Erythrocyte membrane properties in cystic fibrosis

The biochemical properties of the erythrocyte membrane have been studied in cystic fibrosis patients and in age-matched controls. No significant differences could be observed in either the concentration or composition of the principal membrane constituents. Contrary to previous reports, we found normal levels of the Mg²⁺-dependent and Ca²⁺ + Mg²⁺-dependent ATPase activities in CF preparations. However, a qualitative difference was observed in the Ca²⁺-dependent ATPase, since the enzyme had relatively greater activity at lower calcium concentrations in the cystic preparations. This effect on the membrane-bound Ca²⁺-ATPase is unlikely to represent a genetic defect in the enzyme itself but it may be connected with the mechanism of pathogenesis in cystic fibrosis.     

Azithromycin for improving pulmonary function in cystic fibrosis

OBJECTIVE: To review the literature concerning the use of azithromycin in the treatment of patients with cystic fibrosis (CF). DATA SOURCES: A search of MEDLINE (1966-April 2004), Embase (1980-April 2004), and International Pharmaceutical Abstracts (1971-April 2004) was performed. Search terms included cystic fibrosis, macrolide, and azithromycin. DATA SYNTHESIS: Four studies have been performed in 7-185 patients (children and adults) over a 3- to 6-month period. The azithromycin dosage ranged from 250 mg 3 times weekly to 500 mg daily. The trials reported an improvement in percent predicted forced expiratory volume ranging from 2.95% to 6.2% in patients treated with azithromycin compared with those receiving placebo. CONCLUSIONS: Azithromycin appeared to improve pulmonary function in adults and older children with CF and was well tolerated when administered for 6 months. Further research is needed to determine an optimal dosage regimen, duration of treatment, effects on quality of life, and cost-effectiveness of azithromycin therapy.     

Recovery of airway cystic fibrosis transmembrane conductance regulator function in mice with cystic fibrosis after single-dose lentivirus-mediated gene transfer

The potential for gene therapy to be an effective treatment for cystic fibrosis (CF) airway disease has been limited by inefficient gene transfer vector particle delivery and lack of persistent gene expression. We have developed an airway conditioning process that, when combined with a human immunodeficiency virus (HIV)-derived lentivirus (LV) vector, resulted in persistent in vivo expression of transgenes in airway epithelium. Pretreatment of mouse nasal epithelium with the detergent lysophosphatidylcholine (LPC) prior to instillation of a single dose of an LV vector carrying the LacZ marker gene produced significant LacZ gene expression in nasal airway epithelium for at least 92 days. Transduction of the cystic fibrosis transmembrane conductance regulator (CFTR) gene using the same LV vector system resulted in partial recovery of electrophysiologic function in the nasal airway epithelium of CF mice (cftr(tm1Unc) knockout) for at least 110 days. This first demonstration of LV-mediated in vivo recovery of CFTR function in CF airway epithelium illustrates the potential of combining a preconditioning of the airway surface with a simple and brief LV vector exposure to produce therapeutic gene expression in airway.     

Effects of methaqualone on blood platelet function

To study the mechanism whereby toxic doses of methaqualone cause a bleeding tendency in humans, the effects of methaqualone, diphenhydramine, and the combination of methaqualone plus diphenhydramine on blood platelet function were investigated. Exposure of human platelets in platelet-rich plasma in vitro to final concentrations of methaqualone ranging from 1.1 to 4.5 X 10(-4)) M resulted in nearly complete inhibition of the secondary phase and significant inhibition of the primary phase of adenosine diphosphate (ADP)--induced aggregation. Both the slope and height of collagen-induced aggregation responses were reduced significantly in vitro by the drug. When methaqualone final concentrations of 1.1, 2.3, and 4.5 X 10(-4) M were studied in the presence of diphenhydramine (1.1, 2.3, and 4.5 X 10(-5) M, respectively), the degree of inhibition of ADP-induced aggregation was only slightly greater (not significant) than that observed with methaqualone. The platelets of rabbits injected intravenously with methaqualone, 10 mg/kg, demonstrated a significantly decreased ability to aggregate with ADP and collagen 30 and 60 min after administration of the drug. These results suggest that a drug-induced defect of blood platelet function may play a role in the bleeding associated with methaqualone toxicity.     

Red cell membrane Ca-ATPase in cystic fibrosis: increased activation by Na

In the present study, we compared the kinetics of activation by Na, of red cell membrane Ca-ATPase of cystic fibrosis (CF) patients and healthy volunteers (controls). Calmodulin (membrane-free hemolysate) was included in the assay medium to promote maximal Ca-ATPase activation. There were no significant differences between the red cell Ca-ATpase activities of the two groups, assayed either in the absence or in the presence of optimal concentrations of Na. There were also no significant differences between the apparent dissociation constants or Hill coefficients for activation of red cell Ca-ATPase by Na. On the other hand, the percent activation by Na of red cell Ca-ATPase activity of the CF patients was approximately 40% greater than that of the controls. The additional increment of Ca-ATPase activity due to the elevated percent activation was about 14% of the total red cell Ca-ATPase activity of the CF patients. Although this increment of Ca-ATPase activity is relatively small, the increased percent activation by Na does suggest an alteration in the enzyme's response to Na. At present we do not know whether or not this alteration applies to Ca-transport or if it is of any pathophysiological importance.     

氯吡格雷抑制血小板功能的两种检测方法比较：血小板聚集实验与血小板膜糖蛋白检测

目的:采用血小板聚集实验及血小板膜糖蛋白检测两种方法,观察比较正常人口服氯吡格雷后抑制血小板功能情况,寻求简便、经济、可靠、合理的氯吡格雷剂量监测方法。方法:①选取2006-03/05在解放军总医院进行体检的40名健康志愿者,对本实验均知情同意,随机数字表法分为4组,10名/组:第1组一次性服用75mg氯吡格雷;第2组服用氯吡格雷75mg/d,连服3d停药;第3组服用氯吡格雷75mg/d,连服7d停药;第4组一次性服用300mg氯吡格雷。②各组分别于服药前、停药后1,2,4,6,8,10d这7个时间点取样;此外,第2组另于服药3d后取样一次,第3组另于服药7d后取样一次,第4组另于服药后2h和8h各取样一次。③于给药前后各时间点,采用血小板聚集仪检测血小板聚集率,流式细胞仪检测血小板膜糖蛋白PAC-1及CD62p活性,各指标间进行相关分析。结果:40名健康志愿者均进入结果分析。①各组不同时间点血小板聚集率及血小板膜糖蛋白PAC-1和CD62p活性检测:CD62p变化幅度最大且不易恢复至服药前水平,PAC-1变化幅度最小且容易恢复至服药前水平,血小板聚集率变化幅度介于PAC-1和CD62p之间。②各组不同时间点血小板聚集率与血小板膜糖蛋白PAC-1和CD62p活性的相关分析:服药前后各时间点血小板聚集率与血小板膜糖蛋白PAC-1,CD62p均成正相关(r最大=0.666,P<0.01;r最大=0.755,P<0.05);PAC-1与CD62p亦呈正相关(r最大=0.728,P<0.01)。结论:口服氯吡格雷后,血小板聚集率与血小板膜糖蛋白PAC-1,CD62p活性这3个血小板功能指标变化具有较好的相似性。提示血小板聚集试验为氯吡格雷剂量监测简捷、实用、有效的方法之一。     

Effects of sodium piperacillin on platelet function in normal volunteers

Piperacillin is a new semisynthetic penicillin which is similar in structure to carbenicillin and ticarcillin. Since the latter antibiotics have been shown to cause abnormalities in hemostasis, we studied the effects of piperacillin on blood coagulation and platelet function. Fifteen healthy volunteers received the drug in doses of either 100, 200, or 300 mg/kg per day for a period of 7 days. Serial studies showed no abnormalities in blood coagulation in any subject. Decreased platelet aggregation responses to adenosine diphosphate, epinephrine, collagen, and achidonic acid were commonly noted, but prolongation of the bleeding time occurred in only 3 of 15 subjects after 7 days of piperacillin administration. These results suggest that although piperacillin also induces platelet dysfunction, these effects may be less than those caused by ticarcillin or carbenicillin at an equivalent dosage.     

Effects of apalcillin on platelet function in normal volunteers.

We investigated the effects of apalcillin on blood coagulation and platelet function. The drug was administered to 21 human volunteers in daily intravenous doses of 75, 150, and 225 mg/kg. These doses evoked abnormalities in platelet aggregation similar to those found with piperacillin and mezlocillin and less striking than those produced by carbenicillin and ticarcillin. Plasma coagulation as measured by prothrombin time, activated partial thromboplastin time, thrombin time, and fibrinogen concentration was not affected. There were consistent and major reductions in plasma antithrombin III activity, particularly at the two higher dose levels. Of 21 patients, 7 (33%) also manifested maculopapular skin rashes which resolved after discontinuation of the drug.     

Nutritional management in cystic fibrosis — an alternative perspective in gastrointestinal function

Summary

The gastrointestinal problems in cystic fibrosis (CF) may limit energy and nutrient availability and also cause symptoms such as abdominal pain and disturbed bowel habit which may further suppress appetite or alter the diet. Taken together this may lead to an inadequate supply of energy and nutrients to meet the nutritional requirements of the individual resulting in restricted growth or weight loss. A failure to optimize the digestive and absorptive capacity of the gastrointestinal tract places greater emphasis upon nutritional management by food intake alone. Practitioners need to focus more on gastrointestinal dysfunction in CF and its impact upon food intake in order to improve the efficacy of nutritional management. Refined stable isotopic tracers allow further exploration of the pathophysiology of the gastrointestinal tract in terms of nutrient availability. In clinical practice, a closer assessment of gastrointestinal function is supported by the use of simple, noninvasive tools which, both objectively and systematically, characterize those patients who have problems.     

Impaired beta adrenergic receptor binding and function in cystic fibrosis neutrophils.

Cystic fibrosis (CF), a genetic disease characterized by abnormalities of exocrine gland and mucociliary function, has recently been shown to be associated with abnormal adrenergic and cholinergic physiologic responses in addition to decreased beta adrenergic-induced cyclic AMP generation in human leukocytes. In this study we have attempted to elucidate the nature of this hyporesponsiveness by assessing beta adrenergic receptor number and affinity (KD) in the intact neutrophil using the antagonist ligand [3H] dihydroalprenolol and cyclic AMP responses to isoproterenol in addition to histamine, and prostaglandin E1 in CF subjects, CF obligate heterozygotes (CFH), and normal control subjects. CF patients had significantly less (p less than 0.025) cyclic AMP stimulation above basals levels with isoproterenol (0.1 microM to 0.1 mM), compared with control values, but no consistent differences between groups were noted with histamine or PGE1. CF neutrophils had significantly fewer (p less than 0.005) beta adrenergic receptors per neutrophil (398.0 +/- 54.2 vs. 819.4 +/- 67.2) compared with control neutrophils, but the KD (0.740 +/- 0.11 vs. 0.630 +/- 0.05 nM) did not differ significantly (p greater than 0.05). There was no correlation between clinical severity and either cyclic AMP generation or dihydroalprenolol binding (r = 0.27 and 0.24, respectively, p greater than 0.05). The CFH group had approximately 50% of the cyclic AMP stimulation compared with controls, but the number (909.8 +/- 89.3) and KD (0.710 +/- 0.09 nM) of their beta adrenergic receptors were indistinguishable from control subjects. These findings suggest "down regulation" of the beta receptor in the CF patient. The cause of this remains unknown. Although the etiology of the decreased cyclic AMP responses in CFH was not due to decreased beta adrenergic receptors as assessed by antagonist ligand binding, further studies inthe CFH group to include agonist binding, receptor-adenylate cyclase coupling, intrinsic adenylate cyclase activity, and catecholamine metabolism may help determine the basic cause of beta adrenergic hyperesposiveness in both CFH and CF.     

Effects of plasma membrane Ca2+-ATPase tyrosine phosphorylation on human platelet function

BACKGROUND: The plasma membrane Ca(2+)-ATPase (PMCA) plays an essential role in maintaining low intracellular Ca(2+) ([Ca(2+)](i)) in resting platelets. Earlier studies demonstrated that platelet activation by thrombin results in tyrosine phosphorylation of PMCA, which inhibits pump activity. OBJECTIVES: The objective was to determine the functional consequences of PMCA tyrosine phosphorylation. METHODS: A decapeptide including the tyrosine phosphorylation site of PMCA and a scrambled version were synthesized and introduced into human platelets using saponin. Fura-2 calcium monitoring and aggregometry were used to characterize the effects of inhibition of tyrosine phosphorylation. RESULTS: Western blot analysis of immunoprecipitates showed that introduction of the inhibitory peptide decreased tyrosine phosphorylation of PMCA by nearly 60% in saponin-permeabilized, thrombin-treated platelets as compared with the scrambled control peptide. Concomitant with inhibition of PMCA tyrosine phosphorylation was a significant decrease in [Ca(2+)](i) during thrombin-mediated platelet activation. The functional consequence of reduced PMCA tyrosine phosphorylation and decreased [Ca(2+)](i) was a significant delay in the onset of thrombin-mediated platelet aggregation. CONCLUSIONS: The results demonstrate that PMCA tyrosine phosphorylation regulates [Ca(2+)](i) during platelet activation, which affects downstream events in the activation process. Moreover, PMCA tyrosine phosphorylation and resultant inhibition of PMCA activity produces a positive feedback loop mechanism by enhancing the increase in [Ca(2+)](i) accompanying platelet activation.     

Antibacterial therapy in cystic fibrosis

Bacterial lung infections determine the prognosis for most cystic fibrosis patients. The antibacterial therapy is difficult because of the host-bacterium interaction and altered pharmacokinetics. The new insights in the working mechanisms of antibiotics that may lead to better treatment results have been discussed, and guidelines for treatment of lung infections in cystic fibrosis patients were given.     

Bronchial allergy in cystic fibrosis

Thirty-one patients with cystic fibrosis (CF) were thoroughly evaluated for allergy. This included a clinical history, skin tests with twenty-three allergens and bronchial provocation with inhaled allergens and histamine. The bronchial response was measured by whole body plethysmography. Of the patients studied, 40% showed a bronchoconstrictor response to inhaled allergens, despite the fact that none had reported asthma in their clinical history. Strong skin test reactions (3+ and 4+) and weak reactions (2+) were associated with 65% and 4% of positive reactions of the airways respectively. Weak skin reactions with Aspergillus fumigatus, however, were associated with 43% of positive bronchial challenges. In addition to Aspergillus, the mould Alternaria tenuis was found to be an important allergen causing a bronchial response in CF patients. There was no correlation between the thresholds of bronchial sensitivity to allergen and histamine, suggesting that the pathogenetic mechanisms of CF and bronchial asthma are different.