Correlation of factor IXa subsite modulations with effects on substrate discrimination

BACKGROUND

A key feature of factor IXa is its allosteric transformation from an enzymatically latent form into a potent procoagulant. Although several small molecules have been found to be capable of partially affecting FIXa function (i.e. ethylene glycol, Ca(2+), and low molecular weight heparin [LMWH]), the resulting modest changes in peptidolytic activity have made the study of their mechanisms of action challenging. As these effects provide hints about potential regulatory forces that may be operational in the full expression of FIXa coagulant activity, their description remains of great interest. Studies of crystal structures have yielded insights into the structural changes induced by these effectors, but there remains a paucity of information to correlate any given structural change with specific consequences for FIXa function.

OBJECTIVES

To correlate structural changes induced by these modulators with defined consequences for FIXa substrate discrimination and function.

METHODS

A peptidomics-based mass spectrometry (MS) approach was used to examine the patterns of hydrolysis of four combinatorial chemistry-derived pentapeptide libraries by FIXa under various conditions in a soluble, active enzyme system.

RESULTS

Ethylene glycol specifically altered the S3 subsite of FIXa to render it more tolerant to side chains at the P3 substrate position, whereas Ca(2+) enhanced tolerance at the S2 subsite. In contrast, LMWH altered both the S2 and S1' subsites.

CONCLUSIONS

These results demonstrate the role of plasticity in regulating FIXa function with respect to discrimination of extended substrate sequences, as well as providing crucial insights into active site modulations that may be capitalized on by various physiologic cofactors of FIXa and in future drug design.

Scintigraphic measurement of tracheal mucus velocity in vivo

Mucociliary clearance (MCC) is an important mechanism for removing inhaled particles, secretions and cellular debris from the respiratory tract. Here, a direct measurement of tracheal mucus velocity (TMV) for assessment of MCC, suitable for clinical and research use, is reported, and a comparison is made of TMV in normal subjects and patients with chronic obstructive pulmonary disease (COPD). A 0.1-mL bolus of radiolabelled (2-5 MBq), technetium-labelled macroaggregated human albumin (99mTc MAA) was injected through the cricothyroid membrane into the trachea of 20 young (< 50 yrs) and 12 older (> 50 yrs) normal subjects and 34 patients with COPD. Repeat studies were carried out in 13 normal subjects and 16 COPD patients. Movement of the bolus in the trachea was recorded (15 min) using a gamma camera interfaced to a computer. Data were analysed using specifically designed software. The test was well tolerated by subjects and patients, and no significant adverse events were reported. No significant differences were observed between data recorded from different regions of the bolus (leading edge, peak, trailing edge) by analysis of variance (ANOVA). Bland-Altman plots of the repeat studies indicated that data were more variable in normal subjects (coefficient of repeatability (COR) 10.3 mm.min-1) than in COPD patients (COR 5.5 mm.min-1). TMV (mean +/- SD) in young normal subjects (n = 20) was 10.7 +/- 3.5 mm.min-1. TMV was reduced in older normal subjects (n = 12; 6.5 +/- 2.6 mm.min-1) and further reduced in COPD (n = 34; 2.1 +/- 2.7 mm.min-1). In conclusion, this technique can be used to measure tracheal mucus velocity rapidly and safely in healthy subjects and patients with respiratory tract disease. This study has confirmed that tracheal mucus velocity declines with age and is further impaired in patients with chronic obstructive pulmonary disease.

Accuracy in gamma camera measurements of point source velocities

Mucociliary clearance is impaired in many diseases of the respiratory system. We have developed a method for measuring tracheal mucus velocity by the dynamic study of a single point source of radioactivity deposited in the trachea by cricothyroid injection. Preliminary results suggest that patients with airways disease have very low tracheal mucus velocities (<2 mm x min(-1)). The aim of this experiment was to explore the ability of current scintillation detection systems to track a single point as it moves in a dynamic study in small increments and at low velocity (movements of the order of 1 mm). Background noise was estimated to contribute an error in positioning of 0.16 mm (1 standard deviation). Overall errors in velocity were estimated at 0.2 mm x min(-1). This suggests that standard instrumentation in use in most nuclear medicine departments has the capacity to measure accurately velocities as low as 1 mm x min(-1).

Ciliary defects in healthy subjects, bronchiectasis, and primary ciliary dyskinesia

To develop criteria to aid in the diagnosis of primary ciliary dyskinesia (PCD) we analyzed quantitatively the incidence and the range of ciliary ultrastructural abnormalities in healthy subjects and in patients with respiratory tract disease. The beat frequency and ultrastructure of nasal respiratory tract cilia, including ciliary orientation, were measured in 62 healthy subjects (31 nonsmokers, 20 exsmokers, and 11 smokers), ranging in age from 1 to 76 yr, and in 51 patients with respiratory tract disease. In healthy subjects, ciliary beat frequency (CBF) ranged between 9.6 and 15.3 Hz, the incidence of microtubule defects varied between 0 to 9%, the mean number of inner dynein arms per cilium ranged from 3.0 to 7.1, and the mean number of outer dynein arms per cilium ranged from 7.4 to 9.0. The deviation of cilia in healthy subjects varied between 8 and 29 degrees. By comparing the data for ciliary defects in healthy subjects with the data obtained from patients with respiratory disease, we identified two patient groups: patients with PCD (n = 31) and patients with respiratory tract disease not due to PCD. For comparison with the PCD patients, a group of 20 patients with bronchiectasis was selected and analyzed. Patients with PCD had significantly lower CBF (p < 0.001), significantly higher incidences of peripheral and central tubule defects (p < 0.01), and greater ciliary disorientation (p < 0.005). There was a strong correlation between CBF and the number of outer dynein arm numbers, but not with inner dynein arm numbers, suggesting that inner and outer dynein arms may play different functional roles in producing ciliary motility.(ABSTRACT TRUNCATED AT 250 WORDS)

Mucociliary function, ciliary ultrastructure, and ciliary orientation in Young's syndrome

BACKGROUND

Mucociliary clearance is impaired in patients with Young's syndrome (obstructive azoospermia with recurrent sinobronchial disease), cystic fibrosis, and primary ciliary dyskinesia. No defect of cilia or mucus has been detected in Young's syndrome.

METHODS

Ciliary function and ultrastructure, including ciliary orientation, were studied quantitatively in 20 patients with Young's syndrome and 20 normal subjects to determine the incidences of ciliary defects. Nasal ciliated epithelium was obtained from each subject and used for measurement of ciliary beat frequency and ultrastructural analyses. Ciliary orientation was determined by measuring ciliary deviation in electron micrographs; ciliary deviation is a measure of the relative orientation of cilia in relation to each other in which high values indicate ciliary disorientation.

RESULTS

Ciliary beat frequency and the incidence of microtubular defects and numbers of dynein arms did not differ between patients with Young's syndrome and control subjects. In patients with Young's syndrome basal ciliary deviation (16.0 degrees) was similar to that in control subjects (14.1 degrees), but at the ciliary tip ciliary deviation (21.9 degrees) was greater than in healthy subjects (14.5 degrees).

CONCLUSION

The relative disorientation of the distal ciliary axoneme in patients with Young's syndrome compared with normal subjects may be due to a structural defect but is more likely to be a consequence of abnormal mucus.

Giant pericardial cyst

We report the excision of the largest pericardial cyst yet described. Despite causing collapse of the left lower lobe, and bronchitis, an excellent symptomatic result was obtained.

Orientation of respiratory tract cilia in patients with primary ciliary dyskinesia, bronchiectasis, and in normal subjects

A reproducible technique, utilising a graphics tablet and a personal computer for measuring ciliary orientation from electron micrographs of ciliated epithelium, was assessed. Ciliary deviation was measured in 47 normal subjects (mean ciliary deviation +/- 1 SD was 14.6 (3.3 degrees)), in eight patients with bronchiectasis and normal ciliary function (15.1 (6.5 degrees], and in seven patients with primary ciliary dyskinesia (38.7 (7.8 degrees); significantly greater than the first two groups). Measurements of ciliary deviation at the tip, base, and basal feet showed very little variation along the ciliary shaft in all three groups, suggesting that valid measurements of ciliary deviation can be made at any level of the cilium. Mean ciliary deviation in normal subjects was always less than 30 degrees; all patients with a mean ciliary deviation of greater than 30 degrees had recurrent respiratory tract disease. Four of seven patients with primary ciliary dyskinesia had ciliary disorientation; in one this was the only defect. Measurements of inter- and intraobserver variability using this method showed a maximum difference between observations of 4.1 degrees. It is suggested that ciliary orientation should be measured in patients suspected of having defective ciliary function or structure, or both.

Primary malignant non-seminomatous germ cell tumour of the mediastinum treated by surgery and chemotherapy

Primary malignant germ cell tumours of the mediastinum are rare and are associated with poor survival when treated with surgery alone or with surgery when chemotherapy has failed. Recent improvements in combination chemotherapy have given some prospect of cure. A patient treated with primary surgical excision and postoperative chemotherapy, who remains free of disease 24 months after completion of treatment is reported here.

Cystic fibrosis serum does not inhibit human ciliary beat frequency

The effect of cystic fibrosis (CF) serum on human respiratory tract ciliary beat frequency (CBF) was studied to investigate the possible relevance of CF-serum-induced disruption of rabbit tracheal ciliary motility to human disease. Nasal ciliated epithelium from patients with CF and from normal subjects was incubated at 37 degrees C in CF serum, in normal human serum (NHS), or in nutrient medium. CBF was measured photometrically at time intervals up to 3 h. The effect of CF serum on human trachea and of CF serum, NHS, and rabbit serum on rabbit tracheal CBF was also studied. Mean CBF for all the normal and CF nasal cilia incubated in CF serum, NHS, or nutrient medium was not significantly different and did not fall during 3 h. Human tracheal CBF did not fall during 3 h. The CBF for rabbit trachea in rabbit serum did not slow and rabbit trachea in NHS slowed after 150 min. Rabbit trachea in CF serum beat more slowly than all the other groups (p less than 0.001) progressing to ciliostasis between 45 and 150 min. We conclude that human respiratory tract ciliary motility, as measured by CBF in vitro, is unaffected by factors in CF serum that impair rabbit tracheal ciliary activity.

An in vitro model for studying the effects of pharmacological agents on human ciliary beat frequency: effects of lignocaine

1 The effects of lignocaine hydrochloride on ciliary beat frequency (CBF), measured photometrically in vitro, using human epithelium obtained by nasal brushing was studied in 20 healthy subjects. Above lignocaine concentrations of 2.5 x 10(-3) g/ml cilio-inhibition occurred in a dose-dependent manner. Concentrations greater than 2 x 10(-2) g/ml caused ciliostasis. 2 Lignocaine aerosol was sprayed in vivo on the mucosa of one nasal cavity in five healthy subjects and five patients premedicated for bronchoscopy. CBF, measured in vitro in nasal brushings, was not different for treated and untreated sides. 3 Variation of intrinsic CBF with time after nasal brushings were taken was studied in ten normal subjects. No significant change in CBF was found until after 24 h. 4 We conclude that lignocaine hydrochloride, at concentrations three orders of magnitude above drug levels encountered in clinical practice, inhibits human CBF in a dose-dependent manner. Aerosolised lignocaine hydrochloride in doses which produce local nasal mucosal anaesthesia, does not inhibit CBF subsequently measured in vitro. Lignocaine is a suitable local anaesthetic for use at fibreoptic bronchoscopy when samples are being obtained for study of ciliary function. 5 The measurement of CBF in nasal mucosal brushings provides an in vitro model suitable for studying the effects of pharmacological agents on human ciliary activity.

Transitory ultrastructural abnormalities of cilia

We report a patient with chronic respiratory tract disease and ultrastructural abnormalities of nasal cilia at first interpreted as being consistent with a primary ciliary defect. Subsequent sampling of nasal ciliated epithelium from the same area failed to reveal the defects of structure. Abnormalities of ciliary ultrastructure found on a single occasion, especially in the presence of acute inflammation, should be interpreted with caution.

Nasal brushing for the study of ciliary ultrastructure

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Human ciliary beat frequency in epithelium from intrathoracic and extrathoracic airways

Respiratory tract ciliary beat frequency (CBF) was studied to investigate the relation between nasal and tracheal CBF and the possible existence of a gradient of ciliary activity in the human tracheobronchial tree. Ciliary beat frequency was measured photometrically in nasal, tracheal, and lower lobe bronchial brushings obtained at bronchoscopy in 25 patients and in nasal, tracheal, and subsegmental airway brushings in a further 12 patients. Mean (+/- 1 SD) beat frequencies for nasal, tracheal, lower lobe bronchial, and subsegmental samples were 14.0 +/- 1.5, 14.2 +/- 1.3, 14.3 +/- 1.5, and 10.3 +/- 1.0 beats/s, respectively. Nasal, tracheal, and lower lobe bronchial beat frequencies were not significantly different (p greater than 0.05), but subsegmental airway CBF was slower than each of the others (p less than 0.001); there was a positive correlation between nasal and tracheal CBF (r = 0.71). We conclude that CBF is slower in human peripheral airways, but that nasal and tracheal rates are similar.

Nasal brushing and measurement of ciliary beat frequency. An in vitro method for evaluating pharmacologic effects on human cilia

Human respiratory tract epithelium suitable for measuring ciliary beat frequency (CBF) may be obtained by nasal brushing. We have used such ciliated epithelium in an in vitro preparation to study the effects on CBF of lidocaine hydrochloride administered topically in vivo before brushing or in vitro after brushing. Beat frequency measured after in vivo administration was unchanged compared to control values while incubating ciliated epithelium in vitro in increasing concentrations of lidocaine resulted in dose-related cilioinhibition. Drug concentrations required to depress ciliary activity in vitro were much higher than those occurring in clinical practice.

Nasal mucociliary clearance and ciliary beat frequency in cystic fibrosis compared with sinusitis and bronchiectasis

Nasal ciliary function and mucociliary clearance were studied in patients with cystic fibrosis and in three control groups. Ciliary beat frequency and nasal clearance time were measured in groups of 10 subjects with cystic fibrosis, sinusitis and bronchiectasis and age and sex-matched control subjects. Ciliary beat frequency was also measured in normal subjects matched as bronchiectasis controls. Cystic fibrosis patients and their controls, patients with sinusitis, and the bronchiectasis controls did not differ in ciliary beat frequency, but it was slower in the patients with bronchiectasis (p less than 0.05). Nasal mucociliary clearance in cystic fibrosis and bronchiectasis was slower than in the cystic fibrosis controls (p less than 0.001) and in patients with sinusitis (p less than 0.01). The finding of a normal beat frequency in cystic fibrosis cilia studied in vitro together with abnormal nasal mucociliary clearance measured in vivo in the same patients suggests the existence of an abnormality of mucus in vivo. The innate function of cystic fibrosis cilia, as measured in vitro by beat frequency, is normal.

The maximum expiratory flow-volume curve with air and a low-density gas misture. An analysis of subject and observer variability

The subject and intra- and inter-observer variability of three measurements derived from the maximal expiratory flow-volume (MEFV) curve with air and helium-oxygen (HeO2) mixture was determined in ten normal subjects who produced curves in the morning and afternoon of three consecutive days and again on one day a month later. The measurements examined were the maximum flow at 50% vital capacity (V50), the percentage increases in V50 when breathing the He-O2 mixture (delta V50), and the volume at which the curves on air and He-O2 first meet or intersect (VisoV). The delta V50 and VisoV were shown to have a greater degree of variability than the V50 and, in the case of VisoV, this was contributed to significantly by the observer variability. The within-subject variability of the delta V50 and VisoV was so great that the usefulness of these tests in following changes in lung function of individual patients must be questioned.

Plasma and sputum erythromycin concentrations in chronic bronchitis

Plasma and sputum concentrations of erythromycin were measured in 10 patients with chronic bronchitis during an eight-day course of a new formulation of erythromycin stearate. The plasma erythromycin levels compared favourably with the minimal inhibitory concentrations for common respiratory pathogens and indicated adequate gastrointestinal absorption when the drug was taken immediately before food. Sputum erythromycin levels were variable and in some patients low or undetectable. Measurable sputum erythromycin levels were approximately 10% of plasma levels with no evidence of accumulation and were of similar order of magnitude to the minimal inhibitory concentrations for common respiratory pathogens except Haemophilus influenzae. There was no correlation between sputum and plasma erythromycin levels. There was a trend for higher erythromycin levels in sputum containing increasing amounts of pus and also when plasma levels increased.

The influence of food on the bioavailability of new formulations of erythromycin stearate and base

1. The effect of food on the bioavailability of two new formulations of erythromycin, 1) erythromycin stearate, 500 mg (Erythrocin, 250 mg capsule-shaped tablets) and 2) erythromycin base, 500 mg (Eryc, 250 mg capsules containing enteric-coated pellets) was studied in 16 healthy subjects. 2. The study was a balanced, randomized Latin square design and was conducted on 4 days. The four treatments were erythromycin stearate immediately before (EB) and after EA) breakfast and erythromycin base immediately before (eB) and after (eA) breakfast. 3. The mean +/- s.d. maximal plasma erythromycin concentrations were 2.09 +/- 1.06, 0.37 +/- 0.40, 1.8+ +/- 1.15 and 1.91 +/- 1.57 micrograms/ml and the mean +/- s.d. times at which these occurred were 1.3 +/- 0.7, 2.3 +/- 0.9, 4.4 +/- 1.9 and 4.3 +/- 1.1 h for EB, EA, eB and eA respectively. 4. The mean +/- s.d. areas under the curves (0 to 8 h) were 4.99 +/- 2.41, 1.04 +/- 1.57, 4.93 +/- 2.98 and 4.98 +/- 3.14 for EB, EA, eB and eA respectively. 5. The bioavailability of erythromycin stearate was significantly reduced by the prior administration of food, whereas the absorption of the base was not inhibited by food.

Plasma and saliva concentrations for a new formulation of erythromycin stearate

Erythromycin saliva and plasma concentrations were determined in 10 subjects after the first and fourth doses of a new formulation of erythromycin stearate ('Erythrocin'), 500 mg 8-hourly, taken immediately before food. Consistent absorption occurred and the steady state plasma levels compared favourably with the minimal inhibitory concentrations of erythromycin for common respiratory pathogens. There was a significant positive correlation between steady state saliva and plasma levels.