Biomedical subjects

A Woolfson

Publications and source records attributed to A Woolfson.

7 recordsLinked to original sources

PubMed2006

Facilitated delivery of ALA to inaccessible regions via bioadhesive patch systems.

5-Aminolevulinic acid (ALA) is now being increasingly used in photodynamic therapy (PDT) and photodiagnosis (PDD) of lesions of the oral cavity, esophagus, and female genital tract. Clearly, topically applied creams and solutions are not the most suitable drug delivery systems for such moist and irregularly shaped areas, where shear forces may be high. As a result, such areas of the body are currently relatively inaccessible to efficient topical delivery of ALA. The use of a bioadhesive patch for topical delivery of ALA to the lower female genital tract and now, for the first time, to the human lip, is described. Use of the patch, containing 38 mg ALA cm-2, allowed successful PDT of vulval intraepithelial neoplasia lesions and induced protoporphyrin IX production in Herpes simplex lesions of the lip.

Administration, Topical↗

PubMed2001

Ligand-independent assembly of recombinant human CD1 by using oxidative refolding chromatography.

CD1 is an MHC class I-like antigen-presenting molecule consisting of a heavy chain and beta(2)-microglobulin light chain. The in vitro refolding of synthetic MHC class I molecules has always required the presence of ligand. We report here the use of a folding method using an immobilized chaperone fragment, a protein disulphide isomerase, and a peptidyl-prolyl cis-trans isomerase (oxidative refolding chromatography) for the fast and efficient assembly of ligand-free and ligand-associated CD1a and CD1b, starting with material synthesized in Escherichia coli. The results suggest that "empty" MHC class I-like molecules can assemble and remain stable at physiological temperatures in the absence of ligand. The use of oxidative refolding chromatography thus is extended to encompass complex multisubunit proteins and specifically to members of the extensive, functionally diverse and important immunoglobulin supergene family of proteins, including those for which a ligand has yet to be identified.

Antigens, CD1↗

PubMed2001

Human CD1d-glycolipid tetramers generated by in vitro oxidative refolding chromatography.

CD1 molecules are specialized in presenting lipids to T lymphocytes, but identification and isolation of CD1-restricted lipid specific T cells has been hampered by the lack of reliable and sensitive techniques. We here report the construction of CD1d-glycolipid tetramers from fully denatured human CD1d molecules by using the technique of oxidative refolding chromatography. We demonstrate that chaperone- and foldase-assisted refolding of denatured CD1d molecules and beta(2)-microglobulin in the presence of synthetic lipids is a rapid method for the generation of functional and specific CD1d tetramers, which unlike previously published protocols ensures isolation of CD1d tetramers loaded with a single lipid species. The use of human CD1d-alpha-galactosylceramide tetramers for ex vivo staining of peripheral blood lymphocytes and intrahepatic T cells from patients with viral liver cirrhosis allowed for the first time simultaneous analysis of frequency and specificity of natural killer T cells in human clinical samples. Application of this protocol to other members of the CD1 family will provide powerful tools to investigate lipid-specific T cell immune responses in health and in disease.

Animals↗

PubMed2000

Bacterial and yeast chaperones reduce both aggregate formation and cell death in mammalian cell models of Huntington's disease.

Huntington's disease (HD) is an autosomal dominant neurodegenerative condition caused by expansions of more than 35 uninterrupted CAG repeats in exon 1 of the huntingtin gene. The CAG repeats in HD and the other seven known diseases caused by CAG codon expansions are translated into long polyglutamine tracts that confer a deleterious gain of function on the mutant proteins. Intraneuronal inclusions comprising aggregates of the relevant mutant proteins are found in the brains of patients with HD and related diseases. It is crucial to determine whether the formation of inclusions is directly pathogenic, because a number of studies have suggested that aggregates may be epiphenomena or even protective. Here, we show that fragments of the bacterial chaperone GroEL and the full-length yeast heat shock protein Hsp104 reduce both aggregate formation and cell death in mammalian cell models of HD, consistent with a causal link between aggregation and pathology.

Amino Acid Substitution↗

PubMed1997

Nasopharyngeal carriage of community-acquired, antibiotic-resistant Streptococcus pneumoniae in a Zambian paediatric population.

The emergence of antibiotic-resistant Streptococcus pneumoniae is an international health problem. Apart from South Africa few data on pneumococcal resistance are available for sub-Saharan Africa. This study examines the nasopharyngeal carriage and prevalence of antibiotic resistance in pneumococci isolated from 260 Zambian children aged < 6 years. Pneumococci were isolated from 71.9% of the children; the odds of carrying organisms were twice as high among children < 2 years of age compared with older children. Antibacterial resistance was found in 34.1% of the isolates; resistance to tetracycline, penicillin, sulfamethoxazole + trimethoprim, and chloramphenicol occurred in 23.0%, 14.3%, 12.7%, and 3.9% of the isolates, respectively. Only 4% of the isolates were resistant to three drugs. High-level resistance was found in all isolates resistant to tetracycline; but only intermediate level penicillin resistance was found. A total of 11.1% of the isolates demonstrated intermediate resistance to sulfamethoxazole + trimethoprim. Children aged < 6 months were less likely to carry antibiotic-resistant organisms. Antibiotic resistance in S. pneumoniae appears to be an emerging public health problem in Zambia, and the national policy for the empirical treatment of pneumococcal meningitis and acute respiratory tract infections may need to be re-evaluated. The establishment of ongoing surveillance to monitor trends in pneumococcal resistance should be considered.

Age Factors↗

PubMed1994

Alternative splicing generates secretory isoforms of human CD1.

Human CD1 genes are a family of five non-polymorphic genes that, although homologous to both class I and II major histocompatibility complex genes, map to chromosome 1. Only three of the antigens, CD1a, -b, and -c, have been clustered with monoclonal antibodies. They are noncovalently associated with beta 2-microglobulin and may function as nonclassical antigen-presenting molecules. Here we analyze their expression in mouse myeloma transfectants and human thymocytes and find mRNA splicing complexity. This manifests itself as incomplete splicing, alternative splicing, utilization of cryptic splice sites, and the generation of alternative reading frames. In the case of CD1A transfectants, we demonstrate that the major protein product is secreted and show by amino acid sequence analysis that this is derived from an unspliced transcript. A second major CD1a component appears to be retained intracellularly. The production of alternatively spliced transcripts in the thymus is not a feature of all CD1 genes. Although in the case of CD1A only the transcript encoding the cell surface CD1a isoform is found, CD1C and -E produce complex intrathymic splicing patterns. The CD1C transcripts predict the expression of a secreted CD1c isoform in the human thymus, which we detect in CD1C transfectant culture supernatants. CD1 gene expression is thus characterized by considerable splicing complexity, and the difference between the splicing patterns found in different environments suggests that this is tissue specific.

Alternative Splicing↗

PubMed1990

Speculating about pyrazines.

Of the various types of alerting signals found in nature, odours are the least well understood. The worldwide distribution of pyrazines in plants, insects, terrestrial vertebrates, marine organisms, fungi and bacteria suggests that they are of special significance. We speculate that these molecules served as natural points of convergence in the evolution of widespread alerting signals, which are used for differing but related intraspecific purposes by various species. In aposematic, self-advertising toxic insects and their mimics, for example, pyrazines function as additional warning signals; preliminary data indicates that their odour can potentiate taste aversion learning in rats and the associative learning of immune suppression in mice. The latter suggests that in addition to their alerting properties, pyrazine odours may act as ectohormones which interact with predator physiology.

Animals↗