichia coli ribosomes, thus inactivating translation. To analyze the interaction between colicin E3 and 16S rRNA, we used in vitro selection to isolate RNA ligands (aptamers) that bind to the C-terminal ribonuclease domain of colicin E3, from a degenerate RNA pool. Although the aptamers were not digested by colicin E3, they specifically bound to the protein (K(d) = 2-14 nM) and prevented the 16S rRNA cleavage by the C-terminal ribonuclease domain. Among these aptamers, aptamer F2-1 has a sequence similar to that of the region around the cleavage site from residue 1484 to 1506, including the decoding site, of E. coli 16S rRNA. The secondary structure of aptamer F2-1 was determined by the base pair covariation among the variants obtained by a second in vitro selection, using a doped RNA pool based on the aptamer F2-1 sequence. The sequence and structural similarities between the aptamers and 16S rRNA provide insights into the recognition of colicin E3 by this specific 16S rRNA region.