Updating cut-off values of severity scoring systems for community-acquired pneumonia to orchestrate more predictive accuracy.

Background: The assessment of severity is crucial in the management of community-acquired pneumonia (CAP). It remains unknown whether updating cut-off values of severity scoring systems orchestrate improvement in predictive accuracy.Methods: 3,212 patients with CAP were recruited to two observational prospective cohort studies. Three bettered scoring systems were derived from the corresponding well-established and extensively used pneumonia-specific severity scoring systems, i.e. pneumonia severity index, minor criteria and CURB-65 (confusion, urea >7 mmol/L, respiratory rate ≥30/min, low blood pressure, and age ≥65 years) score, with the updating cut-off values for tachypnea and low blood pressure. Cronbach α was employed to determine construct validity. Discrimination was valued by calculating the area under the receiver operating characteristic curve (AUROC) and net reclassification improvement (NRI).Results: Respiratory rate ≥22/min and systolic blood pressure ≤100 mm Hg were performed better than respiratory rate ≥30/min and hypotension for predicting mortality in the derivation cohort, respectively (AUROC, 0.823 vs 0.519, 0.688 vs 0.622; NRI, 0.61, 0.13). Bettered scoring systems orchestrated higher convergences, indicated by greater Cronbach α and more decrease in Cronbach α if the updating cut-off values were deleted. The six scoring systems agreed well with one another. Bettered- pneumonia severity index, minor criteria and CURB-65 score showed higher associations with severity and mortality rates and demonstrated greater predictive accuracies for mortality compared with the corresponding original systems (AUROC, 0.939 vs 0.883, 0.909 vs 0.871, 0.913 vs 0.859; NRI, 0.113, 0.076, 0.108; respectively). The validation cohort confirmed a similar pattern.Conclusions: Updating cut-off values of severity scoring systems for CAP orchestrate improvement in predictive accuracy, suggesting that it may facilitate the rationalization of clinical triage decision-making and further reduce mortality. The current studies provide the first known prospective evidence of potential benefit of the updating cut-off values of severity scoring systems for CAP in predictive accuracy.Key messagesUpdating cut-off values were performed better for predicting mortality.Bettered scoring systems orchestrated higher convergences.Bettered scoring systems demonstrated greater predictive accuracies for mortality.

Cold-inducible RNA-binding protein might determine the severity and the presences of major/minor criteria for severe community-acquired pneumonia and best predicted mortality.

BACKGROUND: Severity of community-acquired pneumonia (CAP) depends on microbial pathogenicity, load and virulence, and immune responses. The Infectious Disease Society of America and the American Thoracic Society (IDSA/ATS) minor criteria responsible for clinical triage of patients with CAP are of unequal weight in predicting mortality. It is unclear whether the IDSA/ATS major/minor criteria might be strongly and positively associated with the immune responses. It is warranted to explore this intriguing hypothesis. METHODS: A prospective cohort study of 404 CAP patients was performed. Cold-inducible RNA-binding protein (CIRP) levels were measured using a sandwich-based enzyme-linked immunosorbent assay. The receiver operating characteristic curves were created and the areas under the curves were calculated to illustrate and compare the accuracy of the indices. RESULTS: Severe CAP patients meeting the major criteria had the highest plasma concentrations of CIRP. The more the number of most predictive minor criteria strongly associated to mortality, i.e. arterial oxygen pressure/fraction inspired oxygen ≤ 250 mmHg, confusion, and uremia, present, the higher the CIRP level. Interestingly, the patients with non-severe CAP meeting the most predictive minor criteria demonstrated unexpectedly higher CIRP level compared with the patients with severe CAP not fulfilling the criteria. Procalcitonin (PCT), interleukin-6 (IL-6), C-reactive protein (CRP), sequential organ failure assessment (SOFA) and pneumonia severity index (PSI) scores, and mortality confirmed similar intriguing patterns. CIRP was strongly linked to PCT, IL-6, CRP, minor criteria, SOFA and PSI scores, and mortality (increased odds ratio 3.433). The pattern of sensitivity, specificity, positive predictive value, and Youden's index of CIRP ≥ 3.50 ng/mL for predicting mortality was the optimal. The area under the receiver operating characteristic curve of CIRP was the highest among the indices. CONCLUSIONS: CIRP levels were strongly correlated with the IDSA/ATS major/minor criteria. CIRP might determine the severity and the presences of major/minor criteria and best predicted mortality, and a CIRP of ≥ 3.50 ng/mL might be more valuable cut-off value for severe CAP, suggesting that CIRP might be a novel and intriguing biomarker for pneumonia to monitor host response and predict mortality, which might have implications for more accurate clinical triage decisions.

P-STAT3 and IL-17 in tumor tissues enhances the prognostic value of CEA and CA125 in patients with lung adenocarcinoma.

AIM: The present study aimed to examine the capability of p- signal transducer and activator of transcription (STAT)3 and interleukin-17 (IL-17), along with two known tumor markers carcinoembryonic antigen (CEA) and carbohydrate antigen 125 (CA125), for disease prognosis. Moreover, the associations among biomarkers and clinicopathological parameters were evaluated to uncover the potential mechanisms responsible for their correlations with lung adenocarcinoma (LAD) prognosis. METHODS: Five LAD-related parameters were used in the study: CEA, CA125, STAT3, p-STAT3, and IL-17. Spearman and chi-square correlation tests were used to explore the relationships between some clinicopathological variables and parameter expression levels and the associations among these five parameters. RESULTS: The disease-specific survival decreased with the positive expression of CEA, CA125, p-STAT3, and IL-17, with no significant difference in the expression level of STAT3. Combinations of p-STAT3 and IL-17, CEA and p-STAT3, CEA and IL-17, CA125 and p-STAT3, and CA125 and IL-17 had higher predictive values in LAD prognosis. The correlation analyses indicated the synergic activities of STAT3, p-STAT3, and IL-17 and the coordinated expression of CEA, CA125, p-STAT3, and IL-17. The tumor-node-metastasis (TNM) stage significantly correlated with the levels of CA125 and p-STAT3. CONCLUSIONS: Elevated levels of CEA, CA125, p-STAT3, and IL-17 alone and/or combinations of p-STAT3 and IL-17, CEA and p-STAT3, CEA and IL-17, CA125 and p-STAT3, and CA125 and IL-17 were recommended as the prognostic predictors of unfavorable clinical outcomes in patients with postoperative LAD. Also, p-STAT3 and IL-17 combined with CA125 and CEA helped in predicting the overall survival of patients with LAD and informing the TNM stage.

Correction to: Scored minor criteria for severe community-acquired pneumonia predicted better.

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Scored minor criteria for severe community-acquired pneumonia predicted better.

BACKGROUND: Infectious Disease Society of America/American Thoracic Society (IDSA/ATS) minor criteria for severe community-acquired pneumonia (CAP) are of unequal weight in predicting mortality, but the major problem associated with IDSA/ATS minor criteria might be a lack of consideration of weight in prediction in clinical practice. Would awarding different points to the presences of the minor criteria improve the accuracy of the scoring system? It is warranted to explore this intriguing hypothesis. METHODS: A total of 1230 CAP patients were recruited to a retrospective cohort study. This was tested against a prospective two-center cohort of 1749 adults with CAP. 2 points were assigned for the presence of PaO2/FiO2 ≤ 250 mmHg, confusion, or uremia on admission and 1 point for each of the others. RESULTS: The mortality rates, and sequential organ failure assessment (SOFA) and pneumonia severity index (PSI) scores increased significantly with the numbers of IDSA/ATS minor criteria present and minor criteria scores. The correlations of the minor criteria scores with the mortality rates were higher than those of the numbers of IDSA/ATS minor criteria present. As were the correlations of the minor criteria scores with SOFA and PSI scores, compared with the numbers of IDSA/ATS minor criteria present. The pattern of sensitivity, specificity, positive predictive value, and Youden's index of scored minor criteria of ≥2 scores or the presence of 2 or more IDSA/ATS minor criteria for prediction of mortality was the best in the retrospective cohort, and the former was better than the latter. The validation cohort confirmed a similar pattern. The area under the receiver operating characteristic curve of scored minor criteria was higher than that of IDSA/ATS minor criteria in the retrospective cohort, implying higher accuracy of scored version for predicting mortality. The validation cohort confirmed a similar paradigm. CONCLUSIONS: Scored minor criteria orchestrated improvements in predicting mortality and severity in patients with CAP, and scored minor criteria of ≥2 scores or the presence of 2 or more IDSA/ATS minor criteria might be more valuable cut-off value for severe CAP, which might have implications for more accurate clinical triage decisions.

Priority for Treatment and Intensive Care of Patients With Non-Severe Community-Acquired Pneumonia.

BACKGROUND: The Infectious Disease Society of America/the American Thoracic Society (IDSA/ATS) minor criteria for severe community-acquired pneumonia (CAP) are of unequal weight in predicting mortality. It is unclear whether the patients with non-severe CAP meeting the minor criteria most strongly associated to mortality should have the priority for treatment and intensive care. It is warranted to explore this intriguing hypothesis. METHODS: A retrospective cohort study of 1230 patients with CAP was performed. This was tested against a prospective 2-center cohort of 1749 adults with CAP. RESULTS: The patients with CAP fulfilling the predictive findings most strongly associated to mortality, i.e. PaO2/FiO2 ≤ 250 mm Hg, confusion, and uremia, showed higher mortality rates than those not fulfilling the predictive findings in subgroup analyses of the retrospective cohort. The more the number of predictive findings present, the higher the mortality rates. The prospective cohort confirmed a similar pattern. Interestingly, the patients with non-severe CAP meeting the predictive findings demonstrated unexpectedly higher mortality rates compared with the patients with severe CAP not meeting the predictive findings in the prospective cohort (P = 0.003), although there only existed death of an uptrend in the retrospective cohort. Two similar and intriguing paradigms about sequential organ failure assessment (SOFA) scores and pneumonia severity index (PSI) scores were confirmed in the 2 cohorts. CONCLUSIONS: The patients with non-severe CAP fulfilling the predictive findings most strongly associated to mortality demonstrated higher SOFA and PSI scores and mortality rates, and might have the priority for treatment and intensive care.

Modified IDSA/ATS Minor Criteria for Severe Community-Acquired Pneumonia Best Predicted Mortality.

It is not clear whether the IDSA/ATS minor criteria for severe community-acquired pneumonia (CAP) could be simplified or even be modified to orchestrate improvements in predicting mortality.A retrospective cohort study of 1230 CAP patients was performed to simplify and to modify the scoring system by excluding 4 noncontributory or infrequent variables (leukopenia, hypothermia, hypotension, and thrombocytopenia) and by excluding these variables and then adding age ≥65 years, respectively. The simplification and modification were tested against a prospective 2-center validation cohort of 1409 adults with CAP.The increasing numbers of IDSA/ATS, simplified, and modified minor criteria present in the retrospective cohort were positively associated with the mortality, showing significant increased odds ratios for mortality of 2.711, 4.095, and 3.755, respectively. The validation cohort confirmed a similar pattern. The sensitivity, specificity, positive predictive value, and Youden index of modified minor criteria for mortality prediction were the best pattern in the retrospective cohort. High values of corresponding indices were confirmed in the validation cohort. The highest accuracy of the modified version for predicting mortality in the retrospective cohort was illustrated by the highest area under the receiver operating characteristic curve of 0.925 (descending order: modified, simplified, and IDSA/ATS minor criteria). The validation cohort confirmed a similar paradigm.The IDSA/ATS minor criteria could be simplified to 5 variables and then be modified to orchestrate improvements in predicting mortality in CAP patients. The modified version best predicted mortality. These were more suitable for clinic and emergency department.

CUR-65 Score for Community-Acquired Pneumonia Predicted Mortality Better Than CURB-65 Score in Low-Mortality Rate Settings.

BACKGROUND: It is not clear whether low-blood pressure criterion could be removed from CURB-65 (confusion, urea >7 mmol/L, respiratory rate ≥30/min, low blood pressure and age ≥65 years) score to orchestrate an improvement in identifying patients with community-acquired pneumonia (CAP) in low-mortality rate settings. METHODS: A retrospective cohort study of 1,230 CAP patients was performed to simplify the CURB-65 scoring system by excluding low-blood pressure variable. The simplification was validated in a prospective 2-center cohort of 1,409 adults with CAP. RESULTS: The hospital mortalities were 1.3% and 3.8% in the retrospective and prospective cohorts, respectively. The mortality rates in the 2 cohorts increased directly with the increasing scores, showing significant increased odds ratios for mortality. The pattern of sensitivity, specificity, positive predictive value and Youden's index of a CUR-65 (Confusion, Urea >7 mmol/L, Respiratory rate ≥30/min and age ≥65 years) score of ≥2 for prediction of mortality was better than that of a CURB-65 score of ≥3 in the retrospective cohort. Higher values of corresponding indices were confirmed in the validation cohort. The higher accuracy of CUR-65 score for predicting mortality was illustrated by the area under the receiver operating characteristic curve of 0.937, compared with 0.915 for CURB-65 score in the retrospective cohort (P = 0.0073). The validation cohort confirmed a similar paradigm (0.953 versus 0.907, P = 0.0002). CONCLUSIONS: CURB-65 score could be simplified by removing low blood pressure to orchestrate an improvement in predicting mortality in CAP patients who have a low risk of death. A CUR-65 score of ≥2 might be a more valuable cutoff value for severe CAP.

Mortality among severe community-acquired pneumonia patients depends on combinations of 2007 IDSA/ATS minor criteria.

OBJECTIVES: The individual 2007 Infectious Disease Society of America (IDSA)/American Thoracic Society (ATS) minor criteria for severe community-acquired pneumonia (CAP) are of unequal weight in predicting mortality. It is not clear whether the combinations of predictive findings might imply diverse severities or different mortalities. METHODS: A prospective two centre cohort study was performed of 385 severe CAP patients fulfilling three or more IDSA/ATS minor criteria amongst 1430 patients. RESULTS: Hospital mortality rose sharply from 5.7%, 9.9%, and 16.5%, respectively, for patients with none of three predictive findings most strongly associated to mortality (PaO2/FiO2 ≤ 250mm Hg, confusion and uraemia), one of those, and two of those to 38.6% for patients with all those (p<0.001). The number of three predictive findings present had a significantly increased odds ratio for mortality of 2.796 (p<0.001), and had the degree of positive association with sequential organ failure assessment scores at 72hours, incurring significantly longer hospital stay and higher costs. CONCLUSIONS: Different combinations of 2007 IDSA/ATS minor criteria for severe CAP were associated to diverse severities and different mortalities. The combination of PaO2/FiO2 ≤ 250mm Hg, confusion and uraemia predicted more severity and higher mortality compared with others.

Associations of radiological features in Mycoplasma pneumoniae pneumonia.

INTRODUCTION: The associations of radiological features with clinical and laboratory findings in Mycoplasma pneumoniae infection are poorly understood. The purpose of this study was to assess the associations. MATERIAL AND METHODS: A retrospective cohort study of 1230 patients with community-acquired pneumonia was carried out between January 2005 and December 2009. The diagnosis of M. pneumoniae infection was made using the indirect microparticle agglutinin assay and enzyme-linked immunosorbent assay. RESULTS: Females were more susceptible to M. pneumoniae infection. Ground-glass opacification on radiographs was positively associated with M. pneumoniae-IgM titres (rank correlation coefficient (r s) = 0.141, p = 0.006). The left upper lobe was more susceptible to infection with M. pneumoniae compared with other pathogens. More increases in the risk of multilobar opacities were found among older or male patients with M. pneumoniae pneumonia (odds ratio, 1.065, 3.279; 95% confidence interval, 1.041-1.089, 1.812-5.934; p < 0.001, p < 0.001; respectively). Patients with M. pneumoniae pneumonia showing multilobar opacities or consolidation had a significantly longer hospital length of stay (r s = 0.111, r s = 0.275; p = 0.033, p < 0.001; respectively), incurring significantly higher costs (r s = 0.119, r s = 0.200; p = 0.022, p < 0.001; respectively). CONCLUSIONS: Our study highlighted female susceptibility to M. pneumoniae pneumonia and the association of ground-glass opacification with higher M. pneumoniae-IgM titres. The left upper lobe might be more susceptible to M. pneumoniae infection. Older or male patients with M. pneumoniae pneumonia were more likely to show multilobar opacities. Multilobar opacities and consolidation were positively associated with hospital length of stay and costs.

Weight of the CURB-65 criteria for community-acquired pneumonia in a very low-mortality-rate setting.

OBJECTIVE: The CURB-65 score is a simple well validated tool for the assessment of severity in community-acquired pneumonia (CAP). The weight of each criterion in very low-mortality-rate settings is unclear. The purpose of this study was to determine the weight in such setting. METHODS: This study retrospectively reviewed 1,230 adult patients admitted for CAP from 2005 to 2009. RESULTS: The 30-day mortality rose sharply from 0%, 1.0%, 8.2% and 16.7%, respectively, for patients with CURB-65 scores of 0, 1, 2 and 3 to 100.0% for patients with the scores of 4 (x(2) = 219.494, p<0.001). Confusion had the strongest association with mortality (odds ratio, 22.148). The presence of low blood pressure was not associated with mortality. Confusion, urea >7 mmol.L(-1) and age ≥ 65 yrs showed independent relationships with mortality (Odds ratio, 11.537, 5.988 and 10.462; respectively). Urea >7 mmol.L(-1) was most strongly associated with the sequential organ failure assessment (SOFA) scores [rank correlation coefficient (r(s)), 0.352]. Confusion had the closest relationship with hospital length of stay (r(s), 0.114). Age ≥ 65 yrs had the strongest association with costs (r(s), 0.223). Conclusion The individual CURB-65 criteria were of unequal weight for predicting the 30-day mortality, SOFA scores, hospital length of stay and costs in a very low-mortality-rate setting, and a low blood pressure was not associated with mortality.

Prognostic role of Twist, Slug, and Foxc2 expression in stage I non-small-cell lung cancer after curative resection.

UNLABELLED: By using immunohistochemistry in tissue microarrays of 137 cases, we evaluated the prognostic power of a 3-marker epithelial-mesenchymal transition­related model in patients with stage I non-small-cell lung cancer who underwent radical surgical resection. The Twist/Slug/Foxc2 coexpression model accurately prognosticated these patients and may be helpful in refining current treatment strategy for stage I non-small-cell lung cancer. BACKGROUND: Lung cancer is the leading cause of cancer-related death in the world. Only about 60% of patients with stage I non-small-cell lung cancer (NSCLC) can be cured by surgery alone. Current clinical and molecular markers are inadequate prognosticators. We developed a 3-marker model that closely approximates survival probability of patients with stage I NSCLC. METHODS: Expression of Twist, Slug, and Foxc2 was assessed by immunohistochemistry in tissue microarrays that contained paired tumor and peritumoral lung tissue from 137 patients who underwent surgical resection for stage I NSCLC. The prognostic value of Twist, Slug, and Foxc2, and the cumulative effects of the 3 markers on survival were evaluated. RESULTS: Increased expression of Twist, Slug, and Foxc2 was observed in 38.0%, 18.2%, and 27.7% of primary tumors, respectively. Overexpression of Twist, Slug, and Foxc2 in stage I NSCLC was associated with a worse overall survival (P = .001, P = .002, P < .001, respectively) and correlated with a shorter recurrence-free survival (P < .001, P = .001, P < .001 respectively). The cumulative influence of these markers on outcome was analyzed; a combination of more than 2 positive markers was an independent predictor of recurrence-free and overall survival (P = .002 and P = .009, respectively). CONCLUSIONS: The Twist/Slug/Foxc2 model is useful in predicting survival of stage I NSCLC and may be helpful in refining current treatment strategy.

Weight of the IDSA/ATS minor criteria for severe community-acquired pneumonia.

BACKGROUND: The 2007 Infectious Disease Society of America (IDSA)/American Thoracic Society (ATS) guidelines defined severe community-acquired pneumonia (CAP) when patients fulfilled three out of nine minor criteria. Whether each of the criteria is of equal weight is not clear. The purpose of this study was to determine the weight of the minor criteria. METHODS: 1230 adult patients admitted to our hospital from 2005 to 2009 for CAP were reviewed retrospectively. RESULTS: Hospital mortality rose sharply from 0.3%, 1.0% and 3.3%, respectively, for patients with none, one and two minor criteria to 10.5% for patients with three minor criteria. Arterial oxygen pressure/fraction inspired oxygen (PaO(2)/FiO(2)) ≤ 250 mm Hg, confusion, and uremia had the strongest association with mortality (Odds ratio, 22.162, 22.148, 16.343; respectively). Leukopenia, hypothermia, and hypotension were not associated with mortality. Confusion and uremia showed independent relationships with mortality (Odds ratio, 9.296, 8.493; respectively). Sequential organ failure assessment (SOFA) scores and costs increased significantly with the number of minor criteria present. Uremia and PaO(2)/FiO(2) ≤ 250 mm Hg were most strongly associated with SOFA scores [rank correlation coefficient (r(s)), 0.352, 0.336; respectively]. PaO(2)/FiO(2) ≤ 250 mm Hg and confusion were in closest relation to hospital length of stay (LOS) (r(s), 0.114, 0.114; respectively). PaO(2)/FiO(2) ≤ 250 mm Hg and multilobar infiltrates were most strongly associated with costs (r(s), 0.257, 0.196; respectively). CONCLUSIONS: The individual 2007 IDSA/ATS minor criteria for severe CAP were of unequal weight in predicting hospital mortality, SOFA scores, hospital LOS, and costs.

[RAPD and SCAR molecular markers linked to the sexuality of cycads (Cycas tanqingii D. Y. Wang)].

The random amplified polymorphic DNA (RAPD) technique was used to amplify DNA fragment, aiming at finding markers linked to the sex trait in Cycas tanqingii D. Y. Wang. A total number of 160 random primers were screened in the RAPD-PCR and more than 2500 RAPD fragments were generated from the male or the female plants. One fragment of about 500 bp was amplified steadily and repeatedly by the S0465 (CCCCGGTAAC) primer only from female plants but not male plants. The RAPD marker was then converted into female-linked dominant SCAR (Sequence Characterized Amplified Regions) marker named STQC-S465-483. The development of this sex-linked SCAR marker provides a possibility of identifying the sex of Cycas tanqingii before sexual maturation, which is very important to in situ or ex situ conservation.

"Kiss-and-run" exocytosis in astrocytes.

Neurons and glia are the principal cellular components of the nervous system. Although the glia are 10 times more numerous than neurons, until recently they were thought to be passive cells that monitor and support the active neurons by taking up used neurotransmitters from the synapses. In the past few years, this concept has been challenged by the findings that Ca(2+) waves spread from one astrocyte to another via Ca(2+)-and SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-dependent gliotransmitter release in pure cultures of astrocytes, raising the possibility that glia are not so passive as previously thought. This hypothesis was further advanced by two recent reports, which demonstrated that astrocytes release glutamate via vesicular exocytosis in response to stimuli. The kinetics of single vesicle exocytosis is distinct from its neural equivalent, because in response to physiological stimulation, gliotransmitter release is exclusively in the mode of "kiss and run." These advances were made possible by newly available techniques for single vesicle recordings, which will also be briefly reviewed here.

Activation of GPCRs modulates quantal size in chromaffin cells through G(betagamma) and PKC.

Exocytosis proceeds by either full fusion or 'kiss-and-run' between vesicle and plasma membrane. Switching between these two modes permits the cell to regulate the kinetics and amount of secretion. Here we show that ATP receptor activation reduces secretion downstream from cytosolic Ca2+ elevation in rat adrenal chromaffin cells. This reduction is mediated by activation of a pertussis toxin-sensitive G(i/o) protein, leading to activation of G(betagamma) subunits, which promote the 'kiss-and-run' mode by reducing the total open time of the fusion pore during a vesicle fusion event. Furthermore, parallel activation of the muscarinic acetylcholine receptor removes the inhibitory effects of ATP on secretion. This is mediated by a G(q) pathway through protein kinase C activation. The inhibitory effects of ATP and its reversal by protein kinase C activation are also shared by opioids and somatostatin. Thus, a variety of G protein pathways exist to modulate Ca2+-evoked secretion at specific steps in fusion pore formation.

Na+ channel inactivation: a comparative study between pancreatic islet beta-cells and adrenal chromaffin cells in rat.

A comparative study was carried out on the inactivation of Na+ channels in two types of endocrine cells in rats, beta-cells and adrenal chromaffin cells (ACCs), using patch-clamp techniques. The beta-cells were very sensitive to hyperpolarization; the Na+ currents increased ninefold when the holding potential was shifted from -70 mV to -120 mV. ACCs were not sensitive to hyperpolarization. The half-inactivation voltages were -90 mV (rat beta-cells) and -62 mV (ACCs). The time constant for recovery from inactivation at -70 mV was 10.5 times slower in beta-cells (60 ms) than in ACCs (5.7 ms). The rate of Na+-channel inactivation at physiological resting potential was more than three times slower in beta-cells than in ACCs. Na+ influx through Na+ channels had no effect on the secretory machinery in rat beta-cells. However, these 'silent Na+ channels' could contribute to the generation of action potentials in some conditions, such as when the cell is hyperpolarized. It is concluded that the fractional availability of Na+ channels in beta-cells at a holding potential of -70 mV is about 15 % of that in ACCs. This value in rat beta-cells is larger than that observed in mouse (0 %), but is smaller than those observed in human or dog (90 %).

A novel conotoxin from Conus betulinus, kappa-BtX, unique in cysteine pattern and in function as a specific BK channel modulator.

A novel conotoxin, kappa-conotoxin (kappa-BtX), has been purified and characterized from the venom of a worm-hunting cone snail, Conus betulinus. The toxin, with four disulfide bonds, shares no sequence homology with any other conotoxins. Based on a partial amino acid sequence, its cDNA was cloned and sequenced. The deduced sequence consists of a 26-residue putative signal peptide, a 31-residue mature toxin, and a 13-residue extra peptide at the C terminus. The extra peptide is cleaved off by proteinase post-processing. All three Glu residues are gamma-carboxylated, one of the two Pro residues is hydroxylated at position 27, and its C-terminal residue is Pro-amidated. The monoisotopic mass of the toxin is 3569.0 Da. Electrophysiological experiments show that: 1) among voltage-gated channels, kappa-BtX is a specific modulator of K(+) channels; 2) among the K channels, kappa-BtX specifically up-modulates the Ca(2+)- and voltage-sensitive BK channels (252 +/- 47%); 3) its EC(50) is 0.7 nm with a single binding site (Hill = 0.88); 4) the time constant of wash-out is 8.3 s; and 5) kappa-BtX has no effect on single channel conductance, but increases the open probability of BK channels. It is concluded that kappa-BtX is a novel specific biotoxin against BK channels.