Human pulmonary vascular and venous compliances are reduced before and during left-sided heart failure

1995 ◽  
Vol 78 (1) ◽  
pp. 323-333 ◽  
Author(s):  
S. Hirakawa ◽  
T. Suzuki ◽  
K. Gotoh ◽  
H. Ito ◽  
T. Tanaka ◽  
...  
Keyword(s):  
Heart Failure ◽  
Heart Association ◽  
Class Ii ◽  
Venous System ◽  
Class I ◽  
Ratio Method ◽  
Class Iii ◽  
Venous Compliance ◽  
Venous Flow ◽  
Pulmonary Capillary

Human pulmonary vascular and venous compliances were measured in 41 patients with or without left-sided heart failure. Two methods were used. Method 1 was based on analysis of pulmonary capillary wedge (PCW) pressure tracings according to Cv,PCW = (SF/100)(0.075PCW + 0.90)SV/[(v - d)PCW + 1], where Cv,PCW is compliance of pulmonary venous system, SF is systolic fraction of pulmonary venous flow [related to pulmonary capillary wedge pressure (PCW) as SF = 82 – 2.01PCW], (v - d)PCW is pulse pressure in PCW position, and SV is stroke volume. The (0.075PCW + 0.90) term equals k “, i.e., systolic run-off ratio. Method 2 was used to measure to pulmonary vascular volume-pressure (V-P) relationship and pulmonary vascular compliance (Cvasc) and is based on measurement of pulmonary blood volume (PBV) and its increase with passive elevation of the legs to calculate Cvasc. Assuming the proportion of blood entering pulmonary venous system (in increase of PBV) during passive leg elevation to be 0.8, pulmonary venous compliance (Cv,PBV) was calculated as Cv,PBV = 0.8Cvasc. Cv,PCW correlated fairly closely with Cv,PBV (r = 0.81, coefficient of variation = 31%). This fair agreement between two independent methods suggests strongly that both methods may be valid, although other interpretations are possible. Cv,PCW, Cvasc, and Cv,PBV decreased going from New York Heart Association class I to classes II and III. When PBV was plotted vs. PCW, average V-P line for class II patients was flatter and shifted downward to the right compared with that for class I. This suggests pulmonary vasoconstriction as well as other factors. Average V-P line for class III patients is flatter but not displaced compared with that for class II. Another previously reported series of 50 patients, most of whom had ischemic heart disease, are included in this study.

Outpatient Costs of Medications for Patients with Chronic Heart Failure

2002 ◽  
Vol 11 (5) ◽  
pp. 474-478 ◽  
Author(s):  
Leslie C. Hussey ◽  
Sonya Hardin ◽  
Christopher Blanchette
Keyword(s):  
Heart Failure ◽  
New York ◽  
Chronic Heart Failure ◽  
Web Sites ◽  
Heart Association ◽  
Class Ii ◽  
Class I ◽  
Class Iii ◽  
Ability To Pay ◽  
New York Heart Association

• Background The outpatient costs of medications prescribed for chronic heart failure are high and are often borne by individual patients. Lack of financial resources may force noncompliance with use of medications. • Objective To compare the outpatient costs of medications for patients with different New York Heart Association classifications of chronic heart failure. • Methods The charts of 138 patients with chronic heart failure were reviewed retrospectively. Outpatient costs of medications were obtained from the Web sites of commercial pharmacies. Medications were classified by type according to the system of the American Heart Association. A mean cost for each classification of medication was used for analysis. • Results The overall mean monthly cost of medications for chronic heart failure was $438. Patients with class II and class III chronic heart failure had the highest costs: $541 and $514, respectively. Analysis of variance indicated that the differences in monthly costs of medications between the patients with the 4 stages of chronic heart failure were significant (F = 4.86, P = .003). A post hoc Scheffé test revealed significant differences in costs between patients with class I and patients with class II heart failure (P=.02) and between patients with class I and those with class III heart failure (P=.02). • Conclusions The outpatient costs of medications for chronic heart failure are significant. Ability to pay for prescribed medications must be determined. Healthcare professionals must maintain an awareness of the costs of medications and patients’ ability to pay.

scholarly journals Experience of post-infarction left ventricular aneurysm reconstruction with on-pump beating heart technique

2019 ◽  
Vol 100 (3) ◽  
pp. 500-504
Author(s):  
D G Tarasov ◽  
I I Chernov ◽  
A V Molochkov ◽  
A V Pavlov
Keyword(s):  
Left Ventricle ◽  
Heart Association ◽  
Class Ii ◽  
Left Ventricular ◽  
Beating Heart ◽  
Class I ◽  
Left Ventricular Aneurysm ◽  
Class Iii ◽  
Left Ventricular Reconstruction ◽  
Class Iv

Aim. To evaluate the results of surgical treatment of post-infarction left ventricular aneurysms with on-pump beating heart technique. Methods. In our center from April, 2009 to January, 2014 169 patients had reconstruction of the left ventricle with on-pump beating heart technique. Among the patients 159 were males (94.1%) and 10 of them were females (5.9%), average age 53.8±8.9 years (39 to 72 years). Angina pectoris class I (according to the classification of Canadian Heart Association) was established in 7 (4.1%) patients, class II - in 49 (29.0%), class III - in 107 (63.3%), class IV - in 4 (2.4%), unstable angina in 2 (1.2%) patients. Chronic heart failure class I (according to New York Heart association functional classification) was diagnosed in 5 (3.0%) patients, class II in 37 (21.9%), class III in 124 (73.4%), class IV in 3 (1.8%) patients. Average ejection fraction of the left ventricle was 38.6±7.9% (25 to 67%). Mitral valve insufficiency stage 2-3 was revealed in 23 (13.6%) patients. Results. Endoventriculoplasty of the left ventricle by Dor's technique was performed in 49 (29.0%) patients, auto-septoplasty of the left ventricle - 59 (34.9%) patients, linear repair in 40 (23.7%) patients. Combined surgical interventions were performed in 21 (12.4%) patients. In-hospital lethality was 2.4% (n=4). Conclusion. Left ventricular reconstruction with on-pump beating heart technique without cardioplegic arest is effective and safe; the method allows performing remodelling of the left ventricle and reaching the target volume parameters.

scholarly journals Outcome of Albumin Infusion in Heart Failure Patients

2019 ◽  
Vol 15 (2) ◽  
pp. 47-53
Author(s):  
Ashaduzzaman Talukder ◽  
Mohamed Mausool Siraj ◽  
Md Noornabi Khondokar ◽  
SM Ahsan Habib ◽  
Md Abu Salim ◽  
...  
Keyword(s):  
Heart Failure ◽  
Serum Albumin ◽  
Nyha Class ◽  
Class Ii ◽  
Class I ◽  
Class Iii ◽  
Albumin Infusion ◽  
Group A ◽  
Group B ◽  
Class Iv

Background: Heart Failure (HF) is a major public health burden worldwide. Approximately 5 million Americans, 0.4–2% of the general European population and over 23 million people worldwide are living with heart failure. Like few other chronic disease, low serum albumin is common in patients with heart failure (HF). However, very few studies evaluated the outcome of albumin infusion in different stages of HF. Therefore, the objective of this study is to assess the outcome of albumin infusion in heart failure patients. Methods: It was a cross-sectional study. A total of 50 cases of chronic heart failure with reduced ejection fraction and NYHA class III or IV with serum albumin level <2.5g/dl who were admitted in CCUwere selected by purposive sampling, from September 2017 to August 2018. 100ml of 20% albumin was infused and serum albumin was measured after 3 days. Then the patients were divided into two groups, Patients who failed to attain serum albumin of 3g/dl(Group A) or Patients who attained serum albumin of ≥3g/dl (Group B). Analysis and comparison for symptomatic improvement of heart failure by NHYA classification and LVEF was done at 10th day after infusion between group A and B. Result: Among the 50 patients, mean age of patients was 53.64 ± 13.44 years (age range: 26-84 years) with a male-female ratio of 3:2 (60%-male vs 40%- female). Majority patients were previously re-admitted at least two times (40%), 28% were re-admitted once, 16% were re-admitted three times and 4% were re-admitted for four times. Of all, 56% patients presented NYHA class IV and AHA stage D heart failure (56%) and 44% patients presented with NYHA class III and AHA stage C. At day 10 follow up following albumin infusion, overall frequency of following ten days of albumin therapy, in group B, 8 patients (72.7%) among Class III improved to Class I and 3 patients (27.3%) improved to class II. Also, 7 patients (50%), 5 patients (35.7%) and 2 patients (14.3%) among class IV improved to respectively class I, class II and class III. In group A, 3 patients (27.3%) among class III improve to class II and 8 patients (72.7%) remain in class III. Also, 2 patients (14.3%), 5 Patients (35.7%) and 7 patients (50%) among class IV improve to respectively class I, class II and class III. Moreover, statistically significant improvement was noted in ejection fraction of patents irrespective of initial class of heart failure (p<0.001) in group B patients compare to group A (p<0.09). Conclusion: In this study, the improvement of heart failure was more in patients who attained albumin level of ≥3g/dl.Therefore, in can be concluded that albumin infusion improves both subjective and objective improvement of patients with heart failure. University Heart Journal Vol. 15, No. 2, Jul 2019; 47-53

Serum metabolic characteristics and biomarkers of early-stage heart failure

2020 ◽  
Vol 14 (2) ◽  
pp. 119-130
Author(s):  
Siqi Guo ◽  
Jing Kong ◽  
Danya Zhou ◽  
Minchao Lai ◽  
Yirun Chen ◽  
...  
Keyword(s):  
Heart Failure ◽  
New York ◽  
Early Stage ◽  
Heart Association ◽  
Class Ii ◽  
Class I ◽  
Metabolic Characteristics ◽  
Diagnostic Potential ◽  
Association Class ◽  
New York Heart Association

Aim: We aimed to identify metabolic characteristics of early-stage heart failure (HF) and related biomarkers. Patients & methods: One hundred and forty-three patients with New York Heart Association class I–IV HF and 34 healthy controls were recruited. Serum metabolic characteristics of class I HF were analyzed and compared with those of class II–IV HF. Potential biomarkers of class I HF with normal N-terminal-pro-B-type natriuretic peptide (NT-proBNP) level were screened and validated in additional 72 subjects (46 class I patients and 26 controls). Results & conclusion: Eleven metabolites were found disturbed in class I HF, and five of which were also disturbed in class II–IV HF. Glutamine and tyrosine showed high value to identify class I HF with normal NT-proBNP level. The diagnostic potential of glutamine was partially confirmed in the validate set, holding a promise to detect early HF with normal NT-proBNP level.

scholarly journals Telemonitoring Versus Usual Care for Elderly Patients With Heart Failure Discharged From the Hospital in the United States: Cost-Effectiveness Analysis (Preprint)

2020 ◽  
Author(s):  
Xinchan Jiang ◽  
Jiaqi Yao ◽  
Joyce HS You
Keyword(s):  
Heart Failure ◽  
Sensitivity Analysis ◽  
Cost Effectiveness ◽  
Usual Care ◽  
Nyha Class ◽  
Cost Effective ◽  
Class Ii ◽  
Class I ◽  
Class Iii ◽  
Hospitalization Cost

BACKGROUND Telemonitoring-guided interventional management reduces the need for hospitalization and mortality of patients with chronic heart failure (CHF). OBJECTIVE This study aimed to analyze the cost-effectiveness of usual care with and without telemonitoring-guided management in patients with CHF discharged from the hospital, from the perspective of US health care providers. METHODS A lifelong Markov model was designed to estimate outcomes of (1) usual care alone for all postdischarge patients with CHF (New York Heart Association [NYHA] class I-IV), (2) usual care and telemonitoring for all postdischarge patients with CHF, (3) usual care for all postdischarge patients with CHF and telemonitoring for patients with NYHA class III to IV, and (4) usual care for all postdischarge patients with CHF plus telemonitoring for patients with NYHA class II to IV. Model inputs were derived from the literature and public data. Sensitivity analyses were conducted to assess the robustness of model. The primary outcomes were total direct medical cost, quality-adjusted life years (QALYs), and incremental cost-effectiveness ratio (ICER). RESULTS In the base case analysis, universal telemonitoring group gained the highest QALYs (6.2967 QALYs), followed by the telemonitoring for NYHA class II to IV group (6.2960 QALYs), the telemonitoring for NYHA class III to IV group (6.2450 QALYs), and the universal usual care group (6.1530 QALYs). ICERs of the telemonitoring for NYHA class III to IV group (US $35,393 per QALY) and the telemonitoring for NYHA class II to IV group (US $38,261 per QALY) were lower than the ICER of the universal telemonitoring group (US $100,458 per QALY). One-way sensitivity analysis identified five critical parameters: odds ratio of hospitalization for telemonitoring versus usual care, hazard ratio of all-cause mortality for telemonitoring versus usual care, CHF hospitalization cost and monthly outpatient costs for NYHA class I, and CHF hospitalization cost for NYHA class II. In probabilistic sensitivity analysis, probabilities of the universal telemonitoring, telemonitoring for NYHA class II to IV, telemonitoring for NYHA class III to IV, and universal usual care groups to be accepted as cost-effective at US $50,000 per QALY were 2.76%, 76.31%, 18.6%, and 2.33%, respectively. CONCLUSIONS Usual care for all discharged patients with CHF plus telemonitoring-guided management for NYHA class II to IV patients appears to be the preferred cost-effective strategy.

scholarly journals Telemonitoring Versus Usual Care for Elderly Patients With Heart Failure Discharged From the Hospital in the United States: Cost-Effectiveness Analysis

10.2196/17846 ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. e17846
Author(s):  
Xinchan Jiang ◽  
Jiaqi Yao ◽  
Joyce HS You
Keyword(s):  
Heart Failure ◽  
Sensitivity Analysis ◽  
Cost Effectiveness ◽  
Usual Care ◽  
Nyha Class ◽  
Cost Effective ◽  
Class Ii ◽  
Class I ◽  
Class Iii ◽  
Hospitalization Cost

Background Telemonitoring-guided interventional management reduces the need for hospitalization and mortality of patients with chronic heart failure (CHF). Objective This study aimed to analyze the cost-effectiveness of usual care with and without telemonitoring-guided management in patients with CHF discharged from the hospital, from the perspective of US health care providers. Methods A lifelong Markov model was designed to estimate outcomes of (1) usual care alone for all postdischarge patients with CHF (New York Heart Association [NYHA] class I-IV), (2) usual care and telemonitoring for all postdischarge patients with CHF, (3) usual care for all postdischarge patients with CHF and telemonitoring for patients with NYHA class III to IV, and (4) usual care for all postdischarge patients with CHF plus telemonitoring for patients with NYHA class II to IV. Model inputs were derived from the literature and public data. Sensitivity analyses were conducted to assess the robustness of model. The primary outcomes were total direct medical cost, quality-adjusted life years (QALYs), and incremental cost-effectiveness ratio (ICER). Results In the base case analysis, universal telemonitoring group gained the highest QALYs (6.2967 QALYs), followed by the telemonitoring for NYHA class II to IV group (6.2960 QALYs), the telemonitoring for NYHA class III to IV group (6.2450 QALYs), and the universal usual care group (6.1530 QALYs). ICERs of the telemonitoring for NYHA class III to IV group (US $35,393 per QALY) and the telemonitoring for NYHA class II to IV group (US $38,261 per QALY) were lower than the ICER of the universal telemonitoring group (US $100,458 per QALY). One-way sensitivity analysis identified five critical parameters: odds ratio of hospitalization for telemonitoring versus usual care, hazard ratio of all-cause mortality for telemonitoring versus usual care, CHF hospitalization cost and monthly outpatient costs for NYHA class I, and CHF hospitalization cost for NYHA class II. In probabilistic sensitivity analysis, probabilities of the universal telemonitoring, telemonitoring for NYHA class II to IV, telemonitoring for NYHA class III to IV, and universal usual care groups to be accepted as cost-effective at US $50,000 per QALY were 2.76%, 76.31%, 18.6%, and 2.33%, respectively. Conclusions Usual care for all discharged patients with CHF plus telemonitoring-guided management for NYHA class II to IV patients appears to be the preferred cost-effective strategy.

scholarly journals Environmental Cadmium Exposure and Dental Indices in Orthodontic Patients

Healthcare ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 413
Author(s):  
Hui-Ling Chen ◽  
Jason Chen-Chieh Fang ◽  
Chia-Jung Chang ◽  
Ti-Feng Wu ◽  
I-Kuan Wang ◽  
...  
Keyword(s):  
Cadmium Concentration ◽  
Class Ii ◽  
Cadmium Exposure ◽  
Class I ◽  
P Value ◽  
Tooth Decay ◽  
Class Iii ◽  
Orthodontic Patients ◽  
Urine Cadmium ◽  
The Mean

Background. Previous studies have shown that environmental cadmium exposure could disrupt salivary gland function and is associated with dental caries and reduced bone density. Therefore, this cross-sectional study attempted to determine whether tooth decay with tooth loss following cadmium exposure is associated with some dental or skeletal traits such as malocclusions, sagittal skeletal pattern, and tooth decay. Methods. Between August 2019 and June 2020, 60 orthodontic patients with no history of previous orthodontics, functional appliances, or surgical treatment were examined. The patients were stratified into two groups according to their urine cadmium concentrations: high (>1.06 µg/g creatinine, n = 28) or low (<1.06 µg/g creatinine, n = 32). Results. The patients were 25.07 ± 4.33 years old, and most were female (female/male: 51/9 or 85%). The skeletal relationship was mainly Class I (48.3%), followed by Class II (35.0%) and Class III (16.7%). Class I molar relationships were found in 46.7% of these patients, Class II molar relationships were found in 15%, and Class III molar relationships were found in 38.3%. The mean decayed, missing, and filled surface (DMFS) score was 8.05 ± 5.54, including 2.03 ± 3.11 for the decayed index, 0.58 ± 1.17 for the missing index, and 5.52 ± 3.92 for the filled index. The mean index of complexity outcome and need (ICON) score was 53.35 ± 9.01. The facial patterns of these patients were within the average low margin (26.65 ± 5.53 for Frankfort–mandibular plane angle (FMA)). There were no significant differences in the above-mentioned dental indices between patients with high urine cadmium concentrations and those with low urine cadmium concentrations. Patients were further stratified into low (<27, n = 34), average (27–34, n = 23), and high (>34, n = 3) FMA groups. There were no statistically significant differences in the urine cadmium concentration among the three groups. Nevertheless, a marginally significant p-value of 0.05 for urine cadmium concentration was noted between patients with low FMA and patients with high FMA. Conclusion. This analysis found no association between environmental cadmium exposure and dental indices in our orthodontic patients.

Revisiting heart failure assessment based on objective measures in NYHA functional classes I and II

Heart ◽  
2020 ◽  
pp. heartjnl-2020-317984
Author(s):  
Mariana Blacher ◽  
André Zimerman ◽  
Pedro H B Engster ◽  
Eduardo Grespan ◽  
Carisi A Polanczyk ◽  
...  
Keyword(s):  
Heart Failure ◽  
Nyha Class ◽  
Heart Association ◽  
Functional Class ◽  
Class I ◽  
Objective Measures ◽  
Functional Evaluation ◽  
Self Perception ◽  
Reduced Ejection Fraction ◽  
Nyha Classification

ObjectiveNew York Heart Association (NYHA) functional class plays a central role in heart failure (HF) assessment but might be unreliable in mild presentations. We compared objective measures of HF functional evaluation between patients classified as NYHA I and II in the Rede Brasileira de Estudos em Insuficiência Cardíaca (ReBIC)-1 Trial.MethodsThe ReBIC-1 Trial included outpatients with stable HF with reduced ejection fraction. All patients had simultaneous protocol-defined assessment of NYHA class, 6 min walk test (6MWT), N-terminal pro-brain natriuretic peptide (NT-proBNP) levels and patient’s self-perception of dyspnoea using a Visual Analogue Scale (VAS, range 0–100).ResultsOf 188 included patients with HF, 122 (65%) were classified as NYHA I and 66 (35%) as NYHA II at baseline. Although NYHA class I patients had lower dyspnoea VAS Scores (median 16 (IQR, 4–30) for class I vs 27.5 (11–49) for class II, p=0.001), overlap between classes was substantial (density overlap=60%). A similar profile was observed for NT-proBNP levels (620 pg/mL (248–1333) vs 778 (421–1737), p=0.015; overlap=78%) and for 6MWT distance (400 m (330–466) vs 351 m (286–408), p=0.028; overlap=64%). Among NYHA class I patients, 19%–34% had one marker of HF severity (VAS Score >30 points, 6MWT <300 m or NT-proBNP levels >1000 pg/mL) and 6%–10% had two of them. Temporal change in functional class was not accompanied by variation on dyspnoea VAS (p=0.14).ConclusionsMost patients classified as NYHA classes I and II had similar self-perception of their limitation, objective physical capabilities and levels of natriuretic peptides. These results suggest the NYHA classification poorly discriminates patients with mild HF.

scholarly journals Remote monitoring of chronic heart failure patients: invasive versus non-invasive tools for optimising patient management

2019 ◽  
Vol 28 (1) ◽  
pp. 3-13 ◽  
Author(s):  
J. F. Veenis ◽  
J. J. Brugts
Keyword(s):  
Heart Failure ◽  
New York ◽  
Chronic Heart Failure ◽  
Remote Monitoring ◽  
Heart Association ◽  
The United States ◽  
Pharmacological Therapy ◽  
Functional Class ◽  
Class Iii ◽  
Additional Tool

AbstractExacerbations of chronic heart failure (HF) with the necessity for hospitalisation impact hospital resources significantly. Despite all of the achievements in medical management and non-pharmacological therapy that improve the outcome in HF, new strategies are needed to prevent HF-related hospitalisations by keeping stable HF patients out of the hospital and focusing resources on unstable HF patients. Remote monitoring of these patients could provide the physicians with an additional tool to intervene adequately and promptly. Results of telemonitoring to date are inconsistent, especially those of telemonitoring with traditional non-haemodynamic parameters. Recently, the CardioMEMS device (Abbott Inc., Atlanta, GA, USA), an implantable haemodynamic remote monitoring sensor, has shown promising results in preventing HF-related hospitalisations in chronic HF patients hospitalised in the previous year and in New York Heart Association functional class III in the United States. This review provides an overview of the available evidence on remote monitoring in chronic HF patients and future perspectives for the efficacy and cost-effectiveness of these strategies.

scholarly journals A convenient method of preparation of high-activity urease from Canavalia ensiformis by covalent chromatography and an investigation of its thiol groups with 2,2'-dipyridyl disulphide as a thiol titrant and reactivity probe

1976 ◽  
Vol 159 (2) ◽  
pp. 245-257 ◽  
Author(s):  
R Norris ◽  
K Brocklehurst
Keyword(s):  
Convenient Method ◽  
Specific Activity ◽  
Class Ii ◽  
High Reactivity ◽  
Class I ◽  
Thiol Groups ◽  
Class Iii ◽  
Active Centre ◽  
Class Ib ◽  
Covalent Chromatography

1. A convenient method of preparation of jack-bean urease (EC3.5.1.5) involving covalent chromatography by thiol-disulphide interchange is described. 2. Urease thus prepared has specific activity comparable with the highest value yet reported (44.5 ± 1.47 kat/kg, Km = 3.32 ± 0.05 mM; kcat. = 2.15 × 104 ± 0.05 × 104s-1 at pH7.0 and 38°C). 3. Titration of the urease thiol groups with 2,2'-dipyridyl disulphide (2-Py-S-S-2-Py) and application of the method of Tsou Chen-Lu [(1962) Sci. Sin.11, 1535-1558] suggests that the urease molecule (assumed to have mol.wt. 483000 and ε280 = 2.84 × 105 litre·mol-1-cm-1) contains 24 inessential thiol groups of relatively high reactivity (class-I), six ‘essential’ thiol groups of low reactivity (class-II) and 54 buried thiol groups (class-III) which are exposed in 6M-guanidinium chloride. 4. The reaction of the class-I thiol groups with 2-Py-S-S-2-Py was studied in the pH range 6-11 at 25°C(I = 0.1 mol/l) by stopped-flow spectrophotometry, and the analogous reaction of the class-II thiol groups by conventional spectrophotometry. 5. The class-I thiol groups consist of at least two sub-classes whose reactions with 2-Py-S-S-2-Py are characterized by (a) pKa = 9.1, k = 1.56 × 104M-1·s-1 and (b) pKa = 8.1, k = 8.05 × 102M-1·s-1 respectively. The reaction of the class-II thiol groups is characterized by pKa = 9.15 and k = 1.60 × 102M-1·s-1. 6. At pH values 7-8 the class-I thiol groups consist of approx. 50% class-Ia groups and 50% class-Ib groups. The ratio class Ia/class Ib decreases as the pH is raised according to a pKa value ≥ approx. 9.5, and at high pH the class-I thiol groups consist of at most 25% class-Ia groups and at least 75% class-Ib groups. 7. The reactivity of the class-II thiol groups towards 2-Py-S-S-2-Py is insensitive to the nature of the group used to block the class-I thiols. 8. All the ‘essential’ thiol groups in urease appear to be eeactive only as uncomplicated thiolate ions. The implications of this for the active-centre chemistry of urease relative to that of the thiol proteinases are discussed.

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