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Biomedical subjects

A Markham

Publications and source records attributed to A Markham.

At least 73 records · Page 4Linked to original sources
PubMed1996

Epoetin beta. A review of its pharmacological properties and clinical use in the management of anaemia associated with chronic renal failure.

Epoetin beta is a recombinant form of erythropoietin, the hormone responsible for the maintenance of erythropoiesis. The drug binds to and activates receptors on erythroid progenitor cells which then develop into mature erythrocytes. Epoetin beta increases reticulocyte counts, haemoglobin levels and haematocrit in a dose-proportional manner. These changes are accompanied by beneficial cardiovascular effects, including decreased cardiac output, resting heart rate and left ventricular hypertrophy in patients with chronic renal failure (CRF). Increases of 15 to 54% in haemoglobin levels and 17 to 60% in haematocrit were reported after subcutaneous or intravenous epoetin beta therapy in studies of 8 weeks' to 12 months' duration. Two multicentre clinical trials demonstrated clearly the superior efficacy of epoetin beta over placebo in 229 patients with CRF undergoing haemodialysis. Reduction or elimination of transfusion requirements was reported in studies where this parameter was measured. Comparative data indicate that dosage reductions of approximately 30% compared with intravenous therapy are possible when subcutaneous administration of epoetin beta is used. Haematocrit increased more rapidly in 5 multicentre studies in patients who received epoetin beta subcutaneously than in those who received the same dosage intravenously. Correction of anaemia with epoetin beta is associated with significant improvements in quality of life in patients with CRF. Available data indicate greatest cost-effectiveness in patients who are severely incapacitated by anaemia before treatment. The cost of administration of the drug may also be reduced by the use of the subcutaneous route. Hypertension may occur in patients who receive epoetin beta but may be minimised by avoiding rapid increases in haematocrit (> 0.5%/week), and is managed in most cases with control of fluid status and antihypertensive medication. Although clotting of the vascular access has not been conclusively linked to epoetin beta, caution is recommended in patients undergoing haemodialysis. Increased heparinisation is recommended to prevent clotting in dialysis equipment. Epoetin beta is more effective and/or better tolerated than alternative treatments (e.g. androgenic steroids) for anaemia associated with CRF. It also causes significant improvements in quality of life, exercise capacity and overall well-being. Results of clinical studies indicate that subcutaneous administration is desirable where possible in the majority of patients. Thus, epoetin beta has become established as an effective treatment for anaemia associated with CRF.

Anemia↗
PubMed1996

Ciprofloxacin. An updated review of its pharmacology, therapeutic efficacy and tolerability.

Ciprofloxacin is a broad spectrum fluoroquinolone antibacterial agent. Since its introduction in the 1980s, most Gram-negative bacteria have remained highly susceptible to this agent in vitro; Gram-positive bacteria are generally susceptible or moderately susceptible. Ciprofloxacin attains therapeutic concentrations in most tissues and body fluids. The results of clinical trials with ciprofloxacin have confirmed its clinical efficacy and low potential for adverse effects. Ciprofloxacin is effective in the treatment of a wide variety of infections, particularly those caused by Gram-negative pathogens. These include complicated urinary tract infections, sexually transmitted diseases (gonorrhoea and chancroid), skin and bone infections, gastrointestinal infections caused by multiresistant organisms, lower respiratory tract infections (including those in patients with cystic fibrosis), febrile neutropenia (combined with an agent which possesses good activity against Gram-positive bacteria), intra-abdominal infections (combined with an antianaerobic agent) and malignant external otitis. Ciprofloxacin should not be considered a first-line empirical therapy for respiratory tract infections if penicillin-susceptible Streptococcus pneumoniae is the primary pathogen; however, it is an appropriate treatment option in patients with mixed infections (where S. pneumoniae may or may not be present) or in patients with predisposing factors for Gram-negative infections. Clinically important drug interactions involving ciprofloxacin are well documented and avoidable with conscientious prescribing. Recommended dosage adjustments in patients with impaired renal function vary between countries; major adjustments are not required until the estimated creatinine clearance is < 30 ml/min/1.73m2 (or when the serum creatinine level is > or = 2 mg/dl). Ciprofloxacin is one of the few broad spectrum antibacterials available in both intravenous and oral formulations. In this respect, it offers the potential for cost savings with sequential intravenous and oral therapy in appropriately selected patients and may allow early discharge from hospital in some instances. In conclusion, ciprofloxacin has retained its excellent activity against most Gram-negative bacteria, and fulfilled its potential as an important antibacterial drug in the treatment of a wide range of infections. Rational prescribing will help to ensure the continued clinical usefulness of this valuable antimicrobial drug.

Anti-Infective Agents↗
PubMed1996

Ropivacaine. A review of its pharmacology and therapeutic use in regional anaesthesia.

The enantiomerically pure (S-enantiomer) amide local anaesthetic drug ropivacaine blocked nerve fibres responsible for transmission of pain (A delta and C fibres) more completely than those that control motor function (A beta fibres) in in vitro studies. The drug shares the biphasic vascular effects common to the amide local anaesthetic drug class. In vitro studies indicate that ropivacaine is less cardiotoxic than equimolar concentrations of bupivacaine. Apart from one trial in women undergoing hysterectomy, clinical studies that compared the efficacy of different doses of epidurally administered ropivacaine in patients undergoing various surgical procedures did not reveal any consistent dose-related differences with respect to sensory blockade. However, motor blockade did become more intense as the dose of ropivacaine increased. Overall, direct comparisons show that epidural ropivacaine is less potent than epidural bupivacaine when the 2 drugs are administered at the same concentration. However, this difference is less marked in terms of sensory blockade than motor blockade. The greater degree of separation between motor and sensory blockade seen with ropivacaine relative to bupivacaine is more apparent at the lower end of the dosage scale. Nevertheless, higher doses of ropivacaine than bupivacaine are generally required to elicit equivalent anaesthetic effects. Ropivacaine has been shown to induce successful brachial plexus anaesthesia when given at a concentration of 5 mg/ml, but not 2.5 mg/ml, and was as effective as bupivacaine in comparative studies in this indication. Limited data indicate that continuous epidural infusion of ropivacaine postoperatively reduces postsurgical pain in a dose-related manner. Morphine consumption was also reduced. Higher doses of ropivacaine were significantly more effective than placebo. Similarly, ropivacaine controlled postsurgical pain when infiltrated directly into surgical wound sites (i.e. would infiltration) and was as effective as bupivacaine, and more effective than placebo, in this regard. Adverse events associated with epidurally administered ropivacaine include hypotension, nausea, bradycardia, transient paraesthesia, back pain, urinary retention and fever. The drug appears to have an adverse event profile similar to that of bupivacaine. In animal studies, overdoses of ropivacaine were better tolerated than overdoses of bupivacaine but not lidocaine (lignocaine). Human volunteers tolerated a higher intravenous dosage of ropivacaine than bupivacaine before developing initial signs of toxicity. Thus, ropivacaine, according to animal data, is less cardiotoxic than bupivacaine. Based on available clinical data, ropivacaine appears to be as effective and well tolerated as bupivacaine when equianalgesic doses are compared. The greater degree of separation between motor and sensory blockade seen withropivacaine relative to bupivacaine at lower concentrations (approximately 5 mg/ml) will be advantageous in certain applications.

Amides↗
PubMed1996

Irinotecan. A review of its pharmacological properties and clinical efficacy in the management of advanced colorectal cancer.

Irinotecan (CPT-II) is a semisynthetic derivative of camptothecin. It and other camptothecin analogues/derivatives appear to exert their antitumour activity by binding to topoisomerase I. The active metabolite of irinotecan, 7-ethyl-10-hydroxycamptothecin (SN-38), has demonstrated potent growth inhibition of human colorectal cancer cells in vitro, with superior activity to fluorouracil. In phase II clinical studies in patients with advanced colorectal cancer, objective response rates after irinotecan therapy ranged between 20.5 and 32%. These studies used a range of irinotecan regimens including 350 mg/m2 once every 3 weeks (Europe), 125 to 150 mg/m2 once a week for 4 weeks followed by a 2-week drug-free interval (US) and 100 mg/m2/week or 150 mg/m2 every 2 weeks (Japan). The median duration of response ranged between 5.6 and 10.6 months. Disease stabilisation occurred in 30 to 71.2% of patients. Objective response rates to irinotecan therapy in patients who had received no prior chemotherapy were similar to those in patients pretreated with fluorouracil. Importantly, irinotecan also induced responses in some patients with tumours refractory to fluorouracil. Severe (grade 3 or 4) neutropenia and diarrhoea, which occurred in up to 40% of patients receiving irinotecan therapy in phase II studies, require careful monitoring and appropriate management. Thus, irinotecan is a valuable agent for the second-line treatment of patients with advanced colorectal cancer who fail to respond to or relapse after fluorouracil therapy.

Antineoplastic Agents, Phytogenic↗
PubMed1996

Ondansetron. A review of its pharmacology and preliminary clinical findings in novel applications.

The use of ondansetron, a selective serotonin 5-HT3 receptor antagonist, is well established in patients with nausea and vomiting associated with cancer chemotherapy, radiotherapy or anaesthesia and surgery. The wide distribution of 5-HT3 receptors in the body and the role of these receptors in disease have provided the rationale for investigation of ondansetron in novel applications. Preliminary data have shown ondansetron to have clinical benefit in patients with nausea and vomiting associated with drug overdosage or poisoning, anti-infective or antidepressant therapies, uraemia or neurological trauma, and in patients with pruritus. Patients with gastrointestinal motility disorders (e.g. carcinoid syndrome, irritable bowel syndrome, diarrhoea associated with cryptosporidiosis or diabetes, and chronic refractory diarrhoea) have also shown some improvement when treated with ondansetron, as have patients with certain pain or CNS-related disorders [e.g. alcohol (ethanol) dependence, opiate withdrawal, vertigo, cerebellar tremor and Parkinson's disease treatment-related psychosis]. In contrast to conventional antiemetics, ondansetron is generally well tolerated with a lower incidence of sedation and only isolated case reports of extrapyramidal reactions. Furthermore, unlike dopamine receptor-blocking neuroleptics, ondansetron does not appear to worsen the symptoms of Parkinson's disease. Thus, in addition to its established indications, preliminary results suggest that ondansetron may be beneficial in a number of novel applications. This drug may represent a treatment alternative in patients with refractory disease, or an effective treatment of conditions for which current therapies are either poorly tolerated or not available. Further investigation of ondansetron in a range of potential new applications appears to be warranted.

Animals↗
PubMed1995

Uptake of 75-Selenium into the central nervous system of the rat.

These experiments have investigated selenium movement between blood and the CNS in anaesthetized rats. Each animal was anaesthetized and the left femoral blood vessels cannulated for blood withdrawal and solute infusion. Each rat received 75-Se as sodium selenite infused in normal saline and experiments lasted between 5 minutes and 5 hours during which blood samples were periodically taken. At termination, the CNS was removed, dissected and analysed with the plasma samples for 75-Se radioactivity by gamma-counting. Data were analyzed by multiple-time uptake analysis. Results showed unidirectional uptake of 75-Se into the CNS and some regional differences were found. On average the CNS influx rate constant (Kin) was about 7 +/- 1 x 10(-5) ml/min/g. This indicates that the 75-Se most likely entered the CNS in a protein-bound form.

Animals↗
PubMed1995

Epoetin alfa. A review of its pharmacodynamic and pharmacokinetic properties and therapeutic use in nonrenal applications.

Epoetin alfa is a recombinant form of the principal hormone responsible for erythrogenesis, erythropoietin. Already an established treatment for anaemia associated with renal failure, epoetin alfa may also be used to correct anaemia in other patient groups. The drug increases the capacity for autologous blood donation in patients scheduled to undergo surgery and attenuates the decrease in haematocrit often seen in untreated autologous donors. However, transfusion requirements did not significantly decrease in many trials. Epoetin alfa also accelerates red blood cell recovery after allogeneic--but not autologous--bone marrow transplant. Limited data in patients with adult rheumatoid arthritis suggest that while epoetin alfa increases haematocrit/haemoglobin levels, overall clinical rheumatological status may not improve. However, the drug did improve quality of life in a small cohort of children with juvenile rheumatoid arthritis in addition to correcting anaemia. Response rates to treatment with epoetin alfa in patients with anaemia associated with cancer range between 32 and 85%. Anaemia associated with cancer chemotherapy also responds well to treatment with the drug as does anaemia associated with zidovudine therapy in patients with acquired immune deficiency syndrome (AIDS). Studies evaluating the use of epoetin alfa as treatment for anaemia of prematurity have used different methodologies and dosages, making overall analysis difficult. Nevertheless, it appears that high dosages are necessary for response. Results from 1 study suggest that treatment with epoetin alfa appears to be more costly than transfusional support in this application; the relevance of this finding is questionable, however, given that the aim of treatment with epoetin alfa is elimination of transfusion requirements. The incidence of many adverse events associated with epoetin alfa treatment in patients with renal failure (hypertension, seizures and thromboembolic events) has been minimal in patients without renal failure. Adverse events occurred at a similar rate in placebo and epoetin alfa recipients in placebo-controlled trials evaluating the use of the drug as treatment for anaemia in patients with cancer receiving chemotherapy or patients with AIDS receiving zidovudine. In summary, epoetin alfa is an effective alternative to blood transfusion, reducing anaemia and producing consequent improvements in quality of life in many nonrenal applications. It was more effective than placebo in a number of double-blind trials and may be particularly useful as treatment for anaemia associated with other drugs such as cisplatin and zidovudine.

Absorption↗
PubMed1995

Cefixime. A review of its therapeutic efficacy in lower respiratory tract infections.

Cefixime is an orally active third generation cephalosporin with in vitro antibacterial activity against most important lower respiratory pathogens. The drug is active against Haemophilus influenzae, Moraxella catarrhalis and penicillin-susceptible Streptococcus pneumoniae but not Staphylococcus aureus. Cefixime has a long elimination half-life (3 hours compared with 0.5 hours for cefaclor and 1.5 hours for cefalexin), which allows once daily administration. Several trials have established the clinical efficacy of the drug in patients with lower respiratory tract infection (LRTI). In comparative studies cefixime had similar efficacy to amoxicillin +/- clavulanic acid, cefaclor, cefalexin, cefuroxime axetil and clarithromycin. Trials evaluating the efficacy of cefixime as the oral component of intravenous to oral switch therapy have produced promising preliminary results although further carefully designed trials are needed in this area. As with certain other drugs of its class, gastrointestinal disturbances are the most frequently reported adverse events in patients taking cefixime and cases of pseudomembranous colitis have been reported. Thus, cefixime is an effective treatment for mild to moderate LRTI and may have a role as the oral component of intravenous to oral switch therapy although further well designed studies are needed to confirm initial favourable results in this important emerging area of antibacterial therapy.

Anti-Bacterial Agents↗
PubMed1995

Deflazacort. A review of its pharmacological properties and therapeutic efficacy.

Deflazacort is an oxazoline derivative of prednisolone with anti-inflammatory and immunosuppressive activity. Both short (4 to 6 weeks) and longer term (13 to 52 weeks) studies have shown deflazacort to be as effective as prednisone or methylprednisolone in patients with rheumatoid arthritis. The drug was at least as effective as prednisone in children with juvenile chronic arthritis. Insufficient data are available to draw firm conclusions regarding the efficacy of deflazacort as treatment for patients with severe asthma, but the drug has demonstrated some efficacy as treatment for nephrotic syndrome and other applications such as Duchenne dystrophy, systemic lupus erythematosus, uveitis and transplantation. The overall incidence of adverse events in deflazacort recipients (16.5%) is lower than that recorded in patients treated with prednisone (20.5%) or methylprednisolone (32.7%) and similar to that in betamethasone recipients (15.3%). Gastrointestinal symptoms are the most frequently reported adverse events in deflazacort recipients; other adverse events associated with the drug include metabolic and nutritional disorders, central and peripheral nervous system disturbances and psychiatric disorders. In general, deflazacort appears to have less effect than prednisone on parameters which may be associated with the development of corticosteroid-induced osteoporosis. Further, the drug appears have less negative impact on growth rate in children with diseases requiring corticosteroid therapy. In a study of 2 months' duration in patients with conditions requiring corticosteroid treatment, moderate dosages of deflazacort produced no clinically relevant diabetogenic effects. Thus, deflazacort may be associated with less serious metabolic sequelae than prednisone but further well designed long term trials are required to confirm this. In the meantime, in adults, deflazacort should be reserved for use in those pre-disposed to, or who develop, intolerable metabolic sequelae during treatment with corticosteroids. In children, however, even though available efficacy data are minimal, deflazacort should be considered as an initial option in those requiring corticosteroid therapy since the adverse effects caused by this drug class are particularly debilitating in this patient group.

Anti-Inflammatory Agents↗
PubMed1995

Cyclosporin. A review of the pharmacokinetic properties, clinical efficacy and tolerability of a microemulsion-based formulation (Neoral).

The microemulsion-based formulation of cyclosporin (Neoral; referred to as the microemulsion formulation in this review) is a microemulsion preconcentrate which has been developed to overcome problems associated with the poor and unpredictable absorption of the standard oral formulation of this drug. These include marked intra- and interpatient variability in the extent of absorption, a poor correlation between trough blood concentrations of cyclosporin and total systemic exposure, and the need for regular monitoring of blood cyclosporin concentrations. In healthy volunteers and renal or liver transplant recipients, administration of the microemulsion formulation resulted in cyclosporin absorption which was significantly faster, more extensive and more predictable than that seen with the standard oral formulation. Furthermore, measurement of whole-blood trough cyclosporin concentrations provided a better estimate of systemic drug exposure in renal transplant recipients who received the microemulsion formulation than in those who received the standard formulation. Systemic exposure of cyclosporin delivered by the new formulation appears to be relatively unaffected by food intake. Initial data suggest that drug absorption from the microemulsion formulation is enhanced in comparison with that achieved from the standard formulation in liver transplant recipients undergoing biliary diversion or with cholestasis, although absorption from the new formulation does not appear to be completely independent of bile. Preliminary results from other groups that experience cyclosporin malabsorption from the standard formulation (patients with cystic fibrosis or diabetes, and children) are also encouraging. Clinical trials specifically designed to investigate the relative immunosuppressive efficacy of the microemulsion formulation have not been reported; further data are required to fully establish the relationship between the more rapid and extensive absorption of cyclosporin from the microemulsion formulation and the probability of graft rejection or adverse events (including nephrotoxicity and hypertension). However, no statistically significant differences have been noted between the 2 formulations in the incidence of these events in studies to date. The incidence of rejection in new renal or liver transplant recipients treated for a minimum of 3 months was approximately 31 to 50% in those receiving the microemulsion formulation and approximately 24 to 56% in those receiving the standard formulation. Thus, although confirmation of existing efficacy and tolerability data is required, the characteristic pharmacokinetic properties of the microemulsion formulation make it an attractive option for the oral delivery of cyclosporin in transplant recipients, offering more predictable and more extensive drug absorption than the standard formulation. The microemulsion formulation may be of particular benefit in patients who show poor absorption of cyclosporin from the standard oral formulation, such as liver transplant recipients with biliary diversion or cholestasis.

Animals↗
PubMed1994

Roxithromycin. An update of its antimicrobial activity, pharmacokinetic properties and therapeutic use.

Roxithromycin is a derivative of the macrolide antibacterial erythromycin with in vitro antibacterial activity resembling that of the parent compound. The drug has activity against some Staphylococcus spp., many Streptococcus spp., Moraxella (Branhamella) catarrhalis, Mycoplasma pneumoniae, Legionella pneumophila and Chlamydia trachomatis as well as many less common organisms. Measured using recently proposed guidelines, roxithromycin has in vitro activity against Haemophilus influenzae. In comparison with that of its parent compound, the pharmacokinetic profile of roxithromycin is characterised by high plasma, tissue and body fluid concentrations and a long half-life permitting an extended dosage interval. Roxithromycin has proven clinical efficacy in upper and lower respiratory infections, skin and soft tissue infections, urogenital infections and orodental infections, and appears to be as effective as more established treatments including erythromycin, amoxicillin/clavulanic acid and cefaclor. The drug has also shown promise in a variety of more specialised indications including opportunistic infections in human immunodeficiency virus (HIV)-positive patients and as part of a Helicobacter pylori eradication regimen. Roxithromycin is very well tolerated with an overall incidence of adverse events of approximately 4%. Thus, roxithromycin is an attractive therapeutic alternative in its established indications, especially when the option of once-daily administration is considered.

Absorption↗
PubMed1994

Nimesulide. An update of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy.

Nimesulide is a nonsteroidal anti-inflammatory drug (NSAID) administered orally or rectally twice daily for a variety of inflammatory and pain states. In mostly short term studies (up to 4 weeks), it was effective in reducing pain associated with osteoarthritis, cancer, thrombophlebitis, oral surgery and dysmenorrhoea in adults, reducing pain associated with general surgery in adults and children, and pain, fever and inflammation accompanying respiratory tract infections, otorhinolaryngological diseases and traumatic injury in adults and children. Nimesulide appeared to be at least as effective as other NSAIDs in all of these indications. Nimesulide has been well tolerated by adult, elderly and paediatric patients in clinical trials and large postmarketing surveillance studies. In general qualitative terms nimesulide exhibits the usual adverse events associated with NSAIDs (gastrointestinal, dermatological and neurological). However, it has a pharmacodynamic profile suggestive of a possibly reduced propensity to cause adverse gastrointestinal effects, although this has not been conclusively demonstrated in comparative clinical trials, many of which showed a similar incidence of such effects for nimesulide and the comparator agent. Additionally, nimesulide has been well tolerated by most aspirin (acetylsalicylic acid)- and/or NSAID-intolerant patients and in patients with asthma. Thus, available evidence indicates that nimesulide is an effective and well tolerated alternative to other NSAIDs in the short term treatment of pain and inflammation of osteoarthritis and various other causes.

Animals↗
PubMed1993

Calcium antagonists and Bay K8644 promote depolarization of the rat heart mitochondrial membrane potential. Further evidence for a role in alteration of oxidative metabolism.

Studies were carried out using a tetraphenylphosphonium (TPP+)-selective electrode to monitor the effect of selected calcium (Ca2+) antagonists and the dihydropyridine Ca2+ agonist Bay K8644 on membrane potential (psi) associated with isolated rat heart mitochondria. Verapamil and diltiazem (10-500 microM), standard Ca2+ antagonists, produced a depolarization of both liver and heart mitochondria at concentrations > 150 microM. In contrast, nitrendipine (10-200 microM), a dihydropyridine compound, produced a concentration-related inhibition of psi in mitochondria from both sources, effects which were statistically significant at concentrations > 50 microM. Cinnarizine (10-100 microM) and bepridil (10-100 microM) also produced inhibition of heart psi, these effects being particularly noted in the presence of bepridil, where depolarization of the membrane was statistically significant with only 10 microM drug. The results indicate the complexity of action of these drugs at the mitochondrial level. In general, drug actions on psi appear to be correlated with previously reported effects on Ca2+ transportation rather than oxidative phosphorylation associated with rat heart mitochondria. The findings also illustrate that the mitochondrial actions of cardiovascular compounds may be of relevance in situ, particularly during ischaemia/reperfusion when mitochondria become loaded with Ca2+.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1991

Identification of a gene located at chromosome 5q21 that is mutated in colorectal cancers.

Recent studies have suggested the existence of a tumor suppressor gene located at chromosome region 5q21. DNA probes from this region were used to study a panel of sporadic colorectal carcinomas. One of these probes, cosmid 5.71, detected a somatically rearranged restriction fragment in the DNA from a single tumor. Further analysis of the 5.71 cosmid revealed two regions that were highly conserved in rodent DNA. These sequences were used to identify a gene, MCC (mutated in colorectal cancer), which encodes an 829-amino acid protein with a short region of similarity to the G protein-coupled m3 muscarinic acetylcholine receptor. The rearrangement in the tumor disrupted the coding region of the MCC gene. Moreover, two colorectal tumors were found with somatically acquired point mutations in MCC that resulted in amino acid substitutions. MCC is thus a candidate for the putative colorectal tumor suppressor gene located at 5q21. Further studies will be required to determine whether the gene is mutated in other sporadic tumors or in the germ line of patients with an inherited predisposition to colonic tumorigenesis.

Adenomatous Polyposis Coli↗
PubMed1991

A deletion mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) locus: Delta I507.

During the development of an amplification refractory mutation system (ARMS) assay for the detection of the Delta F508 mutation and corresponding normal locus in cystic fibrosis we discovered a family in which a further variant of the sequence exists. PCR amplification and direct sequencing of a region of exon 10 of the CFTR locus indicated the deletion of the three base pairs encoding isoleucine or isoleucine, or possibly the presence of a single base substitution in conjunction with the Delta F508 mutation. The resulting protein has a deletion of an isoleucine residue at position 507 as opposed to the previously described deletion of phenylalanine at position 508. We conclude that the loss of an isoleucine residue at position 507 (Delta I507) is another defective variant of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene product.

Amino Acid Sequence↗
PubMed1991

Ca2+ ion sequestration by guinea-pig tracheal cartilage: its influence on trachealis reactivity to KCl.

1. The contractile response of guinea-pig isolated trachealis to KCl has been studied in the presence and absence of cartilage. 2. Dissection of cartilage from the trachealis resulted in both a rightward displacement of the concentration-response curve to KCl (EC50 value: intact strip, 26.9 +/- 3.7 mM n = 5; dissected strip, 38.7 +/- 2.6 mM n = 5; P less than 0.05), and a reduction in the contractile response to KCl (30 mM) observed in a nominally Ca(2+)-free medium. 3. Removal of cartilage from the trachealis did not alter the responsiveness of the tissue to CaCl2 (2.5 mM) when added to K+ depolarized tissues. 4. Muscle-denuded cartilage rings were prepared by surgical removal of the trachealis muscle. Autoradiographic studies, and a direct comparison of Ca2+ (2.5 mM) uptake with that of sorbitol (2.5 mM) showed that cartilage per se had a high capacity to accumulate Ca2+ ions by a process which was resistant to iodoacetate (100 microM), diflunisal (100 microM) and boiling. 5. The uptake of 45Ca into isolated cartilage was unaltered by the addition of orthovanadate (500 microM), verapamil (10 microM), diltiazem (10 microM) or Bay K 8644 (10 microM), but was significantly reduced (P less than 0.05) in the presence of LaCl3 (1-10 mM). 6. We conclude, like previous studies, that cartilage may supply a pool of Ca2+ ions to airway smooth muscle during the generation of tension in a noninally Ca(2+)-free medium, and that LaCl3 may provide an experimental tool to elucidate further the role of non-muscle Ca(2+)-depots in smooth muscle contraction.

Animals↗
PubMed1990

Delta F508 testing of the DNA bank of the Royal Manchester Children's Hospital.

Details of haplotype and delta F508 status from various populations represented in the cystic fibrosis (CF) DNA bank of the Royal Manchester Children's Hospital are provided, together with information on the association of genotype and clinical status. Clinical details and DNA analyses from native English in the North-West and South-West of England (Bath), from Lancashire Pakistani families and from Afrikaans Namibian families are compared. A 78.5% incidence of delta F508 has been found in English families. Compound heterozygotes with CF and only one delta F508 gene have an increased likelihood of having milder disease, with less Pseudomonas isolated from sputum and relatively more showing either no regular respiratory pathogens or colonisation with Staphylococcus. There is also a relative increase in meconium ileus in these compound heterozygotes. The diagnosis of CF may be in doubt in some subjects negative for delta F508. Some of the Bath families have unusual haplotypes for an English population and a compound heterozygote delta F508/delta I507 has been found. There is evidence from metD analysis of the founder effect in the Afrikaans Namibian families, who have a high delta F508 incidence.

Cystic Fibrosis↗