Bleeding Risk With Cold Snare Polypectomy of ≤10 mm Pedunculated Colon Polyps.

OBJECTIVES: Pedunculated polyps (PPs) in the colon are usually resected with hot snare polypectomy to prevent immediate postpolypectomy bleeding (IPPB). This study aimed to evaluate the safety of CSP of <10 mm PPs. MATERIALS AND METHODS: Patients undergoing colonoscopy from February 18, 2019, to April 24, 2020, and were found to have at least 1 ≤10 mm PP resected with CSP were included prospectively in a continuous quality improvement project to assess the risk of IPPB and delayed postpolypectomy bleeding. Polyp location, size, and pathology, as well as the method of resection, were recorded. In addition, we assessed the occurrence and severity of IPPB and the need for intervention. RESULTS: We found 239 eligible polyps in 182 patients. The mean (SD) age was 58.8 (8.3) years, and 61% were males. IPPB occurred in 72 of 239 polyps, corresponding to a per-polyp bleeding percentage of 30.1% and in 65 of 182 patients, equating to a per-patient bleeding rate of 35.7%. We successfully treated bleeding by endoscopic hemostasis in 57%; the remaining 31 polyps (43%) did not require endoscopic intervention. There was no association between IPPB with age, gender, or use of aspirin or antithrombotic agents. In the bivariate model, polyp size and pathology were not associated with the risk of IPPB. Right-sided polyps were associated with a reduced risk of IPPB in the bivariate model by 61% (odds ratio=0.39; 95% confidence interval, 0.21-0.74; P =0.0057). In the multivariate model, choking the polyp base decreased the likelihood of IPPB by 97% (odds ratio=0.03; 95% confidence interval, 0.00-0.86; P =0.0459). There were no instances of delayed bleeding, perforation, or postpolypectomy syndrome. CONCLUSIONS: CSP can be used for resection of ≤10 mm PPs. It is associated with a lower risk of immediate bleeding than the common perception among gastroenterologists.

Narrow-band imaging versus white light for the detection of proximal colon serrated lesions: a randomized, controlled trial.

BACKGROUND: The value of narrow-band imaging (NBI) for detecting serrated lesions is unknown. OBJECTIVE: To assess NBI for the detection of proximal colon serrated lesions. DESIGN: Randomized, controlled trial. SETTING: Two academic hospital outpatient units. PATIENTS: Eight hundred outpatients 50 years of age and older with intact colons undergoing routine screening, surveillance, or diagnostic examinations. INTERVENTIONS: Randomization to colon inspection in NBI versus white-light colonoscopy. MAIN OUTCOME MEASUREMENTS: The number of serrated lesions (sessile serrated polyps plus hyperplastic polyps) proximal to the sigmoid colon. RESULTS: The mean inspection times for the whole colon and proximal colon were the same for the NBI and white-light groups. There were 204 proximal colon lesions in the NBI group and 158 in the white light group (P = .085). Detection of conventional adenomas was comparable in the 2 groups. LIMITATIONS: Lack of blinding, endoscopic estimation of polyp location. CONCLUSION: NBI may increase the detection of proximal colon serrated lesions, but the result in this trial did not reach significance. Additional study of this issue is warranted. ( CLINICAL TRIAL REGISTRATION NUMBER: NCT01572428.).

Predictors of self- and caregiver-rated quality of life for people with dementia living in the community and in nursing homes in northern Taiwan.

BACKGROUND: Factors affecting quality of life (QOL) ratings for people with dementia (PWD) have been well studied, but few studies have examined the effect of residence on PWD- and caregiver-rated QOL for PWDs. We designed this study to determine the factors related to PWD- and caregiver-rated QOL in dementia as well as factors related to the discrepancy in these ratings. METHODS: For this cross-sectional study, we analyzed data from a convenience sample of 106 PWD-family caregiver dyads (58 community-dwelling dyads and 48 nursing-home dyads). PWDs' data included socio-demographic variables, QOL (assessed by the Quality of Life-Alzheimer's Disease [QOL-AD] scale), cognition, dementia severity, depression, comorbidities, and quality of the dyadic relationship. Caregivers' data included socio-demographic variables, depressive symptoms, and mutuality of the dyadic relationship. RESULTS: QOL-AD scores were lower when rated by caregivers than by PWDs. The key factors positively related to both PWD- and caregiver-rated QOL for PWDs were fewer PWD depressive symptoms and higher quality of the PWD-caregiver relationship. The key factors related to the discrepancy in PWD- and caregiver-rated QOL in dementia were PWD residence in a nursing home and lower dementia severity, as well as higher caregiver depression, being an adult child caregiver, and lower caregiver-PWD mutuality. CONCLUSION: Caregiver-rated QOL for PWDs and the discrepancy in rated QOL were significantly associated with PWD residence. If caregiver-rated QOL is needed, the effect of residence of PWD should be taken into consideration. Caregivers' depressive status and mutuality with PWD must be also carefully assessed.

Inversion recovery and saturation recovery pulmonary vein MR angiography using an image based navigator fluoro trigger and variable-density 3D cartesian sampling with spiral-like order.

Contrast enhanced pulmonary vein magnetic resonance angiography (PV CE-MRA) has value in atrial ablation pre-procedural planning. We aimed to provide high fidelity, ECG gated PV CE-MRA accelerated by variable density Cartesian sampling (VD-CASPR) with image navigator (iNAV) respiratory motion correction acquired in under 4 min. We describe its use in part during the global iodinated contrast shortage. VD-CASPR/iNAV framework was applied to ECG-gated inversion and saturation recovery gradient recalled echo PV CE-MRA in 65 patients (66 exams) using .15 mmol/kg Gadobutrol. Image quality was assessed by three physicians, and anatomical segmentation quality by two technologists. Left atrial SNR and left atrial/myocardial CNR were measured. 12 patients had CTA within 6 months of MRA. Two readers assessed PV ostial measurements versus CTA for intermodality/interobserver agreement. Inter-rater/intermodality reliability, reproducibility of ostial measurements, SNR/CNR, image, and anatomical segmentation quality was compared. The mean acquisition time was 3.58 ± 0.60 min. Of 35 PV pre-ablation datasets (34 patients), mean anatomical segmentation quality score was 3.66 ± 0.54 and 3.63 ± 0.55 as rated by technologists 1 and 2, respectively (p = 0.7113). Good/excellent anatomical segmentation quality (grade 3/4) was seen in 97% of exams. Each rated one exam as moderate quality (grade 2). 95% received a majority image quality score of good/excellent by three physicians. Ostial PV measurements correlated moderate to excellently with CTA (ICCs range 0.52-0.86). No difference in SNR was observed between IR and SR. High quality PV CE-MRA is possible in under 4 min using iNAV bolus timing/motion correction and VD-CASPR.

Effects of Phosphate and Two-Stage Sous-Vide Cooking on Textural Properties of the Beef Semitendinosus.

Comparing the effects of sodium tripolyphosphate (STPP) concentrations of 0.2% and 0.4% on beef semitendinosus is the objective of the current investigation. The samples were cooked at varied temperatures (45+60°C and 45+70°C) and times (1.5+1.5 h and 3+3 h) using staged cooking. The colour properties, cooking loss, water retention, shear force, water-holding capacity, sarcoplasmic, and myofibrillar solubility, and total collagen were investigated. The cooking time and temperature affected the water-holding capacity, cooking loss, CIE L*, CIE a*, CIE b*, myofibrillar, and sarcoplasmic solubility, with lower temperature and short time having the lower detrimental effect. However, the significant effect can be intensified after the addition of STPP with higher water-holding capacity and tender meat obtained with 0.4% phosphate concentration at any cooking conditions. The STPP lowered the collagen content and increased the protein solubility of myofibrillar and sarcoplasmic, which this degradation is used as a good indicator of tenderness.

Evaluating the Efficiency of Magnetic Treatment for Feed Water in Reverse Osmosis Processes.

The paper presents a new methodology for short-term (5-25 min) benchtop tests to evaluate the effectiveness of magnetic treatment of feed water for reducing mineral scaling on a reverse osmosis (RO) membrane. Scale deposition is measured at a controlled level of salt supersaturation in water flowing through an RO unit in once-through mode. A magnetic water conditioner is tested in a transient flow regime when variations of the permeate flux along the flow path are insignificant. Scale formation under these conditions is governed by salt crystallization on the membrane surface. The proposed method was implemented to investigate the influence of magnetic treatment on gypsum deposition on RO membranes in supersaturated aqueous CaSO4/NaCl solutions. The effects of magnetic water treatment on scale formation under our experimental conditions were found to be statistically insignificant with a confidence level of 95%. However, this outcome should not be considered to negate the potential efficiency of magnetic water treatment in specific applications. The proposed methodology of testing under a controlled level of salt supersaturation will also be useful for evaluating the efficiency of other water treatment technologies.

An Immunomodulatory Polysaccharide-Protein Complex Isolated from the Polypore Fungus Royoporus badius.

Many wild edible polypore mushrooms have medicinal value. In this study, we investigate the potential medicinal properties of the wild polypore mushroom Royoporus badius collected from north-central British Columbia, Canada. Water extract from R. badius was found to exhibit potent immunomodulatory activity. The extract was purified using DEAE-Sephadex anion-exchange chromatography as well as Sephacryl S-500 and HPLC BioSEC5 size-exclusion chromatography, to yield a novel polysaccharide-protein complex (IMPP-Rb).IMPP-Rb has a peak maxima molecular weight (Mp) of 950 kDa. GC-MS analyses showed that IMPP-Rb is composed predominantly of glucose (49.2%), galactose (11.3%), mannose (10.8%), rhamnose (9.6%), and galacturonic acid (8.2%), with smaller amounts of xylose (5.2%), fucose (2.8%), N-acetyl glucosamine (1.8%), and arabinose (1.2%). IMPP-Rb has multiple linkages, with 4-Glcp, 4-Manp, 6-Manp, 3,4-Manp, 4-Xylp, and 2-Rhap being the most prominent. IMPP-Rb is capable of inducing many cytokines in vitro and the protein component is indispensable for its immunomodulatory activity. IMPP-Rb has potential application as an immuno-stimulatory agent with pharmaceutical value.

Single-channel measurements of an N-acetylneuraminic acid-inducible outer membrane channel in Escherichia coli.

NanC is an Escherichia coli outer membrane protein involved in sialic acid (Neu5Ac, i.e., N-acetylneuraminic acid) uptake. Expression of the NanC gene is induced and controlled by Neu5Ac. The transport mechanism of Neu5Ac is not known. The structure of NanC was recently solved (PDB code: 2WJQ) and includes a unique arrangement of positively charged (basic) side chains consistent with a role in acidic sugar transport. However, initial functional measurements of NanC failed to find its role in the transport of sialic acids, perhaps because of the ionic conditions used in the experiments. We show here that the ionic conditions generally preferred for measuring the function of outer-membrane porins are not appropriate for NanC. Single channels of NanC at pH 7.0 have: (1) conductance 100 pS to 800 pS in 100 mM: KCl to 3 M: KCl), (2) anion over cation selectivity (V (reversal) = +16 mV in 250 mM: KCl || 1 M: KCl), and (3) two forms of voltage-dependent gating (channel closures above ± 200 mV). Single-channel conductance decreases by 50% when HEPES concentration is increased from 100 µM: to 100 mM: in 250 mM: KCl at pH 7.4, consistent with the two HEPES binding sites observed in the crystal structure. Studying alternative buffers, we find that phosphate interferes with the channel conductance. Single-channel conductance decreases by 19% when phosphate concentration is increased from 0 mM: to 5 mM: in 250 mM: KCl at pH 8.0. Surprisingly, TRIS in the baths reacts with Ag|AgCl electrodes, producing artifacts even when the electrodes are on the far side of agar-KCl bridges. A suitable baseline solution for NanC is 250 mM: KCl adjusted to pH 7.0 without buffer.

Components in time-varying graphs.

Real complex systems are inherently time-varying. Thanks to new communication systems and novel technologies, today it is possible to produce and analyze social and biological networks with detailed information on the time of occurrence and duration of each link. However, standard graph metrics introduced so far in complex network theory are mainly suited for static graphs, i.e., graphs in which the links do not change over time, or graphs built from time-varying systems by aggregating all the links as if they were concurrent in time. In this paper, we extend the notion of connectedness, and the definitions of node and graph components, to the case of time-varying graphs, which are represented as time-ordered sequences of graphs defined over a fixed set of nodes. We show that the problem of finding strongly connected components in a time-varying graph can be mapped into the problem of discovering the maximal-cliques in an opportunely constructed static graph, which we name the affine graph. It is, therefore, an NP-complete problem. As a practical example, we have performed a temporal component analysis of time-varying graphs constructed from three data sets of human interactions. The results show that taking time into account in the definition of graph components allows to capture important features of real systems. In particular, we observe a large variability in the size of node temporal in- and out-components. This is due to intrinsic fluctuations in the activity patterns of individuals, which cannot be detected by static graph analysis.

An evaluation study of a dementia screening program in Taiwan: an application of the theory of planned behaviors.

A challenge facing dementia service providers is how to detect dementia early to facilitate timely intervention. This article reports findings of an evaluation study of a dementia-screening program in Taiwan utilizing the Theory of Planned Behaviors. We present the Short Portable Mental Status Questionnaire (SPMSQ) program rationale and examine the effects of this important health and social service intervention. Follow-up telephone interviews were completed by 108 respondents. Findings indicate that the SPMSQ program was successful in identifying suspected dementia. Results also show that the dementia-screening program contributed to an increase in medical service utilization and in unpaid informal care.

Indirect organogenesis for high frequency shoot regeneration of two cultivars of Sansevieria trifasciata Prain differing in fiber production.

Sansevieria trifasciata is used as an indoor plant, in traditional medicine and as a fiber source. Here we characterized fibers of two of varieties of S. trifasciata, Lorentii and Hahnii, and report a protocol for their propagation based on indirect shoot organogenesis. Structural and ribbon fibers were scattered within leaf parenchyma when viewed with confocal laser scanning microscopy. Chemical analysis of the fibers by mass spectrometry and high-performance chromatography revealed higher contents of cellulose and xylose in Lorentii than in Hahnii and significant differences for total lignin between both. A protocol for de novo shoot production was then developed using leaf explants. Time-course histological analyses showed that the first events of transdifferentiation were triggered preferentially in cells surrounding fibers and vascular bundles. Callogenesis and shoot performances were quantified for both varieties, and 2,4-D at 2 and 3 mg·L-1 yielded the best results for primary calli induction and fresh calli mass. The length, number, and mass of shoots produced did not differ significantly between the two cultivars. The fast morphogenic response of S. trifasciata to in vitro culture may be useful for mass propagation or other biotechnological purposes such as metabolite production.

Transcriptome Mining Provides Insights into Cell Wall Metabolism and Fiber Lignification in Agave tequilana Weber.

Resilience of growing in arid and semiarid regions and a high capacity of accumulating sugar-rich biomass with low lignin percentages have placed Agave species as an emerging bioenergy crop. Although transcriptome sequencing of fiber-producing agave species has been explored, molecular bases that control wall cell biogenesis and metabolism in agave species are still poorly understood. Here, through RNAseq data mining, we reconstructed the cellulose biosynthesis pathway and the phenylpropanoid route producing lignin monomers in A. tequilana, and evaluated their expression patterns in silico and experimentally. Most of the orthologs retrieved showed differential expression levels when they were analyzed in different tissues with contrasting cellulose and lignin accumulation. Phylogenetic and structural motif analyses of putative CESA and CAD proteins allowed to identify those potentially involved with secondary cell wall formation. RT-qPCR assays revealed enhanced expression levels of AtqCAD5 and AtqCESA7 in parenchyma cells associated with extraxylary fibers, suggesting a mechanism of formation of sclerenchyma fibers in Agave similar to that reported for xylem cells in model eudicots. Overall, our results provide a framework for understanding molecular bases underlying cell wall biogenesis in Agave species studying mechanisms involving in leaf fiber development in monocots.

Dr Google, MD: a survey of mental health-related internet use in a private practice sample.

OBJECTIVE: The aim of this study was to evaluate the use of the internet to access mental health-related information in a private practice sample, and to understand how this influenced health behaviours in this group. METHOD: We undertook a cross-sectional survey of adult outpatients attending two group psychiatric practices. The content included internet usage, types of information located, disclosure with treating psychiatrist, and perceived influence on decision-making. We collected both quantitative and qualitative data. RESULTS: The internet was often used to access mental health-related information. Respondents most commonly looked for information about symptoms, treatment, side effects and diagnoses. Approximately one-third of those who sought mental health information on the internet discussed this with their psychiatrist, and those who did so were more likely to report an influence of this information on their decision-making. Respondents' comments suggested an appreciation of the utility of the internet, combined with an understanding of its limitations. CONCLUSION: Private practice patients frequently access mental health information from the internet. When discussed within the therapeutic setting, it appears more likely to influence health-related decision-making. As part of ongoing therapy, clinicians should actively discuss what patients have read on the internet.

Unravelling Chemical Composition of Agave Spines: News from Agave fourcroydes Lem.

Spines are key plant modifications developed to deal against herbivores; however, its physical structure and chemical composition have been little explored in plant species. Here, we took advantage of high-throughput chromatography to characterize chemical composition of Agave fourcroydes Lem. spines, a species traditionally used for fiber extraction. Analyses of structural carbohydrate showed that spines have lower cellulose content than leaf fibers (52 and 72%, respectively) but contain more than 2-fold the hemicellulose and 1.5-fold pectin. Xylose and galacturonic acid were enriched in spines compared to fibers. The total lignin content in spines was 1.5-fold higher than those found in fibers, with elevated levels of syringyl (S) and guaiacyl (G) subunits but similar S/G ratios within tissues. Metabolomic profiling based on accurate mass spectrometry revealed the presence of phenolic compounds including quercetin, kaempferol, (+)-catechin, and (-)-epicatechin in A. fourcroydes spines, which were also detected in situ in spines tissues and could be implicated in the color of these plants' structures. Abundance of (+)-catechins could also explain proanthocyanidins found in spines. Agave spines may become a plant model to obtain more insights about cellulose and lignin interactions and condensed tannin deposition, which is valuable knowledge for the bioenergy industry and development of naturally dyed fibers, respectively.

Determinants of the discrepancy in patient- and caregiver-rated quality of life for persons with dementia.

AIMS: To determine factors related to the discrepancy in patient- and proxy-rated quality of life for patients with dementia; whether this discrepancy is associated with characteristics of patients, caregivers or the caregiver-patient relationship; and which characteristics best predict this discrepancy. BACKGROUND: To increase the reliability of quality of life measurements for persons with dementia, many researchers have incorporated proxy reports. However, their investigations have indicated that caregiver-rated quality of life is not the same as the patient's own rating. The factors related to this discrepancy have previously been explored, but studies rarely focussed on the quality of the caregiver-patient relationship as a determinant of the discrepancy. DESIGN: A cross-sectional design was used. METHODS: Data were gathered from community-based interviews with 120 dyads of patients with Alzheimer's disease or related dementia and their caregivers in Taipei. A structured questionnaire was used to collect data, and the main variable (quality of life-Alzheimer's disease) was rated separately by patients and caregivers. The data were analysed using intraclass correlation coefficients and multivariate regression methods. RESULTS: The agreement between patients' and caregivers' quality of life-Alzheimer's disease ratings was low. This discrepancy was significantly associated with disturbing dementia behaviour, caregivers' perceived distress for problem behaviours, caregivers' overall quality of life and quality of the caregiver-patient relationship. CONCLUSIONS: The observed discrepancy between caregiver- and patient-rated quality of life for persons with dementia was largely predicted by the quality of the caregiver-patient relationship. RELEVANCE TO CLINICAL PRACTICE: Medical professionals should cautiously deliberate when using caregiver-reported quality of life to substitute for patient-reported quality of life. When using a proxy report or a combined caregiver-patient rating, medical professionals should assess the quality of the relationship between patient and proxy.

Skeletal macro- and microstructure adaptations in men undergoing arduous military training.

PURPOSE: Short periods of basic military training increase the density and size of the tibia, but the adaptive response of bone microarchitecture, a key component of bone strength, is not fully understood. METHODS: Tibial volumetric bone mineral density (vBMD), geometry, microarchitecture and mechanical properties were measured using high-resolution peripheral quantitative computed tomography in 43 male British Army infantry recruits (mean ±â€¯SD, age 21 ±â€¯3 years, height 1.76 ±â€¯0.06 m, body mass 76.5 ±â€¯9.4 kg). Bilateral scans were performed at the distal tibia at the start (week 1) and end (week 13) of basic military training. Concurrent measures were obtained for whole-body areal bone mineral density (aBMD) using DXA, and markers of bone metabolism (ßCTX, P1NP, PTH, total 25(OH)D and ACa) from venous blood. RESULTS: Training increased areal BMD for total body (1.4%) and arms (5.2%) (P ≤ 0.031), but not legs and trunk (P ≥ 0.094). Training increased trabecular (1.3 to 1.9%) and cortical vBMD (0.6 to 0.9%), trabecular volume (1.3 to 1.9%), cortical thickness (3.2 to 5.2%) and cortical area (2.6 to 2.8%), and reduced trabecular area (-0.4 to -0.5%) in both legs (P < 0.001). No changes in trabecular number, thickness and separation, cortical porosity, stiffness or failure load were observed (P ≥ 0.188). ßCTX decreased (-0.11 µg∙l-1, P < 0.001) and total 25(OH)D increased (9.4 nmol∙l-1, P = 0.029), but no differences in P1NP, PTH or ACa were observed between timepoints (P ≥ 0.233). CONCLUSION: A short period of basic military training increased density and altered geometry of the distal tibia in male military recruits. The osteogenic effects of basic military training are likely due to an increase in unaccustomed, dynamic and high-impact loading.

Single-bubble water boiling on small heater under Earth's and low gravity.

Today's trends for enhancing boiling heat transfer in terrestrial and space applications focus on removal of bubbles to prevent formation of a vapor layer over the surface at high overheat. In contrast, this paper presents a new boiling regime that employs a vapor-air bubble residing on a small heater for minutes and driving cold water over the surface to provide high heat flux. Single-bubble boiling of water was investigated under normal gravity and low gravity in parabolic flights. Experiments demonstrated a negligible effect of gravity level on the rate of heat transfer from the heater. Due to self-adjustment of the bubble size, the heat flux provided by boiling rose linearly up with increasing heater temperature and was not affected by a gradually rising water temperature. The fast response and stable operation of single-bubble boiling over a broad range of temperatures pave the way for development of new devices to control heat transfer by forming surface domains with distinct thermal properties and wettability. The bubble lifetime can be adjusted by changing the water temperature. The ability of heating water on millimeter scales far above 100 °C without an autoclave or a powerful laser provides a new approach for processing of biomaterials and chemical reactions.

Real-time cardiac MRI with radial acquisition and k-space variant reduced-FOV reconstruction.

This work aims to demonstrate that radial acquisition with k-space variant reduced-FOV reconstruction can enable real-time cardiac MRI with an affordable computation cost. Due to non-uniform sampling, radial imaging requires k-space variant reconstruction for optimal performance. By converting radial parallel imaging reconstruction into the estimation of correlation functions with a previously-developed correlation imaging framework, Cartesian k-space may be reconstructed point-wisely based on parallel imaging relationship between every Cartesian datum and its neighboring radial samples. Furthermore, reduced-FOV correlation functions may be used to calculate a subset of Cartesian k-space data for image reconstruction within a small region of interest, making it possible to run real-time cardiac MRI with an affordable computation cost. In a stress cardiac test where the subject is imaged during biking with a heart rate of >100 bpm, this k-space variant reduced-FOV reconstruction is demonstrated in reference to several radial imaging techniques including gridding, GROG and SPIRiT. It is found that the k-space variant reconstruction outperforms gridding, GROG and SPIRiT in real-time imaging. The computation cost of reduced-FOV reconstruction is ~2 times higher than that of GROG. The presented work provides a practical solution to real-time cardiac MRI with radial acquisition and k-space variant reduced-FOV reconstruction in clinical settings.

AC conductance of transmembrane protein channels. The number of ionized residue mobile counterions at infinite dilution.

Simultaneous measurements of the AC and DC conductances of alpha-hemolysin (alphaHL) ion channels and outer membrane protein F (OmpF) porins in dilute ionic solutions is described. AC conductance measurements were performed by applying a 10 mV rms AC voltage across a suspended planar bilayer of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine in the absence and presence of the protein and detecting the AC current response using phase-sensitive lock-in techniques. The conductances of individual alphaHL channels and OmpF porins were measured in symmetric KCl solutions containing between 5 and 1000 mM KCl. The AC and DC conductances of each protein were in agreement for all solution conditions, demonstrating the reliability of the AC method in single-channel recordings. Linear plots of conductance versus bulk KCl concentration for both proteins extrapolate to significant nonzero conductances (0.150 +/- 0.050 nS and 0.028 +/- 0.008 nS for OmpF and alphaHL, respectively) at infinite KCl dilution. The infinite dilution conductances are ascribed to mobile counterions of the ionizable residues within the protein lumens. A method of analyzing the plots of conductance vs KCl concentration is introduced that allows the determination of the concentration of mobile counterions associated with ionizable groups without knowledge of either the protein geometry or the ion mobilities. At neutral pH, an equivalent of 3 mobile counterions (K+ or Cl-) is estimated to contribute to the conductivity of the alphaHL channel.