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Biomedical subjects

J Austin

Publications and source records attributed to J Austin.

At least 19 recordsLinked to original sources
PubMed2003

Structural, genetic and functional characterization of the flagellin glycosylation process in Helicobacter pylori.

Mass spectrometry analyses of the complex polar flagella from Helicobacter pylori demonstrated that both FlaA and FlaB proteins are post-translationally modified with pseudaminic acid (Pse5Ac7Ac, 5,7-diacetamido-3,5,7,9-tetradeoxy-l-glycero-l-manno -n o n-ulosonic acid). Unlike Campylobacter, flagellar glycosylation in Helicobacter displays little heterogeneity in isoform or glycoform distribution, although all glycosylation sites are located in the central core region of the protein monomer in a manner similar to that found in Campylobacter. Bioinformatic analysis revealed five genes (HP0840, HP0178, HP0326A, HP0326B, HP0114) homologous to other prokaryote genes previously reported to be involved in motility, flagellar glycosylation or polysaccharide biosynthesis. Insertional mutagenesis of four of these homologues in Helicobacter (HP0178, HP0326A, HP0326B, HP0114) resulted in a non-motile phenotype, no structural flagella filament and only minor amounts of flagellin protein detectable by Western immunoblot. However, mRNA levels for the flagellin structural genes remained unaffected by each mutation. In view of the combined bioinformatic and structural evidence indicating a role for these gene products in glycan biosynthesis, subsequent investigations focused on the functional characterization of the respective gene products. A novel approach was devised to identify biosynthetic sugar nucleotide precursors from intracellular metabolic pools of parent and isogenic mutants using capillary electrophoresis-electrospray mass spectrometry (CE-ESMS) and precursor ion scanning. HP0326A, HP0326B and the HP0178 gene products are directly involved in the biosynthesis of the nucleotide-activated form of Pse, CMP-Pse. Mass spectral analyses of the cytosolic extract from the HP0326A and HP0326B isogenic mutants revealed the accumulation of a mono- and a diacetamido trideoxyhexose UDP sugar nucleotide precursor.

Amino Acid Sequence↗
PubMed2002

Provision of postoperative epidural services in NHS hospitals.

To describe facilities for postoperative epidurals in UK National Health Service Hospitals, a questionnaire was sent to each hospital performing surgery below the head and neck. Of 271 hospitals, 256 replied (95%). While almost all offer postoperative epidurals, only 78 (30%) offer them to all surgical disciplines. Most hospitals rely on acute pain nurses for troubleshooting during the day, and on trainee anaesthetists after hours. Administration is most commonly by continuous infusion. There was no restriction on the use of epidural opioids in 67% of hospitals. Most (96%) hospitals have a protocol for epidural care, although the specified level of monitoring varies widely. There is no consensus of practice on removal of epidural catheters relative to anticoagulation. Levels of training in epidural care also vary widely. Two hundred and thirty-six hospitals (92%) have an acute pain team. Despite the expansion in acute pain services, facilities for postoperative epidurals are deficient in many NHS hospitals.

Analgesia, Epidural↗
PubMed2002

Sexual transmission risk perceptions and behavioural correlates of HIV concentrations in semen.

HIV transmission risk behaviours are related to perceived infectiousness and HIV-positive men who have undetectable blood viral loads may practise less protective behaviours. The current study extends previous research by reporting the association between perceived HIV transmission risks, risk behaviours and viral load in semen. Results showed significant associations between perceived risks for transmitting HIV, unprotected intercourse and viral load in semen. Further analyses showed that men with greater concentrations of HIV in their semen were practising higher rates of transmission risk behaviours while perceiving less risk for potentially transmitting HIV. We conclude that behavioural interventions are needed for HIV-positive men to inform them that HIV infectiousness cannot be inferred from peripheral blood viral loads and to support maintenance of HIV risk reduction behaviours.

Attitude to Health↗
PubMed2001

Human immunodeficiency virus in semen and plasma: investigation of sexual transmission risk behavioral correlates.

Risks for sexually transmitted HIV may be related to concentrations of virus detected in semen and previous research shows a small to moderate association between viral load in blood and semen. This study examined the association between viral load in semen and plasma in a community sample of HIV-infected men and is the first study to examine semen viral load in relation to sexual transmission risk behaviors. A sample of 44 HIV-positive men recruited from community service agencies provided semen, blood, and urine samples and completed clinical interviews assessing health and behavior. We failed to find an association between viral load in semen and plasma, Spearman rho = 0.07, p > 0.1. When restricted to participants with detectable virus in semen and plasma, the correlation remained nonsignificant, rho = -0.16, p > 0.1. Men who had higher semen viral loads relative to their plasma viral load were distinguished by having engaged in significantly higher rates of unprotected intercourse as the insertive sex partner in the previous 3 months. Semen viral load was not, however, related to recent or current sexually transmitted infections (STIs). This study is among the first to examine sexual transmission risk behaviors as marker for HIV infectiousness. Results caution against inferring sexual transmission infectiousness based on plasma viral load and suggest that HIV-positive men who practice higher rates of insertive intercourse may be more infectious even in the absence of other STIs.

Adult↗
PubMed2001

Complete mitochondrial genome sequences of two extinct moas clarify ratite evolution.

The origin of the ratites, large flightless birds from the Southern Hemisphere, along with their flighted sister taxa, the South American tinamous, is central to understanding the role of plate tectonics in the distributions of modern birds and mammals. Defining the dates of ratite divergences is also critical for determining the age of modern avian orders. To resolve the ratite phylogeny and provide biogeographical data to examine these issues, we have here determined the first complete mitochondrial genome sequences of any extinct taxa--two New Zealand moa genera--along with a 1,000-base-pair sequence from an extinct Madagascan elephant-bird. For comparative data, we also generated 12 kilobases of contiguous sequence from the kiwi, cassowary, emu and two tinamou genera. This large dataset allows statistically precise estimates of molecular divergence dates and these support a Late Cretaceous vicariant speciation of ratite taxa, followed by the subsequent dispersal of the kiwi to New Zealand. This first molecular view of the break-up of Gondwana provides a new temporal framework for speciation events within other Gondwanan biota and can be used to evaluate competing biogeographical hypotheses.

Animals↗
PubMed2001

Effectiveness of an intervention to reduce HIV transmission risks in HIV-positive people.

BACKGROUND: As many as one in three HIV-positive people continue unprotected sexual practices after learning that they are HIV infected. This article reports the outcomes of a theory-based intervention to reduce risk of HIV transmission for people living with HIV infection. METHODS: Men (n=233) and women (n=99) living with HIV-AIDS were randomly assigned to receive either (1) a five-session group intervention focused on strategies for practicing safer sexual behavior, or (2) a five-session, contact-matched, health-maintenance support group (standard-of-care comparison). Participants were followed for 6 months post-intervention. RESULTS: The intervention to reduce risk of HIV transmission resulted in significantly less unprotected intercourse and greater condom use at follow-up. Transmission-risk behaviors with non-HIV-positive sexual partners and estimated HIV transmission rates over a 1-year horizon were also significantly lower for the behavioral risk-reduction intervention group. CONCLUSIONS: This study is among the first to demonstrate successful HIV-transmission risk reduction resulting from a behavioral intervention tailored for HIV-positive men and women.

Adaptation, Psychological↗
PubMed2001

An evaluation of standard retrieval algorithms and a binary neural approach.

In this paper we evaluate a selection of data retrieval algorithms for storage efficiency, retrieval speed and partial matching capabilities using a large Information Retrieval dataset. We evaluate standard data structures, for example inverted file lists and hash tables, but also a novel binary neural network that incorporates: single-epoch training, superimposed coding and associative matching in a binary matrix data structure. We identify the strengths and weaknesses of the approaches. From our evaluation, the novel neural network approach is superior with respect to training speed and partial match retrieval time. From the results, we make recommendations for the appropriate usage of the novel neural approach.

Algorithms↗
PubMed2001

Creation of low-copy integrated transgenic lines in Caenorhabditis elegans.

In Caenorhabditis elegans, transgenic lines are typically created by injecting DNA into the hermaphrodite germline to form multicopy extrachromosomal DNA arrays. This technique is a reliable means of expressing transgenes in C. elegans, but its use has limitations. Because extrachromosomal arrays are semistable, only a fraction of the animals in a transgenic extrachromosomal array line are transformed. In addition, because extrachromosomal arrays can contain hundreds of copies of the transforming DNA, transgenes may be overexpressed, misexpressed, or silenced. We have developed an alternative method for C. elegans transformation, using microparticle bombardment, that produces single- and low-copy chromosomal insertions. Using this method, we find that it is possible to create integrated transgenic lines that reproducibly express GFP reporter constructs without the variations in expression level and pattern frequently exhibited by extrachromosomal array lines. In addition, we find that low-copy integrated lines can also be used to express transgenes in the C. elegans germline, where conventional extrachromosomal arrays typically fail to express due to germline silencing.

Animals↗
PubMed2001

Interactions and nuclear import of the N and P proteins of sonchus yellow net virus, a plant nucleorhabdovirus.

We have characterized the interaction and nuclear localization of the nucleocapsid (N) protein and phosphoprotein (P) of sonchus yellow net nucleorhabdovirus. Expression studies with plant and yeast cells revealed that both N and P are capable of independent nuclear import. Site-specific mutagenesis and deletion analyses demonstrated that N contains a carboxy-terminal bipartite nuclear localization signal (NLS) located between amino acids 465 and 481 and that P contains a karyophillic region between amino acids 40 and 124. The N NLS was fully capable of functioning outside of the context of the N protein and was able to direct the nuclear import of a synthetic protein fusion consisting of green fluorescent protein fused to glutathione S-transferase (GST). Expression and mapping studies suggested that the karyophillic domain in P is located within the N-binding domain. Coexpression of N and P drastically affected their localization patterns relative to those of individually expressed proteins and resulted in a shift of both proteins to a subnuclear region. Yeast two-hybrid and GST pulldown experiments verified the N-P and P-P interactions, and deletion analyses have identified the N and P interacting domains. N NLS mutants were not transported to the nucleus by import-competent P, presumably because N binding masks the P NLS. Taken together, our results support a model for independent entry of N and P into the nucleus followed by associations that mediate subnuclear localization.

Cell Nucleus↗
PubMed2000

Sites of aggrecan cleavage by recombinant human aggrecanase-1 (ADAMTS-4).

Aggrecan, the major proteoglycan of cartilage that provides its mechanical properties of compressibility and elasticity, is one of the first matrix components to undergo measurable loss in arthritic diseases. Two major sites of proteolytic cleavage have been identified within the interglobular domain (IGD) of the aggrecan core protein, one between amino acids Asn(341)-Phe(342) which is cleaved by matrix metalloproteinases and the other between Glu(373)-Ala(374) that is attributed to aggrecanase. Although several potential aggrecanase-sensitive sites had been identified within the COOH terminus of aggrecan, demonstration that aggrecanase cleaved at these sites awaited isolation and purification of this protease. We have recently cloned human aggrecanase-1 (ADAMTS-4) (Tortorella, M. D., Burn, T. C., Pratta, M. A., Abbaszade, I., Hollis, J. M., Liu, R., Rosenfeld, S. A., Copeland, R. A., Decicco, C. P., Wynn, R., Rockwell, A., Yang, F., Duke, J. L., Solomon, K., George, H., Bruckner, R., Nagase, H., Itoh, Y., Ellis, D. M., Ross, H., Wiswall, B. H., Murphy, K., Hillman, M. C., Jr., Hollis, G. F., Newton, R. C., Magolda, R. L., Trzaskos, J. M., and Arner, E. C. (1999) Science 284, 1664-1666) and herein demonstrate that in addition to cleavage at the Glu(373)-Ala(374) bond, this protease cleaves at four sites within the chondroitin-sulfate rich region of the aggrecan core protein, between G2 and G3 globular domains. Importantly, we show that this cleavage occurs more efficiently than cleavage within the IGD at the Glu(373)-Ala(374) bond. Cleavage occurred preferentially at the KEEE(1667-1668)GLGS bond to produce both a 140-kDa COOH-terminal fragment and a 375-kDa fragment that retains an intact G1. Cleavage also occurred at the GELE(1480-1481)GRGT bond to produce a 55-kDa COOH-terminal fragment and a G1-containing fragment of 320 kDa. Cleavage of this 320-kDa fragment within the IGD at the Glu(373)-Ala(374) bond then occurred to release the 250-kDa BC-3-reactive fragment from the G1 domain. The 140-kDa GLGS-reactive fragment resulting from the preferential cleavage was further processed at two additional cleavage sites, at TAQE(1771)-(1772)AGEG and at VSQE(1871-1872)LGQR resulting in the formation of a 98-kDa fragment with an intact G3 domain and two small fragments of approximately 20 kDa. These data elucidate the sites and efficiency of cleavage during aggrecan degradation by aggrecanase and suggest potential tools for monitoring aggrecan cleavage in arthritis.

ADAM Proteins↗
PubMed2000

High-performance affinity chromatography and immobilized serum albumin as probes for drug- and hormone-protein binding.

The binding of drugs and hormones to proteins within the blood is an important process in determining the transport, excretion, metabolism and activity of such agents. This paper discusses the combined use of immobilized serum albumin and high-performance affinity chromatography (HPAC) as tools for the study of such binding processes. The general approaches that are used in such work and are illustrated by several examples taken from previous work in the author's laboratory. The type of qualitative and quantitative information that can be obtained by such work is described, including the comparison of relative binding affinities, competitive displacement by other agents or the measurement of equilibrium and rate constants based on immobilized albumin columns. A comparison is also provided between the results that are obtained by these methods and those that are provided by solution-phase albumin. Some newer advances that are highlighted include use of HPAC to examine the binding of non-polar compounds to albumin, the effects of binding site heterogeneity on HPAC measurements and the use of chemically-modified albumin as a tool to examined the site-specific interactions of solutes with albumin.

Binding, Competitive↗
PubMed2000

Why the high rate of dropout from individualized cognitive-behavior therapy for bulimia nervosa?

OBJECT: To investigate predictors of dropout from cognitive-behavior therapy for bulimia nervosa. METHOD: Pretreatment assessment measures were examined including the Eating Disorder Inventory-2, Body Satisfaction Questionnaire, Beck Depression Inventory, Beck Hopelessness Scale, the Locus of Control of Behavior Scale, and demographic and behavioral measures. RESULTS: Forty-three percent (n = 14) of clients with a DSM-IV diagnosis of bulimia nervosa dropped out of treatment prematurely. No differences were found between treatment completers and dropouts with respect to the initial severity of bulimia-related symptoms. Noncompleters were, however, found to have significantly higher depression and hopelessness scores as well as elevated levels of external locus of control. Discriminate analysis showed that these variables resulted in a 90% prediction accuracy of individuals who prematurely dropped out of treatment. DISCUSSION: Results suggest a need to focus treatment directly on factors such as hopelessness and depression in addition to standard bulimia procedures to ensure clients are able to engage in therapy.

Adolescent↗
PubMed2000

Cheap, accurate and rapid allele frequency estimation of single nucleotide polymorphisms by primer extension and DHPLC in DNA pools.

At present, the cost of genotyping single nucleotide polymorphisms (SNPs) in large numbers of subjects poses a formidable problem for molecular genetic approaches to complex diseases. We have tested the possibility of using primer extension and denaturing high performance liquid chromatography to estimate allele frequencies of SNPs in pooled DNA samples. Our data show that this method should allow the accurate estimation of absolute allele frequencies in pooled samples of DNA and also of the difference in allele frequency between different pooled DNA samples. This technique therefore offers an efficient and cheap method for genotyping SNPs in large case-control and family-based association samples.

Alleles↗