High molecular weight kininogen inhibits thrombin-induced platelet aggregation and cleavage of aggregin by inhibiting binding of thrombin to platelets.

In this study we show that high molecular weight kininogen (HK) inhibited alpha-thrombin-induced aggregation of human platelets in a dose-dependent manner with complete inhibition occurring at plasma concentration (0.67 mumol/L) of HK. HK (0.67 mumol/L) also completely inhibited thrombin-induced cleavage of aggregin (Mr = 100 Kd), a surface membrane protein that mediates adenosine diphosphate (ADP)-induced shape change, aggregation, and fibrinogen binding. The inhibition of HK was specific for alpha- and gamma-thrombin-induced platelet aggregation, because HK did not inhibit platelet aggregation induced by ADP, collagen, calcium ionophore (A23187), phorbol myristate acetate (PMA), PMA + A23187, or 9,11-methano derivative of prostaglandin H2 (U46619). These effects were explained by the ability of HK, at physiologic concentration, to completely inhibit binding of 125I-alpha-thrombin to washed platelets. As a result of this action of HK, this plasma protein also completely inhibited thrombin-induced secretion of adenosine triphosphate, blocked intracellular rise in Ca2+ in platelets exposed to alpha- and gamma-thrombin, inhibited thrombin-induced platelet shape change, and blocked the ability of thrombin to antagonize the increase in intracellular cyclic adenosine monophosphate (cAMP) levels induced by iloprost. Because elevation of cAMP is known to inhibit binding of thrombin to platelets, we established that HK did not increase the intracellular concentration of platelet cAMP. Finally, HK did not inhibit enzymatic activity of thrombin. To study the role of HK in the plasma environment, we used gamma-thrombin to avoid fibrin formation by alpha-thrombin. Platelet aggregation induced by gamma-thrombin was also inhibited by HK in a dose-dependent manner. The EC50 (concentration to produce 50% of the maximum rate of aggregation) of gamma-thrombin for washed platelets was 7 nmol/L and increased to 102 nmol/L when platelets were suspended in normal human plasma. The EC50 for platelet aggregation induced by alpha-thrombin in plasma deficient in total kininogen was 40 nmol/L. When supplemented with HK at plasma concentration (0.67 mumol/L), the EC50 increased to 90 nmol/L, a value similar to that for normal human plasma. These results indicate that (1) HK inhibits thrombin-induced platelet aggregation and cleavage of aggregin by inhibiting binding of thrombin to platelets; (2) HK is a specific inhibitor of platelet aggregation induced by alpha- and gamma-thrombin; and (3) HK plays a role in modulating platelet aggregation stimulated by alpha-thrombin in plasma.     

Effectiveness of a combined exercise training and home-based walking programme on physical activity compared with standard medical care in moderate COPD: a randomised controlled trial

Objective

To estimate the effectiveness of a 10-week combined exercise training and home-based walking programme on daily physical activity (PA) compared with standard medical care in patients with moderate chronic obstructive pulmonary disease (COPD).

Health-related outcomes of critically ill patients with and without sepsis

Purpose

To determine differences in health-related quality of life (HRQoL), survival and healthcare resource use of critically ill adults with and without sepsis.

Methods

We conducted a primary propensity score matched analysis of patients with and without sepsis enrolled in a large multicentre clinical trial. Outcomes included HRQoL at 6 months, survival to 2 years, length of ICU and hospital admission and cost of ICU and hospital treatment to 2 years.

Results

We obtained linked data for 3442 (97.3%) of 3537 eligible patients and matched 806/905 (89.0%) patients with sepsis with 806/2537 (31.7%) without. After matching, there were no significant differences in the proportion of survivors with and without sepsis reporting problems with mobility (37.8% vs. 38.7%, p?=?0.86), self-care (24.7% vs. 26.0%, p?=?0.44), usual activities (44.5% vs. 46.8%, p?=?0.28), pain/discomfort (42.4% vs. 41.6%, p?=?0.54) and anxiety/depression (36.9% vs. 37.7%, p?=?0.68). There was no significant difference in survival at 2 years: 482/792 (60.9%) vs. 485/799 (60.7%) (HR 1.01, 95% CI 0.86–1.18, p?=?0.94). The initial ICU and hospital admission were longer for patients with sepsis: 10.1?±?11.9 vs. 8.0?±?9.8 days (p?<?0.0001) and 22.8?±?21.2 vs. 19.1?±?19.0 days, (p?=?0.0003) respectively. The cost of ICU admissions was higher for patients with sepsis: A$43,345?±?46,263 (€35,109?±?35,043) versus 34,844?±?38,281 (€28,223?±?31,007), mean difference $8501 (€6885), 95% CI $4342–12,660 (€3517?±?10,254), p?<?0.001 as was the total cost of hospital treatment to 2 years: A$74,120?±?60,750 (€60,037?±?49,207) versus A$65,806?±?59,856 (€53,302?±?48,483), p?=?0.005.

Conclusions

Critically ill patients with sepsis have higher healthcare resource use and costs but similar survival and HRQoL compared to matched patients without sepsis.

     

Current status of the rheumatologists’ workforce in Latin America: a PANLAR collaborative study

Clinical Rheumatology - Studies conducted by various scientific societies have shown that the demand for specialized rheumatology care is greater than the projected growth of the workforce. Our...     

Calcitonin secretion by monolayer cultures of human C-cells derived from medullary thyroid carcinoma.

Monolayer cultures of human calcitonin-secreting cells (C-cells) have been derived from medullary thyroid carcinomas. The cultures were prepared from cell suspensions obtained by enzymatic digestion of surgical specimens of the tumor. Human calcitonin (hCT) secretion by these cells was studied using a specific radioimmunoassay for the hormone. The cultures could be used for reproducible secretion studies up to 40 days after their initiation; they demonstrated a linear rate of hormone secretion in the basal state for at least 4 h. Calcium, pentagastrin, and prostaglandin E2 (PGE2) each produced a marked increase (up to 7-fold) in hormone secretion. Magnesium had no apparent secretory effect; and compared to PGE2, PGF2alpha had only a small secretory effect. In addition to responding to specific secretagogues shown to regulate calcitonin secretion in vivo, the secretory effects of each of the secretagogues could be raipdly reversed. Therefore, these cultures of human C-cells exhibit secretory responses which are quantitatively and qualitatively similar to C-cells in vivo. Accordingly, such cultures provide a useful model to study the regulation of calcitonin secretion in human C-cells.     

Preexisting cardiopulmonary disease attenuating the atrial natriuretic peptide response. Results in patients with acute respiratory failure.

The purpose of this study was to evaluate the pathophysiologic role of atrial natriuretic peptide (ANP) as a pulmonary artery vasodilator in patients with acute respiratory failure receiving artificial ventilation. Twenty-one consecutive patients were studied, 12 without and 9 with preexisting cardiopulmonary disease. Pulmonary artery plasma ANP levels were significantly higher than the levels obtained in the superior vena cava and radial artery. Plasma ANP levels correlated significantly with the plasma levels of its second messenger, guanosine 3',5'-cyclic monophosphate (cGMP). In the 12 patients without prior cardiopulmonary disease, plasma ANP levels correlated significantly with mean pulmonary arterial pressure (MPAP). This correlation was not found in the nine patients with preexisting cardiopulmonary disease. The cGMP/ANP ratio, indicating the biologic effect of ANP, was also higher in the patients without preexisting cardiopulmonary disease. These results are compatible with clearance and vasodilator activity of ANP in the pulmonary vascular bed, but only in patients without preexisting cardiopulmonary disease.     

Prognostic value of thallium-201 exercise scintigraphy in low-risk patients after Q-wave myocardial infarction: comparison with exercise testing and catheterization.

In a prospective study of 100 consecutive patients discharged after a Q-wave myocardial infarction, the value of reversible ischemia on thallium-201 scintigraphy to assess the risk of cardiac events (death or reinfarction) during 4 years was compared with variables from exercise testing and cardiac catheterization. Patients with markedly impaired left ventricular function [ejection fraction (EF) < or = 0.30] were excluded. During follow-up there were 20 cardiac events (10 cardiac deaths and 10 reinfarctions). Thallium-201 scintigraphy was significantly better than all exercise test variables and better than an EF < 0.40, with good sensitivity and specificity (75 and 51%, respectively). Exercise-induced reversible ischemia on scintigraphy yielded the same information as the presence of multivessel disease. Exercise test variables were of limited value to assess prognosis. Thus, thallium-201 scintigraphy can be used as the only tool to predict future cardiac events in low-risk patients after a Q-wave myocardial infarction.     

Relation between plasma fibroblast growth factor-23, serum fetuin-A levels and coronary artery calcification evaluated by multislice computed tomography in patients with normal kidney function

Objective To examine the correlation of plasma fibroblast growth factor (FGF)‐23 and serum fetuin A levels with the coronary artery calcification score (CACS) in patients with normal kidney function. Background Vascular calcification is an active process that may be aggravated by hyperphosphataemia and hypercalcaemia. FGF‐23 and human fetuin‐A have been associated with calcifying arteriosclerosis in renal failure. Plasma FGF‐23 was identified as an independent factor negatively associated with peripheral vascular calcification. Fetuin‐A acts as a systemic inhibitor of ectopic calcification in dialysis patients and can be correlated to the survival of these patients. Very few data exists on the role of FGF‐23 and fetuin‐A in coronary calcification of patients without impaired kidney function. Materials and methods Sixty‐four patients, 21 females and 43 males, were subjected to 64‐slice coronary computed tomography (CT) to evaluate coronary artery calcification (CAC). Plasma intact FGF‐23 was determined by ELISA. Serum fetuin‐A concentration were evaluated nephelometrically. Results Mean plasma FGF‐23 level was 20·4 ± 9·1 pg/ml and serum fetuin‐A was 0·46 ± 0·09 g/l. There was no correlation between FGF‐23 (P = 0·777) and fetuin‐A (P = 0·767) levels and the CACS. No correlation was found between the presence of noncalcified plaques and coronary artery stenosis (CAS) ≥  50%, and FGF‐23 (P = 0·313 and P = 0·775) and fetuin‐A levels (P = 0·601 and P = 0·659). Conclusion Plasma intact FGF‐23 and serum fetuin‐A concentration do not correlate with the CACS, the grade of stenosis or presence of noncalcified plaques of the coronary arteries in patients with normal kidney function.