Comparing ultrastable lasers at 7 × 10-17 fractional frequency instability through a 2220 km optical fibre network

Ultrastable lasers are essential tools in optical frequency metrology enabling unprecedented measurement precision that impacts on fields such as atomic timekeeping, tests of fundamental physics, and geodesy. To characterise an ultrastable laser it needs to be compared with a laser of similar performance, but a suitable system may not be available locally. Here, we report a comparison of two geographically separated lasers, over the longest ever reported metrological optical fibre link network, measuring 2220 km in length, at a state-of-the-art fractional-frequency instability of 7 × 10-17 for averaging times between 30 s and 200 s. The measurements also allow the short-term instability of the complete optical fibre link network to be directly observed without using a loop-back fibre. Based on the characterisation of the noise in the lasers and optical fibre link network over different timescales, we investigate the potential for disseminating ultrastable light to improve the performance of remote optical clocks.

The effect of different nebulizers with and without intermittent positive pressure breathing on the absorption and metabolism of salbutamol

1 The absorption and metabolism of [(3)H]-salbutamol have been studied to assess whether intermittent positive pressure breathing (IPPB) or a particular nebulizer have any advantages in delivering bronchodilator drugs to asthmatic patients. 2 [(3)H]-salbutamol (10 mg) was given to asthmatic patients from either the Bird Mark 7 ventilator without intermittent positive pressure, the Bird micronebulizer attached to an electric air compressor, or the Wright's nebulizer attached to the same compressor. 3 All patients showed a high early plasma level of radioactivity due mainly to free salbutamol. This pattern suggests absorption from the lung and is similar to that seen after giving the drug from the Bird nebulizer using IPPB. 4 In all cases less than 20% of the original dose was absorbed by the patient. 5 Improvement in forced expiratory volume in one second (FEV(1)) was seen with all three treatments.

The clinical pharmacology of salmefamol

1 The absorption, excretion and metabolism of [(3)H]-salmefamol, a new sympathomimetic bronchodilator drug, have been studied in asthmatic patients. 2 Following oral administration of 1 or 2 mg to four patients the drug was well absorbed, peak plasma levels occurring from 0.6-2.0 h after administration. An improvement in forced expiratory volume in 1 s (FEV(1)) (ranging from 12-50% above baseline) was seen. 3 Following aerosol administration of 0.22-0.34 mg to four patients a rapid rise in FEV(1) was seen (range 26-117%). The plasma and urinary pictures following this route were similar to those seen after oral administration, suggesting that the majority of the dose was swallowed. 4 Very little free salmefamol was found in plasma or urine, the majority being present as metabolites. Urinary radioactivity was mainly present in the form of sulphate conjugates of at least two compounds, one of which was salmefamol. The other compound has not been identified but it is suggested that it may be an active metabolite.

The effect of prednisone treatment on the half-life of intravenous hydrocortisone

1 The half-life of hydrocortisone (cortisol) has been measured in six patients before and after a three-week course of prednisone given for asthma. 2 There was considerable variation in peak plasma level of cortisol both within and between patients, but on both occasions the plasma half-lives were the same. 3 It was concluded that short courses of prednisone have no effect on the handling of hydrocortisone.

Absorption of drugs by the lung

Ten patients undergoing diagnostic bronchoscopy had radioisotopically labelled drugs put directly into their bronchi; two received sodium cromoglycate, two salbutamol, three salmefamol and three rimiterol. All four drugs were rapidly absorbed but higher peak plasma levels per unit dose were seen with sodium cromoglycate and salbutamol than with the other two drugs. It is suggested that the lung metabolizes salmefamol and rimiterol but does not metabolize salbutamol or sodium cromoglycate.

Organization, expression and polymorphism of the human persyn gene

Persyn is a recently identified member of the synuclein family with a distinct pattern of expression during pre- and postnatal development of the mouse peripheral and central nervous systems. As with other synucleins, persyn is believed to be involved in the pathogenesis of human neurodegenerative diseases. However, in contrast to other synucleins, high levels of persyn mRNA expression were also found in advanced breast carcinomas, suggesting an involvement of the encoded protein in breast tumour progression. Here we have used an antibody specific to human persyn to demonstrate that the level of this protein is increased in ageing cerebral cortex and in breast tumours. We cloned, characterized and sequenced the human persyn genomic locus and localized it to the long arm of chromosome 10 in the q23.2-q23.3 region. Sequence information was used to search for specific mutations in the protein coding regions of persyn mRNA and the persyn gene in breast tumours and tumour cell lines. No tumour-specific mutations were found, but two linked polymorphisms in the coding region were detected, both in mRNA and exons III and IV of the gene. These results suggest that development of breast tumours correlates with overexpression of the wild-type persyn protein. Detailed characterization of the human persyn locus is important for further studies of the involvement of persyn in neurodegeneration and malignancy.

BRCA1: a review of structure and putative functions

BRCA1 is a complex gene implicated in familial breast and ovarian cancer. Although it is almost certainly a tumour suppressor, it is also essential for the normal growth and development of embryonic cells. BRCA1 is probably involved in DNA damage and repair, in cell cycle regulation, and in differentiation of cells. It remains to be established whether all these functions are subserved by single mechanism or pathway. Since the cloning of BRCA1 in 1994, much has been learned about the function of the gene. However, a great deal more still has to be uncovered. The size of the protein coded by the BRCA1 gene and the variety of transcripts argues for a complexity of function and regulation that will provide intellectual and technical challenges for years to come.

Presence of a heterozygous substitution and its relationship to DT-diaphorase activity

A point mutation in the mRNA of NADP(H): quinone oxidoreductase 1 (NQO1, DT-diaphorase) is believed to be responsible for reduced enzyme activity in the adenocarcinoma BE cell line. The present study examined nine cultured human non-cancerous fibroblast cell strains, five of which were from members of a single cancer-prone family, which demonstrated widely varying activity levels of DT-diaphorase (41 - 3462 nmol min-1 mg-1 protein), to determine if genetic alteration of the NQO1 or NOQ2 gene was involved in determining enzyme activity. All cell strains expressed NQO1 and NQO2 mRNA as measured by a quantitative polymerase chain reaction amplification technique. No relationship was found between the level of mRNA expressed and the enzyme activity in the cells. Sequencing of the entire complementary DNA from the cell strains revealed only a single base substitution at nucleotide 609 in one allele encoding NQO1 in every cell strain from members of the cancer-prone family, except for one cell strain which expressed only the T at nucleotide 609 in both alleles. Subsequent examination of genomic DNA from 44 individuals revealed that this base substitution is present in approximately 50% of the population. The presence of the T at nucleotide 609 in the NQO1 locus does not appear to be directly causal for altered DT-diaphorase activity.

Pharmacology of asthma treatment: an overview

The major advance in the last decade in treating asthma is the realisation that it is primarily an inflammatory process in the airways and not a bronchial smooth-muscle disease. Accordingly, much more emphasis is being placed on the early introduction of regular anti-inflammatory therapy, greatly facilitated by the development of inhaled steroid products. Despite this, inhaled beta 2-agonists remain the other major therapy in modern asthma treatment because of their ability to provide rapid relief from potentially life-threatening bronchoconstriction. At present, there is a tendency to avoid regular daily use of beta 2-agonists alone for persistent symptoms. Theophylline is still used, despite concern about its toxicity. However, it does have pharmacological effects in addition to bronchodilatation that may give it an additional therapeutic role in asthma therapy. It seems unlikely that the search for new single-mediator antagonists or synthesis inhibitors will result in the development of a new, effective asthma treatment.

Disposition of dothiepin after overdose: effects of repeated-dose activated charcoal

Although the tricyclic antidepressant dothiepin is often encountered in deliberate self-poisonings, there are no published studies of its disposition in overdose. In the present study, we have documented the plasma disposition of dothiepin and its major metabolites in eight overdose patients. All had high initial levels of dothiepin (819-3,851 micrograms/L), dothiepin-S-oxide (655-2,162 micrograms/L), nordothiepin (88-422 micrograms/L), and nordothiepin-S-oxide (176-530 micrograms/L) that were considerably above steady-state therapeutic concentrations. In three patients who received treatment with repeated-dose activated charcoal, dothiepin half-lives were 10.6, 12.5, and 13.1 h compared with the literature range of 18.5-24 h. All patients survived and none experienced any significant cardiovascular event despite exhibiting clinical signs of tricyclic antidepressant overdose. We suggest that repeated-dose activated charcoal treatment may decrease the dothiepin half-life after overdose.

Epithelium-derived inhibitory factor in human bronchus

The potencies of histamine and methacholine were significantly increased by approximately 2- and 5-fold respectively in human non-diseased isolated bronchi on removal of the epithelium. In contrast, no increases in spasmogen potency were observed following epithelium removal in bronchi obtained from a sample of asthmatic human lung. The failure of epithelium removal to increase asthmatic bronchial sensitivity to histamine may have been due to a reduction in the release of an epithelium-derived inhibitory factor (EpDIF) resulting from disease-induced epithelial damage. A co-axial bioassay system in which endothelium-denuded rat aorta was used as the assay tissue was used to detect the release of a vasorelaxant EpDIF from human bronchial tissue. Histamine (100 microM) and methacholine (25 microM), in the presence of indomethacin (5 microM), reduced phenylephrine-induced tone in endothelium-denuded rat aorta in co-axial assemblies by 75 +/- 11 and 67 +/- 9% respectively. Removal of the bronchial epithelium abolished these responses, indicating that they were mediated by an EpDIF. It is possible that human airway smooth muscle is sensitive to this vasorelaxant EpDIF and that the absence of the source of this factor following epithelium removal caused the increases in sensitivity to spasmogens. Alternatively, the human bronchial epithelium may also release an EpDIF selective for airway smooth muscle.

PAF receptors in guinea-pig and human lung

The autoradiographic distribution and density of specific binding sites for the PAF receptor antagonist [3H]-WEB 2086 was assessed in non-diseased and asthmatic human lung and in guinea-pig airway tissue. In general, only very low levels of specific binding were detected in these tissues with no evidence for PAF receptors in airway smooth muscle. Asthma does not appear to involve significantly increased airway PAF receptor expression.

Adrenoceptors in airway smooth muscle

This review examines the roles and functional significance of alpha and beta-adrenoceptor subtypes in airway smooth muscle, with emphasis on human airway function and the influence of asthma. Specifically, we have examined the distribution of beta-adrenoceptors in lung and the influence of age, the epithelium, respiratory viruses and inflammation associated with asthma on airway smooth muscle beta-adrenoceptor function. Sites of action, beta 2-selectivity, efficacy and tolerance are also examined in relation to the use of beta 2-agonists in man. In addition, alpha-adrenoceptor function in airway smooth muscle has been reviewed, with some emphasis on comparing observations made in airway smooth muscle with those in animal models.

Contractile effects and receptor distributions for endothelin-1 (ET-1) in human and animal airways

ET-1 caused concentration-dependent, sustained contraction of all airway preparations tested and was most potent in mouse trachea, with rat trachea, human bronchus and guinea-pig trachea approximately 5, 10 and 70 fold less sensitive respectively. Human non-asthmatic and asthmatic bronchi were approximately equi-sensitive to ET-1. Quantitative light microscopic autoradiography demonstrated high levels of specific [125I]-ET-1 binding sites in airway smooth muscle of rat trachea greater than human asthmatic bronchus = human non-asthmatic bronchus greater than mouse trachea much greater than guinea-pig trachea. High levels of specific ET-1 binding were also revealed in peripheral airways and in alveolar wall tissue in human, rat and mouse lung. In a limited sample of asthmatic airway smooth muscle ET-1 receptor function and density was not elevated.

Autoradiographic localization of beta-adrenoceptors in asthmatic human lung

The autoradiographic distribution and density of beta-adrenoceptors in human non-diseased and asthmatic bronchi were investigated using [125I]iodocyanopindolol (I-CYP). Analysis of the effects of the beta-adrenoceptor antagonists on I-CYP binding demonstrated that betaxolol (20 nM, beta 1-selective) had no significant effect on specific grain density in either nonasthmatic or asthmatic human bronchus, whereas ICI-118551 (20 nM, beta 2-selective) inhibited I-CYP binding by 85 +/- 9% and 89 +/- 3%, respectively. Thus, homogeneous populations of beta 2-adrenoceptors existed in bronchi from both sources. Large populations of beta-adrenoceptors were localized to the bronchial epithelium, submucosal glands, and airway smooth muscle. Asthmatic bronchial tissue featured epithelial damage with exfoliated cells associated with luminal mucus plugs. A thickened basement membrane and airway smooth muscle hyperplasia were also evident. High levels of specific I-CYP binding were also detected over asthmatic bronchial smooth muscle, as assessed by autoradiography and quantitation of specific grain densities. Isoproterenol and fenoterol were 10- and 13-fold less potent, respectively, in bronchi from asthmatic lung than in those from nonasthmatic lung. However, this attenuated responsiveness to beta-adrenoceptor agonists was not caused by reduced beta-adrenoceptor density in asthmatic airways. A defect may exist in the coupling between beta-adrenoceptors and postreceptor mechanisms in severely asthmatic lung.

Alpha 1-adrenoceptor function and autoradiographic distribution in human asthmatic lung

1. The autoradiographic distribution of alpha 1-adrenoceptors was investigated in non-diseased and asthmatic human lung by use of [3H]-prazosin (H-PZ). To validate binding and autoradiographic methods, H-PZ binding was also measured in rat heart. 2. Significant levels of specific H-PZ binding were detected in sections of rat heart. This binding was associated with a single class of non-interacting sites of high affinity (dissociation constant, Kd = 1.17 +/- 0.26 nM). The maximum binding capacity (Bmax) was 59.5 +/- 4.5 fmol mg-1 protein. 3. In sharp contrast, very low levels of specific H-PZ binding were found in both human nondiseased and asthmatic bronchus, although a high level of binding of [125I]-iodocyanopindolol (I-CYP, 50 pM) to beta-adrenoceptors was detected in these airways. Furthermore, very low levels of autoradiographic grains representing specific H-PZ binding were found in all airway structures in human non-diseased or asthmatic lung parenchyma. 4. Consistent with these data, the alpha-adrenoceptor agonist phenylephrine failed to induce significant increases in tone in bronchi isolated from either non-diseased or asthmatic human lung. Results indicate that asthma does not involve significant increases in airway alpha 1-adrenoceptor function.

Co-axial bioassay of a smooth muscle relaxant factor released from guinea-pig tracheal epithelium

1. The ability of guinea-pig trachea to release an epithelium-derived relaxant factor (EpDRF) was assessed in a co-axial bioassay system. 2. Histamine (100 microM) and methacholine (25 microM) caused endothelium-dependent relaxation of rat isolated aorta, presumably via the release of endothelium-derived relaxant factor (EDRF). In contrast, endothelium-denuded rat aorta did not relax in response to these agents. 3. EDRF release was detected in response to methacholine in a co-axial bioassay system, consisting of intact rabbit aorta tube (EDRF donor) and endothelium-denuded rat aorta strip (assay preparation). These results indicated the transfer of EDRF from a donor to an assay preparation, thereby validating the co-axial bioassay method. 4. Substitution of endothelium-intact rabbit aorta tube by epithelium-intact guinea-pig tracheal tube tissue in co-axial assemblies, still allowed the assay preparation to relax in response to histamine or methacholine. Removal of the intact tracheal tube from the system, or removal of the epithelium from the donor tracheal tube in co-axial preparations, abolished such relaxant responses. These observations are consistent with histamine- or methacholine-induced release of an epithelium-derived relaxant factor (EpDRF) from the trachea. 5. In the co-axial assembly comprising intact guinea-pig trachea and endothelium-denuded rat aorta, histamine and methacholine produced concentration-dependent, EpDRF-induced aortic relaxation. Mean concentrations of histamine and methacholine producing 50% of the maximum relaxation (EC50) were 39.8 microM and 2.7 microM respectively. Histamine-induced relaxation was inhibited in the presence of mepyramine (2 microM) and responses to methacholine were inhibited by atropine (0.1 microM). 6. Methylene blue (50 microM) had no effect on such relaxant responses, indicating that EpDRF does not activate guanylate cyclase. Furthermore, the cyclo-oxygenase inhibitor indomethacin (5 microM), the cyclo-oxygenase/lipoxygenase inhibitor BW 755C (150 microM) and the leukotriene receptor antagonist FPL 55712 (10 microM) each failed significantly to alter EpDRF-mediated relaxation of vascular smooth muscle suggesting that EpDRF is not a prostanoid. Platelet activating factor (Pat) failed to cause relaxation of endothelium-denuded rat aorta, indicating that this mediator was also not EpDRF. 7. EpDRF was also released from human bronchial segments. 8. This study provides direct evidence for the release of an EpDRF from non-diseased airway tissue and further suggests that healthy airway reactivity to spasmogens is modulated by the release of an endogenous protective, spasmolytic substance. The bronchial hyperreactivity of asthma may be partly caused by attenuated production of such an inhibitory signal.

Beta-adrenoceptor desensitization in guinea-pig isolated trachea

Exposure to (-)-isoprenaline (25 microM, 1 h) caused a stereoselective, time and concentration-related decrease in smooth muscle beta 2-adrenoceptor function in guinea-pig trachea. Furthermore, tracheal relaxant responsiveness to the beta-adrenoceptor agonists (+/-)-fenoterol and (-)-noradrenaline was reduced, while that to theophylline and nitroprusside was unaffected. Responsiveness to forskolin was marginally but significantly reduced. Indomethacin, a cyclooxygenase inhibitor and mepacrine, an inhibitor of phospholipid turnover, had no significant effect on the extent of isoprenaline-induced desensitization. Conversely, cortisol (25 microM) significantly reduced desensitization and enhanced the rate of spontaneous recovery of responsiveness to isoprenaline. Desensitization was not accompanied by a reduction in the density of beta-adrenoceptors in the trachea, as assessed by binding and light microscopic autoradiography using [125I]iodocyanopindolol [( 125I]CYP). Thus, desensitization was probably caused primarily by beta-adrenoceptor/adenyl cyclase uncoupling. This model may be useful in investigations of the effect of glucocorticoids on the beta-adrenoceptor dysfunction recognized in severe asthma.

An overview of the current status of the drug therapy of asthma

The importance of inflammation as the central lesion in asthma is being increasingly recognised and it is proposed that the emphasis of therapy should be altered from simply treating symptoms, to trying to control inflammation at an early stage of the disease. A "tight control" treatment program to achieve this is outlined. Treatment regimes for asthma may therefore need to be re-assessed, although the most commonly used drugs (beta 2-adrenoceptor agonists, theophylline, corticosteroids and cromoglycate) are effective if used properly. For the majority of patients management is grossly inadequate in terms of diagnosis, assessment of disease severity and treatment. The death rate from asthma still remains unacceptably high and some strategies are outlined for the identification of patients at risk and the improvement of their management. This overview considers four central issues: (1) the lesions that should be the target for drug treatment; (2) an outline of the available drug treatment; (3) the aims of treatment and (4) the success of drug treatment in terms of morbidity and mortality.

In vitro responsiveness of human asthmatic bronchus to carbachol, histamine, beta-adrenoceptor agonists and theophylline

Responses of human bronchial strip preparations to contractile and relaxant agonists were measured in preparations from non-diseased and from asthmatic lung obtained 3-15 h post-mortem. The potencies of carbachol and histamine were approximately two times less in asthmatic than in non-diseased bronchi. This was statistically significant for carbachol (P less than 0.05), but not for histamine (P greater than 0.05). These results clearly indicate that the bronchial hyperreactivity to airway spasmogens observed in asthma is exclusively an in vivo phenomenon not involving increasing sensitivity of bronchial smooth muscle. The potencies of the beta-adrenoceptor agonists isoprenaline, fenoterol and terbutaline were significantly reduced by 4-5 fold in asthmatic bronchi compared with non-diseased airways. In contrast, theophylline was equipotent in the two populations of airway preparations. Thus, it appears that severe asthma is associated with decreased bronchial smooth muscle beta 2-adrenoceptor function.

An ultrastructural study of mast cells in the alveolar wall of normal and asthmatic lung

Specimens of normal and asthmatic lungs were studied at the electron microscopic level and the frequency and ultrastructural features of mast cells and their granules within the alveolar wall were assessed with morphometric techniques. The numerical density of mast cells per square millimetre of alveolar wall was 299 (SD = 258) in normal and 366 (SD = 260) in asthmatic lung. The mean area of the mast cell nucleated profile was 25.7 microns2 (SD = 6.3) in normal lung and 29.8 (SD = 6.2) in asthmatic. The average number of secretory granules per single mast cell nucleated profile was 55 (SD = 13) in normal lung and 60 (SD = 12) in asthmatic lung. The diameter of the individual secretory granule was 338.9 nm (SD = 42.6) in normal and 345.6 (SD = 47.7) in asthmatic lung. The volume density of secretory granules in normal and asthmatic lung was 6.31 microns3 and 5.81 microns3, respectively. The mean diameter of the individual subunit ('scroll') inside the secretory granule was 88.8 nm for both normal and asthmatic lung. In normal lung 64.2% of granules were of 'scroll' and 'combined' type, and 35.8% of granules were 'particulate' or 'empty'. In specimens from asthmatic patients 40.3% of granules had 'scroll' or 'combined' structures and 59.7% were 'particulate' or 'empty'. Our data suggest that there is no difference between the number of mast cells in normal and asthmatic lung. However, in pulmonary mast cells from asthmatic lung, degranulation is more common than in normal lung.

Adverse reactions to beta 2-agonist bronchodilators

Beta 2-Agonists are safe and effective bronchodilator drugs. Their major adverse effects of skeletal muscle tremor, tachycardia and various metabolic effects are mediated by beta-adrenoceptor stimulation and are reversible. Skeletal muscle tremor is the most frequent dose-limiting side effect. It may be reduced by commencing treatment with a low dose and if it persists another beta 2-agonist may be tried. Other side effects such as cardiac arrhythmias and reduction in PaO2 are a serious potential problem in some susceptible asthmatics. However, they are infrequent or of a mild degree and are generally outweighed by the good control of asthma produced by beta 2-agonists. Side effects from beta 2-agonist therapy can be minimised by use of the inhaled route which selectively delivers the drug to the airways. Furthermore, selective tolerance develops to their side effects. The dose of a beta 2-agonist should be assessed on the basis of therapeutic effect and the level of tolerance to its side effects. Recommended doses of beta 2-agonists used for long term therapy do not cause clinically significant desensitisation of airway beta-adrenoceptors, although this may become a relevant problem in patients who are regularly receiving very high doses. Intravenous beta 2-agonists have a place in the treatment of severe asthma not responding to nebuliser therapy. In this life-threatening situation with severe airflow obstruction, monitoring of heart rate, PaO2, plasma potassium and the electrocardiogram should be mandatory and supplemental oxygen given so that serious adverse effects are presented.

Autoradiographic localization of beta-adrenoceptors in pig lung using [125I]-iodocyanopindolol

The binding of the beta-adrenoceptor radioligand [125I]-iodocyanopindolol (I-CYP) has been studied in pig lung parenchyma and the distribution of binding sites visualised by light microscopic autoradiography. I-CYP binding was saturable (maximum binding capacity Bmax = 51 +/- 3 fmol mg-1 protein), involving sites with high affinity (dissociation constant KD = 73 +/- 10 pM). Specific I-CYP binding was displaceable both by beta-adrenoceptor agonists ((-)-isoprenaline greater than (-)-adrenaline greater than (+/-)-fenoterol greater than (-)-noradrenaline greater than (+)-isoprenaline greater than (+/-)-RO363) and antagonists ((+/-)-propranolol greater than ICI-118551 greater than atenolol), indicating a predominance of beta 2-adrenoceptors. Further analysis showed that displacement data for the beta 1-selective antagonist atenolol and the beta 2-selective antagonist ICI-118551 were fitted best to a 2 binding site model and that both beta 1- and beta 2-adrenoceptors were present in pig lung in the ratio 28:72 respectively. Autoradiographic grains were localized over tissue and were most dense over alveolar walls greater than vascular endothelium greater than vascular smooth muscle greater than bronchial smooth muscle = bronchial epithelium. Atenolol (10(-5) M) caused a 31% reduction in specific grain density over alveolar wall tissue, while a 10 fold lower concentration of ICI-118551 (10(-6) M) caused a 50% decrease. These results are consistent with binding data in pig lung parenchyma demonstrating a mixed population of beta-adrenoceptors with a predominance of the beta 2 subtype. 6 It is possible that the previously described relaxant responses of the pig lung parenchyma strip to beta-agonists, mediated via beta 2-adrenoceptors, resulted from the sum of reactivities in airway and vascular smooth muscle together with relaxation of alveolar interstitial cells.

Autoradiographic localisation of ascorbic acid-dependent binding sites for [125I]iodocyanopindolol in guinea-pig trachea

Light microscopic autoradiography showed that the supposedly beta-adrenoceptor-selective radioligand [125I]iodocyanopindolol (I-CYP) bound to sites in both the guinea-pig tracheal epithelium and smooth muscle that were sensitive to propranolol and isoprenaline. Low levels of binding were associated with sub-epithelial mucosal cells. Ascorbic acid caused a concentration-related increase in total I-CYP binding which was predominantly associated with the sub-epithelial mucosa, was not inhibited by propranolol, and was thus not associated with beta-adrenoceptors.

Beta agonist-induced desensitization in pig bronchus

Pretreatment of pig isolated bronchial preparations with isoproterenol (Iso) caused a time and concentration-related decrease in both the relaxant potency (pD2) and maximal relaxant effect (Emax) of Iso. Exposure to Iso (5 microM) caused an apparent reduction in the Iso pD2 at 6 hr of approximately 74-fold with a concomitant decrease in Iso Emax from 108 +/- 2 (n = 43) to 55 +/- 6% (n = 11). Responsiveness to the relaxant effects of Iso recovered spontaneously but slowly, being still incomplete 4 hr after desensitization with Iso (1 microM, 3 hr). Responsiveness to norepinephrine and fenoterol was also reduced markedly after exposure to Iso (5 microM), although the relaxant effects of the nonbeta agonists theophylline and forskolin were not reduced. Indeed, the potency of forskolin, was increased 4-fold. The beta antagonists propranolol (nonselective) and atenolol (beta-1 selective) protected bronchi from Iso-induced desensitization, whereas ICI-118551 (beta-2 selective) did not. Furthermore, the dextro (+)-isomer of Iso was virtually inactive as a desensitizing agent. Pretreatment with norepinephrine and fenoterol also decreased the relaxant effects of Iso, although they were at least 100 times less potent than Iso in desensitizing pig bronchi. These results indicate that desensitization was specifically mediated via beta-1 adrenoceptors which predominate in pig bronchus. Alpha adrenoceptor activity mediating increased bronchial tone was apparent in Iso-desensitized bronchi but not in nondesensitized preparations even in the presence of beta adrenoceptor blockade. Neither the cyclooxygenase inhibitor indomethacin, nor the phospholipase A2 inhibitor mepacrine had any significant effect on the extent of Iso-induced desensitization in pig bronchus.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of the epithelium on responsiveness of guinea-pig isolated trachea to contractile and relaxant agonists

The potency (pD2) and maximal contractile effect (Emax) of histamine, acetylcholine, carbachol and K+ were assessed from cumulative concentration-effect curves in guinea-pig isolated tracheal ring preparations with and without an intact epithelium. Estimates of Emax were not significantly different in epithelium-denuded preparations compared with those measured in intact preparations; pD2 values for acetylcholine, carbachol and K+ were not significantly altered. In contrast, the potency of histamine was significantly increased by about 4 fold in preparations devoid of epithelial cells. Estimates of potency and Emax were also determined for the smooth muscle relaxants isoprenaline, forskolin and theophylline (which increase intracellular cyclic AMP) and for nitroglycerin (which increases cyclic GMP) in both intact and epithelium-stripped tracheal rings. The pD2 values for these relaxants were not significantly altered by the removal of the epithelium. However, with the exception of nitroglycerin, Emax values for these relaxants were significantly lower in stripped than in intact tracheal rings that had been maximally precontracted with carbachol. The autoradiographic localisation of binding sites for the non-selective beta-adrenoceptor ligand [125I]-iodocyanopindolol (I-CYP) showed that the epithelium of the guinea-pig trachea had a 75 +/- 16% greater density of beta-adrenoceptors than the smooth muscle. Removing the epithelium did not significantly alter either the density of smooth muscle binding sites or the affinity of I-CYP binding. It was concluded that the reduced functional response of guinea-pig trachea to isoprenaline was probably not due to smooth muscle beta-adrenoceptor dysfunction. Results indicate that the epithelium plays an important role in the modulation of responsiveness of guinea-pig trachea to histamine and relaxants that mediate their effects by selectively increasing intracellular cyclic AMP levels.

Experimental testing of Mackay's model for functional antagonism in the isolated costo-uterus of the rat

Several key predictions of a recently developed model for functional antagonism (Mackay, 1981) were experimentally tested using the rat isolated costo-uterine preparation. In the presence of the functional antagonist fenoterol (Fen), the functional constants (KAF) for carbachol and oxotremorine (Oxo) were respectively 9.9 and 3.4 fold greater than their corresponding affinity constants (KA). According to Mackay's model for functional antagonism, the higher KAF/KA ratio for carbachol indicates that this cholinoceptor agonist has a greater efficacy than Oxo. This was confirmed by using conventional pharmacological methods. As predicted from the model of functional antagonism, the plot of KAF/KA-1 against the fraction of cholinoceptors not irreversibly blocked by phenoxybenzamine (Pbz) was linear for both carbachol and Oxo and the lines of best fit crossed the axes at a point not significantly different from the origin. The value of 4.6 for the relative efficacy of carbachol to Oxo estimated from functional antagonism studies was comparable to the value of 5.6 calculated using the method of irreversible antagonism proposed by Furchgott (1966).

Classification of beta-adrenoceptors in human isolated bronchus

(+/-)-Isoprenaline (Iso), (-)-adrenaline (Ad), (-)-noradrenaline (NA), (+/-)-phenylephrine (Phe) and the beta 2-selective adrenoceptor agonist (+/-)-fenoterol (Fen) caused a concentration-dependent relaxation of human isolated bronchial preparations. Iso, Ad and NA caused complete relaxation of both spontaneous and carbachol-induced bronchial tone. Fen, which was only tested in preparations where tone was induced with carbachol, also caused complete relaxation. However, Phe was a partial agonist in all preparations tested. When relaxation responses to these amines were calculated as a % of their maximal effects, comparison of EC50 values showed that the order of potency was Iso greater than Ad = Fen greater than NA greater than Phe (92:27:25:1:0.2) in preparations with carbachol-induced tone and Iso greater than Ad greater than NA greater than Phe (112:38:1:0.3) in preparations with spontaneous tone. pA2 values determined for the beta-adrenoceptor antagonists propranolol (non-selective), atenolol (beta-selective) and ICI-118, 551 (beta 2-selective), using Iso as an agonist were, 9.3, 5.3 and 9.1 respectively. These results indicate that beta 2-adrenoceptors mediate relaxation of human isolated bronchus to sympathomimetic amines in preparations obtained 4-14 h post-mortem from non-diseased lung. alpha-Adrenoceptors were apparently sparse or absent in this tissue.

Effects of adrenaline and carbachol on the morphology of alveolar contractile cells in the lung of the toad (Bufo marinus)

Smooth muscle-like interstitial cells in toad (Bufo marinus) lung strips were examined by light and electron microscopy and subjected to morphometric analysis in an attempt to assess the effect of spasmogenic and relaxant agonists on contractile cells in peripheral airways. Carbachol (12.8 microM) caused a 43.6% reduction in contractile cell length compared to control, while adrenaline (100 microM) caused a 21.3% increase. The mean transverse and longitudinal-sectional area and perimeter of cell profiles were significantly greater in carbachol treated preparations than in control. In tissue that had relaxed after exposure to adrenaline, the mean area of longitudinally sectioned cells and the perimeter of cell profiles were significantly reduced.

Ethanol- and isoprenaline-induced responses in pig parenchymal lung tissue

Ethanol (8.7-34.8 mM; 0.5-0.20% v/v) had no significant effect on spontaneously developed tension in pig lung parenchyma strips, although higher cumulative concentrations caused relaxation (at 34.8-174 mM) and contraction (at 348-1392 mM). Ethanol-induced effects were not caused by activation of adrenoceptors or of cholinoceptors, since blockade of these receptors did not alter those effects. Single low concentrations of ethanol (8.7-34.8 mM) which can occur in-vivo in man, caused increases in the relaxant potency of isoprenaline in pig lung strips, although the sizes of these increases varied widely. In addition, ethanol-induced potentiation of isoprenaline was not concentration-related. This effect was not caused by inhibition of isoprenaline uptake since [3H]isoprenaline transport was found not to be significantly altered in the presence of ethanol (8.7-34.8 mM).

Effect of hypothermia on beta 1-adrenoceptor-mediated relaxation of pig bronchus

The relaxant potencies of (+/-)-isoprenaline and of (-)-noradrenaline (NA) in the pig isolated bronchus were increased 5.4 and 3.1 fold respectively by lowering the organ bath temperature from 37 degrees C to 27 degrees C, whereas the potencies of the non-catecholamine beta-adrenoceptor agonists fenoterol and orciprenaline were not significantly changed. At 37 degrees C, the catechol-O-methyl transferase (COMT) inhibitor U-0521 (30 microM), caused a 7.2 fold increase in the potency of isoprenaline but had no effect on the potency of fenoterol. At 27 degrees C the potency of isoprenaline was similar in the absence or presence of U-0521 (30 microM). Furthermore, in bronchi where extraneuronal uptake was inhibited by phenoxybenzamine, the potency of NA was not significantly altered by reducing bathing temperature from 37 degrees C to 27 degrees C. These results suggest that the hypothermic potentiation of isoprenaline in pig bronchus resulted from inhibition of COMT or of access to COMT, rather than from sensitization of beta 1-adrenoceptors.

Correlations between pharmacological responses and structure of human lung parenchyma strips

Correlations were sought between responses of human lung parenchyma strip to 5-hydroxytryptamine (5-HT) and (-)-noradrenaline (NA) and the proportions of the three major, potentially contractile components within the strip, namely smooth muscle in airways proximal to alveolar ducts, vascular smooth muscle and contractile cells in alveolar septa. After the isometric measurement of responses to 5-HT or to NA, lung strips were processed for stereological examination at the light microscopic level. On average, approximately 46% of the total volume of the lung strip was tissue and the remainder was air space. Tissue contained blood vessels (16.8%), airways proximal to alveolar ducts (4.8%) and alveolar parenchyma (78.4%). Human lung parenchyma strips relaxed, contracted or failed to respond to 5-HT or NA. Results indicated that these agonists caused simultaneous contraction of blood vessels and relaxation of airways proximal to alveolar ducts. The size and type of responses to 5-HT or NA was significantly correlated with the ratio of the volume of blood vessels and larger airways. Conversely, the proportion of alveolar tissue in lung strips was not significantly correlated with responses to 5-HT or NA.

Evaluation of ketotifen (HC20-511) in bronchial asthma

Ketotifen 1 mg b.d. (oral) and sodium cromoglycate 20 mg q.i.d. (inhalation) were compared in a double-blind crossover trial in 43 asthmatic outpatients. Comparison of diary card scores and pulmonary function tests showed significant improvement over a 12 week period on each drug. Comparison of the diary card scores and pulmonary function tests showed no significant difference between the drugs after 12 weeks of treatment. Twenty-six patients experienced sedation and/or lethargy whilst on ketotifen and 11 patients had similar side effects whilst on cromoglycate. Physician preferences based on diary card and pulmonary function data showed an approximately equal number of preferences for each medication and also a small group of patients in which no preference could be made. The present trial suggests that both ketotifen and cromoglycate are effective in the management of outpatient asthma. When all the patients are considered as a group no distinction can be made between the two drugs; on the basis of physician assessment of each patient, it appears that some patients may do better on ketotifen and others on cromoglycate.

Classification of beta-adrenoceptors in isolated bronchus of the pig

1 (+/-)-Isoprenaline (Iso), (-)-adrenaline (Ad), (-)-noradrenaline (NA), the beta 2-selective adrenoceptor agonist (+/-)-fenoterol (Fen) and the beta 1-selective adrenoceptor agonist (+/-)-RO363 caused concentration-dependent relaxation of preparations of pig bronchus pre-contracted with carbachol 40-ng/ml (0.22 microM). Iso, Ad, NA and Fen caused complete relaxation of carbachol-induced tone, but RO363 caused relaxation equivalent to only 59% of the maximal response to Iso. 2 When relaxation responses to these amines were plotted as a % of their maximal effects, comparison of EC50 values showed that the order of potency was RO363 greater than Iso greater than NA greater than Fen greater than Ad (14.4:4.6:1:0.4:0.3). 3 pA2 values determined for the beta-adrenoceptor antagonists propranolol (non-selective) and atenolol (beta 1-selective), or the partial agonist salbutamol (beta 2-selective) using Iso as agonist were 8.3, 7.3 and 4.4 respectively. The pA2 value for atenolol using RO363 as the agonist was 7.6. 4 These results indicate that porcine bronchus contains a homogeneous population of beta 1-adrenoceptors.

Effect of steroids on beta-adrenoceptor-mediated relaxation of pig bronchus

1--Progesterone, testosterone (40 microM), cortisol and cortisol hemisuccinate (80 microM) caused 6-8 fold potentiations of (+/-)-isoprenaline (Iso)-induced relaxations of pig bronchus while several other steroids caused smaller potentiations or had no effect. 2--17 beta-Oestradiol (40 microM) increased the potency of Iso, (-)-adrenaline (Adr) and (-)-noradrenaline (NA) by 10.6, 2.3 and 2.6 fold respectively but had no significant effect on the potency of fenoterol (Fen). 3--Inhibition of catechol-O-methyl transferase (COMT) with U-0521 (30 microM) caused a 6 fold increase in the potency of Iso but failed to alter the potency of Adr, NA or Fen. The extraneuronal uptake inhibitor normetanephrine (50 microM) caused significant 2 fold increases in the potency of Iso and Adr but did not potentiate the responses to NA or Fen. 4--In preparations where the potency of Iso had already been increased by U-0521 (30 microM) or by normetanephrine, 17 beta-oestradiol produced no significant further increase in potency. These results indicate that steroid-induced increases in the potency of catecholamines in pig bronchus can be explained in terms of inhibition of COMT or extraneuronal uptake or both.

A pharmacological and ultrastructural study of alveolar contractile tissue in toad (Bu fo marinus) lung

The structure of the wall of the lung from the toad (Bufo marinus) has been examined using scanning and transmission electron microscopy and the presence of smooth muscle cells in the septal-alveolar walls detected. Responses of toad isolated lung parenchyma strip to agonists causing relaxation and contraction were measured and the potencies of adrenoceptor and 5-hydroxytryptamine receptor antagonists were determined. Results indicated the presence of populations of alpha- and beta-adrenoceptors in toad lung alveoli, both of which mediate relaxation responses. Stimulation of both alpha- and beta-adrenoceptors was required to cause complete relaxation. 5-Hydroxytryptamine also caused complete relaxation. A population of alpha-adrenoceptors mediating contraction may also exist in pulmonary vascular and or septal edge smooth muscle.

Catecholamine transport in isolated lung parenchyma of pig

1 Lung parenchyma strips of the pig incubated at 37 degrees C with [(3)H]-(-)-noradrenaline ([(3)H]-NA) or [(3)H]-(+/-)-isoprenaline ([(3)H]-Iso), accumulated radioactivity via saturable, high affinity uptake processes. Apparent saturation constants (K(m)) for [(3)H]-NA and [(3)H]-Iso were 1.34 x 10(-6) M and 1.63 x 10(-6) M respectively, while apparent transport maxima (V(max)) were 4.86 and 1.63 x 10(-9) mol min(-1) g(-1) respectively.2 Cellular accumulation of radioactivity from radiolabelled catecholamines was greatly reduced by lowering the temperature to 7 degrees C, pretreatment with ouabain (100 muM), phentolamine (15 muM) or phenoxybenzamine (80 muM). However, accumulation of radioactivity derived from ((3)H]-NA was inhibited selectively by cocaine (10 muM) and desipramine (1 muM), while normetanephrine (80 muM) and 3-O-methylisoprenaline (50 muM) caused much greater reductions in cellular radioactivity from [(3)H]-Iso than from ((3)H]-NA. Taken together with information from kinetic studies, the results indicate that these amines are transported by separate uptake processes.3 Cocaine (50 muM) which selectively reduced [(3)H]-NA transport, had no significant effect on the sensitivity (EC(50)) of isolated parenchyma lung strips of the pig to the contractile effects of cumulative concentrations of NA. The catechol-O-methyl transferase (COMT) inhibitor, U-0521 (60 muM), also failed to alter the potency of NA, while normetanephrine (80 muM) caused a 2 fold decrease in potency.4 Phentolamine (15 muM), which reduced the cellular accumulation of radioactivity derived from [(3)H]-Iso by 64%, caused a small potentiation of Iso-induced relaxations of porcine lung strips. Normetanephrine (80 muM) and 3-O-methylisoprenaline (50 muM), which also depressed the accumulation of cellular radioactivity from [(3)H]-Iso by > 50%, caused rightward shifts in Iso concentration-effect curves as a result of beta-adrenoceptor blockade. In sharp contrast, cortisol (80 muM) and U-0521 (60 muM), which caused smaller reductions in the cellular accumulation of radioactivity derived from [(3)H]-Iso, both caused an approximately 9 fold potentiation of responses to Iso in isolated lung strips.5 The results indicate that the major sites of uptake and metabolism of NA in porcine parenchyma strip are remote from alpha-adrenoceptors mediating NA-induced contraction. Similarly, some major sites of uptake of Iso are remote from beta-adrenoceptors mediating Iso-induced relaxation. However, beta-adrenoceptors are apparently in close proximity to a compartment containing COMT activity.

A comparative study of beta-adrenoceptors in human and porcine lung parenchyma strip

1. Responses to (+/-)-isoprenaline (Iso), (-)-adrenaline (Adr) and (-)-noradrenaline (NA) were compared in isolated preparations of human and porcine lung parenchyma strip. 2. The order of relaxant potencies of these catecholamines in both human and porcine lung parenchyma was Iso greater than Adr greater than NA (1:0.24:0.01, human; 1:0.21:0.01.pig). These results suggest that beta 2-adrenoceptors predominate in both types of lung parenchyma strip. 3. pA2 values for the beta-adrenoceptor antagonist, propranolol (non-selective), with Iso as the agonist, in human and porcine lung strips were 7.84 and 7.83 respectively and for atenolol were 6.50 and 5.35 respectively. Taken as a whole results indicate the existence of an apparently homogeneous population of beta 2-adrenoceptors in porcine parenchyma strip, while both beta 1 and beta 2-adrenoceptors were revealed in human lung parenchyma.