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Biomedical subjects

Peter Howard

Publications and source records attributed to Peter Howard.

7 recordsLinked to original sources
PubMed2006

Transport of alpha-helical peptides through alpha-hemolysin and aerolysin pores.

A series of negatively charged alpha-helical peptides of the general formula fluorenylmethoxycarbonyl (Fmoc)-D(x)A(y)K(z) were synthesized, where x and z were 1, 2, or 3 and y was 10, 14, 18, or 22. The translocation of the peptides through single pores, which were self-assembled into lipid membranes, was analyzed by measuring the current blockade i(block) and the duration t(block). The pores were either alpha-hemolysin, which has a wide vestibule leading into the pore, or aerolysin, which has no vestibule but has a longer pore of a similar diameter. Many thousands of events were measured for each peptide with each pore, and they could be assigned to two types: bumping events (type I) have a small i(block) and long t(block), and translocation events (type II) have a larger i(block) and shorter t(block). For type-II events, both i(block) and t(block) increase with the length of the peptides on both pores tested. The dipole moment and the net charge of each peptide has a major effect on the transport characteristics. The ratio of type-II/type-I events increases as the dipole moment increases, and uncharged peptides gave mostly type-I events. The structural differences between the two nanopores were reflected in the characteristic values of i(block), and in particular, the vestibule of alpha-hemolysin helps to orient the peptides for translocation. Overall, the results demonstrate that the nanopore technology can provide useful structural information but peptide sequencing will require further improvements in the design of the pores.

Aeromonas hydrophila↗
PubMed2005

From workshop to work practice: An exploration of context and facilitation in the development of evidence-based practice.

BACKGROUND: This article examines the process of translating evidence into practice using a facilitation model developed by the Western Australian Centre for Evidence Based Nursing and Midwifery. AIMS: Using the conceptual framework Promoting Action on Research Implementation in Health Services (PARIHS), the aims of the study were (1) to explore the relative and combined importance of context and facilitation in the successful implementation of a new evidence-based clinical practice protocol and (2) to examine the establishment of more lasting change to individuals and organizations that resulted in greater incorporation of the principles of evidence-based practice (EBP). METHODS: A pre-workshop, semi-structured telephone survey with 16 nurse managers in six rural hospitals; a summative evaluation immediately post-workshop with 54 participants; and follow-up, semi-structured interviews with 23 workshop participants. FINDINGS: The contexts in each of the participating hospitals were very different; of the six hospitals, only one had not implemented the new protocol. Five had reviewed their practices and brought them in line with the protocol developed at the workshop. The rate of adoption varied considerably from 2 weeks to months. The participants reported being better informed about EBP in general and were positive about their ability to improve their practice and search more efficiently for best practice information. Underlying motivations for protocol development should be included in the PARIHS framework. IMPLICATIONS FOR EDUCATION: Good facilitation appears to be more influential than context in overcoming the barriers to the uptake of EBP.

Diffusion of Innovation↗
PubMed2003

Dimerization of TonB is not essential for its binding to the outer membrane siderophore receptor FhuA of Escherichia coli.

FhuA belongs to a family of specific siderophore transport systems located in the outer membrane of Escherichia coli. The energy required for the transport process is provided by the proton motive force of the cytoplasmic membrane and is transmitted to FhuA by the protein TonB. Although the structure of full-length TonB is not known, the structure of the last 77 residues of a fragment composed of the 86 C-terminal amino acids was recently solved and shows an intertwined dimer (Chang, C., Mooser, A., Pluckthun, A., and Wlodawer, A. (2001) J. Biol. Chem. 276, 27535-27540). We analyzed the ability of truncated C-terminal TonB fragments of different lengths (77, 86, 96, 106, 116, and 126 amino acid residues, respectively) to bind to the receptor FhuA. Only the shortest TonB fragment, TonB-77, could not effectively interact with FhuA. We have also observed that the fragments TonB-77 and TonB-86 form homodimers in solution, whereas the longer fragments remain monomeric. TonB fragments that bind to FhuA in vitro also inhibit ferrichrome uptake via FhuA in vivo and protect cells against attack by bacteriophage Phi80.

Amino Acid Sequence↗
PubMed2003

Sperm chromosomal abnormalities are linked to sperm morphologic deformities.

OBJECTIVE: To describe the association between specific sperm morphologic abnormalities and sperm chromosomal abnormalities on multicolor interphase fluorescence in situ hybridization (FISH). DESIGN: Case report. Reproductive medicine unit in a tertiary referral center. PATIENT(S): Three infertile men with severe oligoasthenospermia and total teratozoospermia who were referred for IVF treatment. MAIN OUTCOME MEASURE(S): Incidence of spermatozoal chromosomal aneuploidy for chromosome 18 and the sex chromosomes by using FISH. RESULT(S): Morphologic assessment of sperm revealed a high incidence of double heads, multinucleated sperm heads, and multiple tails. Hormone profiles and karyotyping of peripheral lymphocytes were normal in the three men. The proportion of sperm with disomy, trisomy and tetrasomy for chromosome 18, and the sex chromosomes in each patient was 100%, 76%, and 82.5%, respectively. CONCLUSION(S): Specific morphologic abnormalities of sperm may be associated with higher incidence of chromosomal abnormalities. Resolving infertility by offering patients in vitro fertilization/intracytoplasmic sperm injection must be approached with caution because of the significant risk for embryonic aneuploidy and chromosomal abnormalities in any subsequent offspring.

Adult↗
PubMed2002

Tuberculosis in Australia: bacteriologically confirmed cases and drug resistance, 2000: report of the Australian Mycobacterium Laboratory Reference Network.

The Australian Mycobacterium Reference Laboratory Network collected and analysed laboratory data on new diagnoses of disease caused by Mycobacterium tuberculosis complex in the year 2000. A total of 765 cases were identified, representing an annual reporting rate of 4.0 cases of laboratory-confirmed tuberculosis (TB) per 100,000 population. Pulmonary disease was diagnosed in 64.9 per cent of cases with a male:female ratio of 1.5:1. Smears were positive for 209/365 (57.3%) of sputum isolates and 39/117 (33.3%) bronchoscopy isolates. Sputum from males was more likely to be smear-positive (63.3%) than from females (47.5%). Isolates from lymph node accounted for 136 (17.7%) of all cases; only 28.7 per cent were smear-positive. Eighty-four (11.0%) isolates, comprising 82 M. tuberculosis and 2 M. bovis strains, demonstrated in vitro resistance to at least one of the standard anti-TB medications. Resistance to at least isoniazid and rifampicin (defined as multidrug-resistant TB) was observed for only 8 (1.0%) strains, a rate similar to previous years. Almost all (96.3%) of patients with drug resistant strains were classified as having initial resistance. The country of birth was known for 76 (92.7%) of 82 patients with a drug resistant strain of M. tuberculosis; 6 were Australian-born and 70 (92.1%) had migrated from a total of 17 countries. Of these 70 migrants with drug-resistant disease, 68.6 per cent had migrated from one of the following countries: Vietnam (n=15), China (n=11), Philippines (n=11), India (n=6), and Indonesia (n=5).

Adolescent↗