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Biomedical subjects

J A Halliday

Publications and source records attributed to J A Halliday.

At least 19 recordsLinked to original sources
PubMed2000

Host-specificity of monogenean (platyhelminth) parasites: a role for anterior adhesive areas?

Monogeneans (flatworms) are among the most host-specific of parasites in general and may be the most host-specific of all fish parasites. Specificity, in terms of a restricted spatial distribution within an environment, is not unique to parasites and is displayed by some fungi, insects, birds, symbionts and pelagic larvae of free-living marine invertebrates. The nature of cues, how "habitats" are recognised and how interactions between partners are mediated and maintained is of interest across these diverse "associations". We review some experiments that demonstrate important factors that contribute to host-specificity at the level of infective stages (larvae of oviparous monogeneans; juveniles of viviparous gyrodactylids) and adult parasites. Recent research on immune responses by fish to monogenean infections is considered. We emphasise the critical importance of host epidermis to the Monogenea. Monogeneans live on host epidermis, they live in its products (e.g. mucus), monopisthocotyleans feed on it, some of its products are "attractants" and it may be an inhospitable surface because of its immunological activity. We focus attention on fish but reference is made to amphibian hosts. We develop the concept for a potential role in host-specificity by the anterior adhesive areas, either the specialised tegument and/or anterior secretions produced by monogeneans for temporary but firm attachment during locomotion on host epithelial surfaces. Initial contact between the anterior adhesive areas of infective stages and host epidermis may serve two important purposes. (1) Appropriate sense organs or receptors on the parasite interact with a specific chemical or chemicals or with surface structures on host epidermis. (2) A specific but instant recognition or reaction occurs between component(s) of host mucus and the adhesive(s) secreted by monogeneans. The chemical composition of fish skin is known to be species-specific and our preliminary analysis of the chemistry of some monogenean adhesives indicates they are novel proteins that display some differences between parasite families and species.

Animals↗
PubMed2000

Preparation and characterization of polyclonal antibodies against human chaperonin 10.

Early pregnancy factor (EPF) has been identified as an extracellular homologue of chaperonin 10 (Cpn10), a heat shock protein that functions within the cell as a molecular chaperone. Here, we report the production of polyclonal antibodies directed against several different regions of the human Cpn10 molecule and their application to specific protein quantitation and localization techniques. These antibodies will be valuable tools in further studies to elucidate the mechanisms underlying the differential spatial and temporal localization of EPF and Cpn10 and in studies to elucidate structure and function.

Amino Acid Sequence↗
PubMed1997

Genetic analysis of mutagenesis in aging Escherichia coli colonies.

Bacteria live in unstructured and structured environments, experiencing feast and famine lifestyles. Bacterial colonies can be viewed as model structured environments. SOS induction and mutagenesis have been observed in aging Escherichia coli colonies, in the absence of exogenous sources of DNA damage. This cAMP-dependent mutagenesis occurring in Resting Organisms in a Structured Environment (ROSE) is unaffected by a umuC mutation and therefore differs from both targeted UV mutagenesis and recA730 (SOS constitutive) untargeted mutagenesis. As a recB mutation has only a minor effect on ROSE mutagenesis it also differs from both adaptive reversion of the lacI33 allele and from iSDR (inducible Stable DNA Replication) mutagenesis. Besides its recA and lexA dependence, ROSE mutagenesis is also uvrB and polA dependent. These genetic requirements are reminiscent of the untargeted mutagenesis in lambda phage observed when unirradiated lambda infects UV-irradiated E. coli. These mutations, which are not observed in aging liquid cultures, accumulate linearly with the age of the colonies. ROSE mutagenesis might offer a good model for bacterial mutagenesis in structured environments such as biofilms and for mutagenesis of quiescent eukaryotic cells.

Bacterial Proteins↗
PubMed1995

Editing DNA replication and recombination by mismatch repair: from bacterial genetics to mechanisms of predisposition to cancer in humans.

A hereditary form of colon cancer, hereditary non-polyposis colon cancer (HNPCC), is characterized by high instability of short repeated sequences known as microsatellites. Because the genes controlling microsatellite stability were known in bacteria and yeast, as was their evolutionary conservation, the search for human genes responsible for HNPCC became a 'targeted' search for known sequences. Mismatch-repair deficiency in bacteria and yeast produces multiple phenotypes as a result of its dual involvement in the editing of both replication errors and recombination intermediates. In addition, mismatch-repair functions are specialized in eukaryotes, characterized by specific mitotic (versus meiotic) functions, and nuclear (versus mitochondrial) localization. Given the number of phenotypes observed so far, we predict other links between mismatch-repair deficiency and human genetic disorders. For example, a similar type of sequence instability has been found in HNPCC tumours and in a number of neuro-muscular genetic disorders. Several human mitochondrial disorders display genomic instabilities reminiscent of yeast mitochondrial mismatch-repair mutants. In general, the process of mismatch repair is responsible for the constant maintenance of genome stability and its faithful transmission from one generation to the next. However, without genetic alteration, species would not be able to adapt to changing environments. It appears that nature has developed both negative and positive controls for genetic diversity. In bacteria, for example, an inducible system (sos) exists which generates genetic alterations in response to environmental stress (e.g. radiation, chemicals, starvation). Hence, the cost of generating diversity to adapt to changing conditions might be paid as sporadic gene alterations associated with disease.

Amino Acid Sequence↗
PubMed1995

Inversions with deletions and duplications.

Complex mutational events, including de novo inversion with deletion and duplication of sequence, have been observed but are difficult to model. We propose that nascent leading-strand misalignment upon the lagging-strand template during DNA replication can result in the inversion of sequence. The positioning of this misalignment and of the realignment of the leading strand back into the leading-strand template will determine if the inversion is accompanied by deletion and duplication of sequence. We suggest that such strand misalignment-realignment events may occur at the replication fork during concurrent DNA replication.

Base Sequence↗
PubMed1995

Parental asthma knowledge: its association with readmission of children to hospital.

OBJECTIVE: To assess whether poor parental knowledge about asthma was a risk factor for readmission of their children to hospital. METHODOLOGY: Parents of children who were admitted to the paediatric facility at Newcastle Mater and John Hunter Hospitals were administered a previously validated asthma knowledge questionnaire with a maximum possible score of 31. RESULTS: The mean parental knowledge scores for three groups of children were determined: those with a previous diagnosis of asthma being readmitted to hospital (170 children, mean score 18.3); those with a previous diagnosis of asthma being admitted for the first time (114 children, mean score 17.2); and children being admitted with their first attack of asthma (65 children, mean score 15.6). There was a significant difference in parental asthma knowledge between the first and third group (P < 0.001) but not between the first and second group. A linear regression model with knowledge score as an outcome found that increased knowledge was associated with previously diagnosed asthma, higher parental occupation and no smoker in the home. CONCLUSIONS: Knowledge was poor in all groups. Readmission rate was related to the severity of the child's asthma.

Adolescent↗
PubMed1995

Teacher initiated improvement of asthma policy in schools.

OBJECTIVE: To assess whether information about asthma acquired by individual teachers, following attendance at an inservice seminar, would be communicated to other school staff, and whether policies about asthma management would be subsequently developed in schools. METHODOLOGY: A telephone interview was conducted of 50 primary school teachers in the Hunter Region who were selected randomly from those who had represented their school at an inservice seminar about asthma. RESULTS: All 48 respondents had provided feedback to their colleagues, mostly at a staff meeting. After the seminar the number of schools with a written policy about the management of asthma had increased from 1 to 20. Initially the school's first aid kits contained a bronchodilator inhaler in 25 schools (increasing to 43 after the seminar), a spacer device in six schools (increasing to 47) and written guidelines for management of an asthma attack in seven schools (increasing to 32). Teachers from four schools indicated that all school staff knew how to recognize an acute attack prior to the seminar compared with 22 schools afterwards. Before the seminar 18 schools asked parents to supply written instructions for the management of their children at school but this increased to 44 after the seminar. CONCLUSIONS: A programme of one-off seminars attended by one teacher from each primary school resulted in large increases in the proportion of schools with appropriate policies for the management of asthma in the school environment.

Asthma↗
PubMed1994

Headache and asthma.

The aim of this study was to investigate the association between headache and asthma, bronchodilators and atopy in school children. A cross-sectional survey of all primary school children was conducted in two towns near Newcastle, New South Wales, Australia; one in the vicinity of two coal-fired power stations, the other free of outdoor industrial air pollution. The main outcome measures were frequent headache, wheezing, bronchial reactivity, use of bronchodilators and atopy. Eight hundred and fifty-one primary school children aged 5-12 years participated (92% response rate). Twenty-three per cent of the children were reported to have had a history of frequent headache. Crude odds ratios indicated that the odds of frequent headache was significantly higher in children with asthma and atopy and where there was a smoker in the home, but that there was no association between frequent headache and use of bronchodilators or the sex of the child or socio-economic status measured as father's occupation. Stepwise logistic regression with frequent headache as the outcome of interest showed that, after adjusting for age and smoking in the home, the odds ratio for asthma (defined as current wheeze) was 3.24 (95% confidence interval [CI] 2.19-4.77). The similarly adjusted odds ratio for asthma defined as bronchial hyperreactivity (BHR) was 1.60 (95% CI 1.09-2.37). Atopy was not statistically significantly associated with headache for either model. Asthma (defined as wheeze or BHR) is an independent risk factor for frequent headache. The relationship between headache and asthma is an association with bronchial hyperresponsiveness rather than atopy.

Age Factors↗
PubMed1994

Two hour seminar improves knowledge about childhood asthma in school staff.

Teachers and support staff are often called upon to manage asthma at school but may have little knowledge and understanding of the condition. The aim of this study was to determine whether a short seminar would improve knowledge in non-health professionals. Seventy school staff attended one of five 2 h seminars presented by an asthma educator. Participants completed the Newcastle Asthma Knowledge Questionnaire (AKQ) before, and 2 months after, the seminar. The mean initial score (maximum possible 31) was 16.4 (range 4-26), increasing to 23 (range 13-29, P = 0.0001). There was a large increase in knowledge about symptoms, pathophysiology, preventive medications and side effects of medications. Initially almost all of the participants had deficiencies in knowledge about reliever medications and the management of exercise-induced asthma. After the seminar, knowledge in these areas was still poor, with only one-third of the participants answering them correctly. The results have been used to modify the content of the 2 h seminar with increased emphasis on those areas in which deficiencies in knowledge were demonstrated. No data are available yet as to whether this improved knowledge has improved management.

Age of Onset↗
PubMed1994

The management of epiglottitis in a small paediatric intensive care unit.

The aim of this study was to examine the outcome of epiglottitis in a small paediatric institution. Over the 5 year period October 1986 to September 1991, 44 children (of whom 15 were retrieved) with epiglottitis were admitted to the only paediatric intensive care facility in the Hunter Region. The so-called classical features were often absent. Forty of the 44 children were intubated. The mean length of intubation was 22 h and the mean length of hospital stay was only 2 1/2 days. One child had a respiratory arrest prior to intubation but made a complete recovery; one child had a coexistent submental/submandibular fascial space infection; 16 (36%) had abnormal chest radiographs. Five children had post-extubation stridor with one of these children left with residual hoarseness. Epiglottitis can be managed safely in a small paediatric intensive care unit with acceptable short-term and long-term complications.

Airway Obstruction↗
PubMed1993

Feline and canine milk lysozymes.

1. The electrophoretic characteristics of feline (Felis catus) and canine (Canis familiaris) milk lysozymes were studied using starch gel electrophoresis and isoelectric focusing. 2. Feline milk lysozyme was found to be polymorphic (two variants, designated A and B with frequencies of 0.13 and 0.87, respectively). Canine milk lysozyme was not polymorphic. 3. The lytic activities of feline and canine milk lysozymes were examined in buffers of varying pH and ionic strength. Preliminary kinetics studies were done. 4. Maximal lytic activity for both lysozymes was found in imidazole-HCl buffer pH 7.4 and both exhibited second order reaction kinetics. 5. Amino acid compositions of both lysozymes were determined.

Amino Acids↗
PubMed1993

Mutational specificity of 2-nitro-3,4-dimethylimidazo[4,5-f]quinoline in the lacI gene of Escherichia coli.

2-Nitro-3,4-dimethylimidazo[4,5-f]quinoline (NO2-MeIQ) is the nitro derivative of 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), one of the food pyrolysis product mutagens and carcinogens. The mutational specificity of NO2-MeIQ was determined using the lacI system in an Escherichia coli strain, EE125, harbouring the plasmid pKM101. NO2-MeIQ acts as a direct-acting mutagen towards this strain, and induces a broad range of mutational alterations. At higher doses; G:C-->T:A transversions dominate the mutational spectrum. Complex mutations were also observed, and the involvement of the SOS system in the processing of the mutations induced by NO2-MeIQ is suggested.

Bacterial Proteins↗
PubMed1993

Increased wheeze but not bronchial hyperreactivity near power stations.

STUDY OBJECTIVE: In a previous study a higher than expected prevalence of asthma was found in Lake Munmorah, a coastal town near two power stations, compared with another coastal control town. This study aimed to compare atopy, bronchial hyperreactivity, and reported symptoms of asthma in the power station town and a second control area with greater socioeconomic similarity. DESIGN: A cross sectional survey was undertaken. SETTINGS: Lake Munmorah, a coastal town near two power stations, and Dungog, a country town in the Hunter Valley, NSW, Australia. PARTICIPANTS: All children attending kindergarten to year 6 at all schools in the two towns were invited to participate in 1990. The response rates for the questionnaire for reported symptoms and associated demographic data were 92% in Lake Munmorah and 93% in Dungog, with 84% and 90% of children respectively being measured for lung function, atopy, and bronchial reactivity. There were 419 boys and 432 girls aged 5 to 12 years. MEASUREMENTS AND MAIN RESULTS: Main outcome measures were current wheeze and bronchial hyper-reactivity, defined as a fall in forced expiratory volume in 1 second (FEV1) or peak expiratory flow (PEF) of 20% or more. Current wheeze was reported in 24.8% of the Lake Munmorah children compared with 14.6% of the Dungog children. Bronchial hyper-reactivity was similar for both groups--25.2% in Lake Munmorah and 22.3% in Dungog. The mean baseline FEV1 was lower in Lake Munmorah than in Dungog (p < 0.001). Dungog children were more likely to have positive skin test to house dust mite (Dungog 27.0%, Lake Munmorah 20.2%, p = 0.028) but there were no other differences in skin test atopy in the two towns. After adjusting for age, gender, any smoker in the house, and positive dust mite skin test, the odds of current wheeze in Lake Munmorah compared with Dungog was 2.16 (95% confidence interval 1.45, 3.15). CONCLUSIONS: Baseline lung function was lower and reported symptoms of asthma were higher in the power station town, but bronchial hyper-reactivity and skin test defined atopy were similar in the two communities. These results are consistent with the previous study and confirm the increased presence of reported symptomatic illness in the town near power stations.

Asthma↗
PubMed1993

Short intervention can improve knowledge about childhood asthma in nursing staff.

Twenty-nine community or hospital-based general nurses from the Upper Hunter Valley attended a 3-hr seminar on asthma and completed a previously validated asthma knowledge questionnaire before and 6 weeks after the seminar. The mean initial score (maximum possible 31) was 20.6 [95% confidence interval (CI) 19.1-22.0], which increased at follow-up to 26.2 (95% CI 25.0-27.3). Only 5 of 29 nurses scored 24 or more initially compared with 17 of 21 at follow-up. Even after the seminar, the nurses had major deficiencies in knowledge about preventive medication and the management of exercise-induced asthma.

Asthma↗
PubMed1991

The complete amino acid sequence of feline beta-lactoglobulin II and a partial revision of the equine beta-lactoglobulin II sequence.

The amino acid sequence of feline beta-lactoglobulin (designated II) has been determined. The protein chain is 163 amino acids long with a relative molecular mass of 18,558. The primary structure was determined by sequencing of native protein (residues 1-25), BPNS-skatole cleavage fragments and the peptides obtained by proteolytic cleavage with V8 proteinase and TPCK-trypsin. Feline beta-lactoglobulin II has 53 and 57% positional identities with bovine beta-lactoglobulin A and equine beta-lactoglobulin I, respectively, and approx. 68% with a revised sequence of equine beta-lactoglobulin II. The equine beta-lactoglobulin II sequence was re-examined between positions 78 and 122 resulting in a major revision in this area with only a single insertion to give a total of 163 residues.

Amino Acid Sequence↗
PubMed1991

Spontaneous and 9-aminoacridine-induced frameshift mutagenesis: second-site frameshift mutation within the N-terminal region of the lacI gene of Escherichia coli.

A novel forward mutational system, based on the acquisition of an Iq-d dominant phenotype from an initial Iq- recessive state, was used to identify second-site frameshift mutation [+/- 1(+/- 3n) events] within the N-terminal region of the lacI gene of Escherichia coli. The DNA sequences are described of forty-six spontaneous and twenty 9-aminoacridine(9-AA)-induced second site mutations. Although -1 frameshift events dominate both spectra, the nature and site specificity of these events clearly distinguish two mutational distributions. The spontaneous distribution contains two -(A:T) frameshift hotspots; one within a monotonic A5 run (9 occurrences), the other at a 5'-CACAACAAC-3' sequence (12 occurrences). In contrast 17 of the 20 mutations recovered after 9-AA treatment involve the loss of a G:C pair, 14 of which occur at a single site (5'-CGGGC-3'). The striking specificity of the observed mutational hotspots is of interest since this open genetic target contains similar sequences which were infrequently recovered.

Aminacrine↗