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Biomedical subjects

A Cooper

Publications and source records attributed to A Cooper.

At least 145 records · Page 8Linked to original sources
PubMed1997

Uptake of alpha-(L)-iduronidase produced by retrovirally transduced fibroblasts into neuronal and glial cells in vitro.

The uptake of recombinant alpha-(L)-iduronidase into glial and neuronal cells, produced by retrovirally transduced NIH3T3 fibroblasts, was studied. We demonstrate that: (1) neuronal and glial cells take up alpha-(L)-iduronidase released into the medium by retrovirally transduced fibroblasts expressing high levels of alpha-(L)-iduronidase; (2) both glial and neuronal cells express the cation independent mannose-6-phosphate receptor responsible for lysosomal enzyme uptake; and (3) uptake of the lysosomal enzyme can be blocked by excess free mannose-6-phosphate, but not glucose-6-phosphate. Thus, various brain cells take up alpha-(L)-iduronidase, possibly through a cation independent mannose-6-phosphate receptor mediated pathway, and this uptake is higher in actively dividing or immature brain cells. Consequently, (1) neuronal metabolism ought to be capable of cross correction by enzyme provided by genetically engineered and transplanted cells provided by bone marrow transplantation (BMT); (2) that BMT could have a more beneficial effect on neurological function if performed as early as possible; and (3) given that the uptake mechanism of glial cells has a higher capacity, it might be easier to target diseases like the leukodystrophies in which lysosomal enzymes are needed in glial cells, compared to diseases where lysosomal enzymes ought to be delivered into neurons.

3T3 Cells↗
PubMed1997

Blood pressure parameters as determinants of small artery structure in human essential hypertension.

1. Adaptive changes in small arteries may be more closely correlated with pulse pressure than with systolic, diastolic or mean blood pressures in human essential hypertension. 2. An analysis was performed on the structure of small arteries, age and blood pressure measurements obtained from 56 patients with untreated essential hypertension and 56 matched normotensive volunteers to examine the association between age, blood pressure and small artery structural parameters. 3. Essential hypertension was associated with an increase in media thickness and a decrease in lumen diameter, resulting in an increase in media/lumen ratio. 4. There was a significant correlation between age and media/lumen ratio in normotensive volunteers but not in patients with essential hypertension. 5. There was no correlation between any blood pressure and structural parameter in normotensive volunteers. 6. Both diastolic and mean blood pressures in essential hypertension correlated with media/lumen ratio (P < 0.01); systolic blood pressure correlated less well (P < 0.02). However, pulse pressure did not correlate with media/lumen ratio, suggesting that it is not a significant determinant of small artery structure in untreated essential hypertension.

Adult↗
PubMed1997

Novel mutations in Sanfilippo A syndrome: implications for enzyme function.

Sanfilippo syndrome type A or mucopolysaccharidosis IIIA (MPS IIIA) is an autosomal recessive lysosomal storage disorder caused by the deficiency of sulfamidase. The resulting lysosomal storage of heparan sulfate may lead to severe neurodegeneration preceded by progressive dementia, often combined with aggressive and hyperactive behaviour. A total of 109 patients from four different geographic areas were screened for the common mutation R245H and two other previously identified mutations. SSCP analysis of exons was used to characterize the unknown alleles. We identified 16 novel sequence variants, 12 of them likely to be pathogenic. The majority of the pathogenic variants were single base pair changes leading to missense mutations. Several single base pair deletions/insertions and one nonsense mutation were also identified. Altogether, we were able to characterize 55% of the pathogenic alleles. Sequence homology between sulfamidase and N-acetylgalactosamine 4-sulfatase, the first sulfatase to have its tertiary structure defined, suggests that amino acid residues R74 and T79, which were found to be mutated, are likely to be involved in the formation of the active site of sulfamidase. R245H accounts for 31% of the Sanfilippo A alleles in Australasia, for 19.2% of the alleles in patients from the UK and has a high frequency of 57.8% in patients from The Netherlands. The identification of mutations common in certain geographic regions or ethnic groups will help in the diagnosis of MPS IIIA and allow carrier testing and improved genetic counselling.

DNA Primers↗
PubMed1997

Certified first responder: a comprehensive model for pediatric training.

The purpose of this document is to present a general approach to educating the First Responder in Emergency Pediatric Care. The First Responder is especially important in the emergency care of the sick or injured child. The majority of mortality and morbidity associated with pediatric emergencies is a result of airway and ventilatory compromise. In addition, most airway and ventilation problems can be corrected with only basic life support interventions that are within the scope of practice of the First Responder. As a result, it is of paramount importance to assure that the First Responder is adequately trained in the initial care of the pediatric patient. This document will review some of the key objectives and topics which the First Responder needs to understand in order to adequately care for children until further emergency care arrives. Templates for lesson plans and suggested activities for training the First Responder are also presented.

Certification↗
PubMed1997

The effect of long-term oestradiol implantation on bone mineral density in postmenopausal women who have undergone hysterectomy and bilateral oophorectomy.

Twelve women who had received oestradiol implantation on demand for at least 15 years following hysterectomy with bilateral oophorectomy, underwent bone densitometry of hip and spine. Bone mass of hip and spine was significantly elevated above that of both the age matched mean to a degree hitherto undocumented. This suggests that oestrogen in high doses or over a long period may produce a true anabolic effect on bone mass.

Absorptiometry, Photon↗
PubMed1997

Bone marrow transplantation for mucopolysaccharidosis type I: experience of two British centres.

Bone marrow transplantation was carried out on 38 patients with mucopolysaccharidosis type I over a period of 15 years. The donor was an HLA identical relative in 10 cases, an HLA non-identical relative in 16 cases, and an HLA identical unrelated volunteer donor in 12 cases. Ten patients received a second transplant. One patient received three transplants. Thirteen engrafted patients have survived five years or more. Most patients have shown an arrest or slowing down of psychomotor regression. However, dysostosis multiplex has progressed. Careful selection of patients may be necessary to ensure optimum results.

Bone Marrow Transplantation↗
PubMed1997

Mutation analysis in 46 British and Irish patients with Gaucher's disease.

DNA from 46 unrelated patients with Gaucher's disease was analysed for 10 known mutations: 84GG(c84 G 85ins), N370S (c1226G), L444P (c1448C), R463C (c1504T), R496H (c1604A), IVS2+1, D409H (c1342C), RecNcil (c1448C-1498C), RecTL (c1342C-1498C), and c1263del (c1264-1318del). Fifty four mutations (90%) were identified in 30 patients with type I disease. These included a previously undescribed recombinant mutation RecA456P (c1448C-1484C). Thirteen (54%) of 24 type II alleles were identified, including one new point mutation N462K (c1503G) and one new 55bp deletion also incorporating the RecTL mutations c1263del+RecTL (c1264del-1498C). All four type III patients were homozygous for the L444P point mutation. Generally, patients with one copy of the N370S mutation had mild adult onset disease, regardless of the nature of their second mutation. Three exceptions had childhood onset disease and genotypes N370S/R463C, N370S/RecA456P, and N370S/?. The L444P/L444P genotype was thought to be associated with neurological disease. Two type I patients with this genotype who exhibited no central nervous system disease were identified, however. The R463C and c1263del mutations were found to be present at a higher frequency than reported in other populations and they should be included in any mutation screen of this population. The recombinant mutations RecA456P and c1263del+RecTL have not been previously described and are the fourth and fifth recombinant mutations identified in the glucocerebrosidase gene.

Adult↗
PubMed1997

Roaccutane treatment guidelines: results of an international survey.

BACKGROUND: Oral isotretinoin (Roaccutane) revolutionized the treatment of acne when it was introduced in 1982. METHODS: Twelve dermatologists from several countries with a special interest in acne treatment met to formally review the survey of their last 100 acne patients treated with oral isotretinoin. The primary purpose of the survey was to identify the types of acne patients who were prescribed oral isotretinoin and how the patients were managed. RESULTS: Of the 1,000 patients reviewed, 55% of those who received oral isotretinoin had those indications treated historically, i.e. severe nodular cystic acne or severe inflammatory acne, not responding to conventional treatment. Forty-five percent of patients who were prescribed oral isotretinoin however had either moderate or mild acne. Most patients in this group had moderate acne (85%). However, 7.3% had mild acne on physical examination. The criteria for prescribing oral isotretinoin in this less severe group of patients included acne that improves < 50% after 6 months of conventional oral antibiotic and topical combination therapy, acne that scars, acne that induces psychological distress and acne that significantly relapses during or quickly after conventional therapy. Treatment is usually initiated at daily doses of 0.5 mg/kg (but may be higher) and is increased to 1.0 mg/kg. Most of the physicians aimed to achieve a cumulative dose of > 100-120 mg/kg. Mucocutaneous side-effects occur frequently but are manageable while severe systemic side-effects are rarely problematic (2%). The teratogenicity of oral isotretinoin demands responsible consideration by both female patients and their physicians. Significant cost savings when treating acne patients with oral isotretinoin as compared to other treatment modalities were further proven in this study. CONCLUSIONS: Our recommendation is that oral isotretinoin should be prescribed not only to patients with severe disease but also to patients with less severe acne, especially if there is scarring and significant psychological stress associated with their disease. Acne patients should, where appropriate, be prescribed isotretinoin sooner rather than later.

Acne Vulgaris↗
PubMed1997

Information delivery: the provision of written information for patients following coronary angiography and post-discharge management.

To improve management of risk factors in patients diagnosed with significant coronary artery disease after day case angiography, we gave patients a discharge information sheet emphasising the importance of prognostic therapy, risk factors and follow-up. The sheet was evaluated in 40 patients. A nurse talked through the information sheet with the patients after their angiogram and helped to complete relevant sections. One group of patients was given a copy of the sheet to take home, while the second group remained a 'verbal information only' group. Providing written information resulted in improvements in follow-up regarding blood pressure and drug therapy checks, but there was no significant difference between the groups in the follow-up management of cholesterol or in patient awareness of their cholesterol level. Patients were not likely to remember the sheet, even though a nurse had talked them through it, unless it was backed up with a written copy which could be taken away. It became apparent that the vast majority of patients remembered a pictorial representation of the extent of their disease (routinely provided) in contrast to the relatively disappointing numbers (43%) who remembered the information sheet. To evaluate further the importance of content and style in effective information delivery, we are evaluating the combination of written information with a visual representation of the heart.

Coronary Angiography↗
PubMed1996

The central domain of colicin N possesses the receptor recognition site but not the binding affinity of the whole toxin.

Colicin N is a three-domain pore-forming colicin which kills enterobacterial cells following an initial binding to its receptor, the outer membrane porin OmpF. The receptor-binding domain of colicin N alone, and attached to the translocation domain, was overexpressed and purified using a hexahistidine tag. The receptor domain attached to the pore-forming domain was obtained by enzymatic digestion. Circular dichroism spectroscopy showed that the domains have structure in keeping with the known structure of colicin N. The receptor domain was stable, retaining both secondary and tertiary structure in 2 M guanidine hydrochloride and at low pH. It bound to both OmpF and PhoE porin-producing Escherichia coli with no toxicity and protected sensitive E. coli against intact colicin N toxicity at high domain/ colicin N ratios. Its in vitro affinity for OmpF, as determined by isothermal titration microcalorimetry, was found to be approximately 50-fold weaker than that of native colicin N. The receptor domain was readily out-competed by native colicin N in in vivo fluorescence assays which, coupled with its structural stability, suggests that its interaction with OmpF is one of weak, reversible binding. Since neither of the double domain constructs shows wild-type binding affinity either, it appears that the molecular recognition is a property of the receptor domain but that affinity is influenced by the entire molecule.

Bacterial Outer Membrane Proteins↗
PubMed1996

Localization of the active site of type II dehydroquinases. Identification of a common arginine-containing motif in the two classes of dehydroquinases.

A novel method based on electrospray mass spectrometry (Krell, T., Pitt, A. R., and Coggins, J. R. (1995) FEBS Lett. 360, 93-96) has been used to localize active site residues in the type I and type II dehydroquinases. Both enzymes have essential hyper-reactive arginine residues, and the type II enzymes have an essential tyrosine residue. The essential hyper-reactive Arg-23 of the Streptomyces coelicolor type II enzyme has been replaced by lysine, glutamine, and alanine residues. The mutant enzymes were purified and shown by CD spectroscopy to be structurally similar to the wild-type enzyme. All three mutant enzymes were much less active, for example the kcat of the R23A mutant was 30,000-fold reduced. The mutants all had reduced Km values, indicating stronger substrate binding, which was confirmed by isothermal titration calorimetry experiments. A role for Arg-23 in the stabilization of a carbanion intermediate is proposed. Comparison of the amino acid sequence around the hyper-reactive arginine residues of the two classes of enzymes indicates that there is a conserved structural motif that might reflect a common substrate binding fold at the active center of these two classes of enzyme.

Amino Acid Sequence↗
PubMed1996

Regulation of cholesterol responsive genes in ovary cells: impact of cholesterol delivery systems.

The "selective" cholesterol uptake pathway represents a bulk pathway by which many steroidogenic cells internalize lipoprotein-delivered cholesteryl esters. In the current report, we question whether cholesteryl esters entering cells via this pathway are capable of governing standard cholesterol end product feedback repression mechanisms. Cultured rat ovary granulosa cells which utilize both the "selective" and "endocytic" pathways to internalize lipoprotein-derived cholesteryl esters were used as a model system. ApoE-free hHDL3 was used to deliver cholesteryl esters to the cells exclusively by the selective pathway; hLDL was used as a control ligand which when internalized by the endocytic pathway releases cholesteryl esters which subsequently regulate the expression of the B/E (LDL)-receptor, HMG CoA reductase, and acyl-CoA:cholesterol acyltransferase (ACAT). Whereas trophic hormone (Bt2cAMP) stimulation by itself increased the activity, mRNA, and protein levels of both B/E-receptor and HMG CoA reductase, pretreatment with either lipoprotein (adjusted for equal cholesterol ester content) down-regulated this expression. Linked with these lipoprotein-related changes was an increase in activity (though not gene expression) of ACAT. The level of change in mRNA levels, protein content, and activity for the examined regulatory proteins was essentially equivalent whether the lipoprotein provided to the cells was hLDL or hHDL3. Thus, similar signals appear to have been received by the cells despite differences in the uptake and processing of the ligand-derived cholesteryl esters, and these signals resulted in identical homeostatic responses by the cells.

Animals↗
PubMed1996

Long-term in vitro correction of alpha-L-iduronidase deficiency (Hurler syndrome) in human bone marrow.

Allogeneic bone marrow transplantation is the most effective treatment for Hurler syndrome but, since this therapy is not available to all patients, we have considered an alternative approach based on transfer and expression of the normal gene in autologous bone marrow. A retroviral vector carrying the full-length cDNA for alpha-L-iduronidase has been constructed and used to transduce bone marrow from patients with this disorder. Various gene-transfer protocols have been assessed including the effect of intensive schedules of exposure of bone marrow to viral supernatant and the influence of growth factors. With these protocols, we have demonstrated successful gene transfer into primitive CD34+ cells and subsequent enzyme expression in their maturing progeny. Also, by using long-term bone marrow cultures, we have demonstrated high levels of enzyme expression sustained for several months. The efficiency of gene transfer has been assessed by PCR analysis of hemopoietic colonies as 25-56%. No advantage has been demonstrated for the addition of growth factors or intensive viral exposure schedules. The enzyme is secreted into the medium and functional localization has been demonstrated by reversal of the phenotypic effects of lysosomal storage in macrophages. This work suggests that retroviral gene transfer into human bone marrow may offer the prospect for gene therapy of Hurler syndrome in young patients without a matched sibling donor.

Antigens, CD34↗