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D M Geddes

Publications and source records attributed to D M Geddes.

At least 19 recordsLinked to original sources
PubMed1992

Cystic fibrosis in the mouse by targeted insertional mutagenesis.

Cystic fibrosis is a fatal genetic disorder which afflicts 50,000 people worldwide. A viable animal model would be invaluable for investigating and combating this disease. The mouse cystic fibrosis transmembrane conductance regulator gene was disrupted in embryonal stem cells using an insertional gene targeting vector. Germ-line chimaeras were derived and the offspring of heterozygous crosses studied. These homozygous mutant mice survive beyond weaning. In vivo electrophysiology demonstrates the predicted defect in chloride ion transport in these mice and can distinguish between each genotype. Histological analysis detects important hallmarks of human disease pathology, including abnormalities of the colon, lung and vas deferens. This insertional mouse mutation provides a valid model system for the development and testing of therapies for cystic fibrosis patients.

Animals↗
PubMed1992

Ion transport characteristics of the murine trachea and caecum.

1. The basic defect in cystic fibrosis relates to abnormalities of ion transport in affected tissues, such as the respiratory and gastrointestinal tracts. The identification of the cystic fibrosis gene has enabled studies on the production of a cystic fibrosis transgenic mouse to be undertaken. Knowledge of normal ion transport will be necessary for the validation of any such animal model. We have therefore characterized selected responses of the murine trachea and caecum mounted in 'mini' Ussing chambers under open-circuit conditions. 2. Basal values for the trachea were: potential difference, 1.1 mV (SEM 0.2; n = 18); equivalent short-circuit current, 20.4 microA/cm2 (3.6); conductance, 18.2 mS/cm2 (1.7). Corresponding values for the caecum were: potential difference, 0.7 mV (0.1; n = 18); equivalent short-circuit current, 11.0 microA/cm2 (1.6); conductance, 14.5 mS/cm2 (1.4). 3. Amiloride (10 mumol/l) produced a significant (P less than 0.001) fall in potential difference of 43.0% (5.7) in the trachea, but had no significant effect in the caecum. 4. Subsequently, one of three protocols was used to assess the capacity of either tissue for chloride secretion. Addition of a combination of forskolin (1 mumol/l) and zardaverine (10 mumol/l) produced rises in the potential difference of 873% (509) in the trachea and 399% (202) in the caecum. Both A23187 (10 mumol/l) and phorbol dibutyrate (10 nmol/l) increased tracheal potential difference by 350% (182) and 147% (47), respectively. Neither had a significant effect in the caecum. 5. Subsequent addition of bumetanide caused a fall in the stimulated potential difference of between 39.8% and 71.7%, depending on secretagogue and tissue type.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride↗
PubMed1992

Effects of 5-hydroxytryptamine and 5-hydroxytryptamine receptor agonists on ion transport across mammalian airway epithelia.

1. 5-Hydroxytryptamine has been suggested as a candidate for an endogenous inhibitor of airway sodium transport. Amiloride, an inhibitor of epithelial sodium channels, has therapeutic potential in disorders of airway ion transport such as cystic fibrosis, but its duration of action in vivo is short. 5-Hydroxytryptamine and related compounds have been studied to investigate whether any might be a useful alternative to amiloride for clinical use, and to further assess the possible physiological role of 5-hydroxytryptamine in the regulation of airway ion transport. 2. Sheep tracheal epithelium was mounted in Ussing chambers under short-circuit conditions. Mucosal application of 5-hydroxytryptamine resulted in an immediate, reversible, concentration-related decrease in the short-circuit current, maximal with 38% inhibition of the short-circuit current at 25 mmol/l. This response was completely inhibited by pretreatment of tissues with mucosal amiloride (100 mumol/l). These features are consistent with a direct effect of 5-hydroxytryptamine on amiloride-sensitive sodium channels. Similar results were obtained in a limited number of studies using human bronchial epithelium. 3. The effects of mucosal addition of a range of 5-hydroxytryptamine agonists were studied to determine if any was a more potent blocker of amiloride-sensitive sodium transport than 5-hydroxytryptamine. The 5-HT3 agonist 2-methyl-5-hydroxytryptamine had no effect on the short-circuit current at concentrations of up to 5 mmol/l. The 5-HT1D agonist sumatriptan had no effect at concentrations below 5 mmol/l and at 5 mmol/l had only a transient effect.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1992

Second-messenger regulation of sodium transport in mammalian airway epithelia.

1. Sodium absorption is the dominant ion transport process in conducting airways and is a major factor regulating the composition of airway surface liquid. However, little is known about the control of airway sodium transport by intracellular regulatory pathways. 2. In sheep tracheae and human bronchi mounted in Ussing chambers under short circuit conditions, the sodium current can be isolated by pretreating tissues with acetazolamide (100 microM) to inhibit bicarbonate secretion, bumetanide (100 microM) to inhibit chloride secretion and phloridzin (200 microM) to inhibit sodium-glucose cotransport. This sodium current consists of amiloride-sensitive (57%) and amiloride-insensitive (43%) components. 3. The regulation of the isolated sodium current by three second messenger pathways was studied using the calcium ionophore A23187 to elevate intracellular calcium, a combination of forskolin and the phosphodiesterase inhibitor zardaverine to elevate intracellular cyclic AMP, and the phorbol ester 12,13-phorbol dibutyrate (PDB) to stimulate protein kinase C. 4. In sheep trachea, A23187 produces a dose-related inhibition of the sodium current with maximal effect (38% of ISC) at 10 microM and IC50 1 microM. This response affects both the amiloride-sensitive and insensitive components of the sodium current and is not altered by prior stimulation of protein kinase C or elevation of intracellular cyclic AMP. In human bronchi, A23187 (10 microM) produced a significantly greater inhibition of ISC (68%), a response which was unaffected by prior treatment with PDB or forskolin-zardaverine. 5. In sheep trachea, stimulation of protein kinase C with PDB produced a dose-related inhibition of ISC maximal (56% of ISC) at 50 nM (IC50 7 nM). This response was abolished by amiloride (100 microM) pretreatment suggesting a selective effect on the amiloride-sensitive component of the sodium current. The response was not altered by prior elevation of intracellular calcium or cyclic AMP. PDB (10 nM) caused a similar inhibition of ISC in human bronchi (43%). The effect of PKC stimulation following pretreatment with A23187 was diminished in human bronchi. Elevating intracellular cyclic AMP did not alter this response. 6. Addition of forskolin (1 microM) together with the phosphodiesterase inhibitor zardaverine (100 microM) produced a mean 35-fold increase in intracellular cyclic AMP in sheep trachea. This was associated with a small, but significant, 6% transient increase in ISC followed by a significant 4% fall. Neither effect could be abolished by amiloride pretreatment. In human bronchi, a small decrease in ISC which could not be distinguished from that occurring in controls was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Bioelectric properties of cystic fibrosis airways obtained at heart-lung transplantation.

BACKGROUND: The basic defect in cystic fibrosis centres on abnormal ion transport in affected tissues such as the respiratory tract. Heart-lung transplantation provides a limited supply of native lower airways from these patients. The feasibility of in vitro studies of bioelectric properties and ion fluxes in lower airways, obtained at heart-lung transplantation from patients with cystic fibrosis, has been assessed. Comparison was made with airways from patients without cystic fibrosis. METHODS AND RESULTS: Tissue segments were mounted in Ussing chambers under open circuit conditions. The basal potential difference in tissues from nine patients with cystic fibrosis was -3.6 mV (SE 0.3 mV), not different from tissues from 12 patients without cystic fibrosis of -3.6 mV (0.5 mV). Amiloride (10 microM) caused a significantly greater fall in potential difference in bronchi from patients with cystic fibrosis (83.5% (SE 2.9%)) than in those from controls (55.1% (7.1%)). Isoprenaline (100 microM) produced no significant change in bioelectric properties in non-cystic fibrosis tissues, but induced a 26.2% (6.3%) increase in potential difference in cystic fibrosis airways. The latter response was reduced by amiloride pretreatment. Mucosal chloride substituted Krebs-Henseleit solution caused no change in bioelectric properties in cystic fibrosis airways. Sodium substituted Krebs solution produced a substantial fall in potential difference similar in magnitude to that seen after amiloride. Isotropic flux measurements showed no significant differences between non-cystic fibrosis and cystic fibrosis airways. No net movement of Na+ or Cl- was detected under open circuit conditions in either group. CONCLUSIONS: Cystic fibrosis bronchi obtained at heart-lung transplantation provide a viable source of tissue for in vitro studies of bioelectric properties. The increased response to amiloride characteristic of the upper airways in cystic fibrosis is retained in these tissues, as is the reduced chloride conductance. Although no differences in isotopic fluxes were seen between non-cystic fibrosis and cystic fibrosis tissues, heavily infected airways from patients with cystic fibrosis may not be suitable for ion flux measurements.

Amiloride↗
PubMed1992

Wegener's granuloma. A series of 265 British cases seen between 1975 and 1985. A report by a sub-committee of the British Thoracic Society Research Committee.

In order to describe the British experience of Wegener's granulomatosis Hospital Activity Analysis was used to collect cases diagnosed in England, Wales and Scotland between 1975 and 1985. Where possible clinical details, histological material and chest radiographs were obtained. Two hundred and sixty five patients were considered to have Wegener's granulomatosis. In 109 a single pathologist confirmed the diagnosis by finding both granulomas and vasculitis in biopsy material. The diagnosis was made on clinical grounds or clinical grounds together with histological diagnosis in the local hospital in 156 patients. Wegener's granulomatosis was confined to the lung or upper respiratory tract in 22 per cent of patients and renal disease occurred in 58 per cent. Laboratory tests showed a pattern of mild anaemia, polymorph leucocytosis, eosinophilia and an elevated ESR and hypergammaglobulinaemia, with no specific pattern of changes. Histological confirmation was most frequently obtained by examination of nasal biopsy specimens, but multiple biopsies were often required. Renal biopsies showed focal proliferative glomerulonephritis but granulomatous glomerulonephritis was uncommon. Of available chest radiographs 61 per cent were abnormal, large opacities being most common. Small irregular opacities were found less often and other abnormalities were uncommon. Treatment varied widely and 10 per cent of patients received no drug therapy. This large series illustrates that even without specific treatment, patients with Wegener's granulomatosis can survive for several years and with modern treatment survival for more than a decade is possible. Conclusions about the effectiveness of the various therapies cannot be drawn from this retrospective study. Renal failure and disseminated vasculitis were the commonest causes of death; death was considered to result from complications of treatment with cytotoxic drugs or prednisolone in 6 per cent of patients.

Adolescent↗
PubMed1991

Quality of life in lung cancer.

The prognosis of a patient with lung cancer is poor and the quality is at least as important as the quantity of remaining life. Quality of life is a useful concept which is almost impossible to define but there are a number of important factors which contribute to it. Culture, religion, previous experience and the point of view of the individual all contribute to which of these factors are considered most important. Any quality of life assessment will, therefore, only apply to a defined community. The measurement of quality of life in cancer trials should concentrate on a few important categories such as physical symptoms, psychology and social factors and should be simple rather than comprehensive. In addition, a few frequent measures are better than an occasional comprehensive survey and ideally, both approaches should be combined and compared. Such measurements are most useful for comparative trials rather than for making an overall quality of life estimate. Finally, for routine clinical use outside clinical trials the quality of life index or the Karnofsky scale is recommended.

Aged↗
PubMed1991

A randomised trial of planned versus as required chemotherapy in small cell lung cancer: a Cancer Research Campaign trial.

In a study of chemotherapy as palliative treatment, 300 patients with untreated limited and extensive stage small cell lung cancer (SCLC), who did not have progressive disease after the first cycle of chemotherapy, were randomised to receive either regular 'planned' chemotherapy or chemotherapy given 'as required' (AR). All patients received the same chemotherapy: cyclophosphamide 1 gm m-2 i.v., vincristine 2 mg i.v., and etoposide 120 mg m-2 i.v. on day 1, and etoposide 100 mg b.d. orally on days 2 and 3. Planned chemotherapy was given regularly every 3 weeks. AR chemotherapy was given for tumour-related symptoms, or for radiological progression of disease. Both groups of patients were assessed every 3 weeks and a maximum of eight cycles of chemotherapy was given. A detailed quality of life assessment was made using daily diary cards. The median survival (MS) of patients given AR chemotherapy was not significantly worse than those receiving planned treatment [MS: Planned = 36 weeks (95% C.I. 32-40 weeks), AR = 32 weeks (95% C.I. 28-37 weeks) P = 0.960]. In the AR patients the median interval between treatments was 42 days. On average AR patients received half as much chemotherapy as planned patients. AR patients with a treatment-free interval (TFI) of more than 8 weeks between the first and second cycles of chemotherapy survived longer than those in whom this interval was less than 4 weeks; [MS: TFI greater than 8 = 47 weeks (95% C.I. 32-53 weeks); TFI less than 4 = 24 weeks (95% C.I. 17-34 weeks) P = 0.013]. Contrary to expectation, in the quality of life assessment the AR patients scored themselves as having more severe symptoms than patients receiving planned treatment. AR chemotherapy is a novel method of attempting to use cytotoxic drugs palliatively, which resulted in less drug treatment for approximately equivalent survival. However the palliative effect seen with as required treatment was less satisfactory than with planned chemotherapy.

Aged↗