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Biomedical subjects

J Harrison

Publications and source records attributed to J Harrison.

At least 127 records · Page 7Linked to original sources
PubMed1995

CpNpG methylation in mammalian cells.

In vertebrate DNA, 3% to 5% of cytosine residues are present as 5-methylcytosine, and it is generally accepted that essentially all of this methylation occurs at cytosines which are contained in the symmetrical dinucleotide CpG. In this report we demonstrate, using bisulphite genomic sequencing, that the methylation machinery of mammalian cells is capable of both maintenance and de novo methylation at CpNpG sites. The existence of inherited CpNpG methylation in mammalian cells has important implications in gene regulation and in the aetiology of disease.

3T3 Cells↗
PubMed1995

Factors associated with sexual functioning in women following spinal cord injury.

Research into sexuality following spinal cord injury (SCI) has tended to concentrate on male experiences and the physical capabilities for sexual intercourse. The sexuality of women following SCI has only recently been addressed and studies are limited to small numbers and the use of non-standardised measures. The present investigation utilised standard measures of affective state and body satisfaction together with pre and post-injury questionnaire information of sexual dysfunction, feelings about sex and importance of sexual activity in a group of 85 women with SCI. Sexual dysfunction increased significantly post-injury, whilst feelings about sex and it's importance were unaffected. Sexual dysfunction and the importance of sex were inversely correlated. General and Head satisfaction estimates were not significantly different to control samples, whilst Body Satisfaction was increased for women with disabilities. None of the body satisfaction measures were related to the sexual functioning measure. General dissatisfaction was associated depression. Both anxiety and depression were experienced by the same individuals, and anxiety related to current sexual dysfunction. Qualitative data supported previous findings concerning the effects of social and attitudinal barriers on sexual functioning.

Adolescent↗
PubMed1995

The physiology of coloured hearing. A PET activation study of colour-word synaesthesia.

In a small proportion of the normal population, stimulation in one modality can lead to perceptual experience in another, a phenomenon known as synaesthesia. In the most common form of synaesthesia, hearing a word can result in the experience of colour. We have used the technique of PET, which detects brain activity as changes of regional cerebral blood flow (rCBF), to study the physiology of colour-word synaesthesia in a group of six synaesthete women. During rCBF measurements synaesthetes and six controls were blindfolded and were presented with spoken words or pure tones. Auditory word, but not tone, stimulation triggered synaesthesia in synaesthetes. In both groups word stimulation compared with tone stimulation activated the classical language areas of the perisylvian regions. In synaesthetes, a number of additional visual associative areas, including the posterior inferior temporal cortex and the parieto-occipital junctions, were activated. The former has been implicated in the integration of colour with shape and in verbal tasks which require attention to visual features of objects to which words refer. Synaesthetes also showed activations in the right prefrontal cortex, insula and superior temporal gyrus. By contrast, no significant activity was detected in relatively lower visual areas, including areas V1, V2 and V4. These results suggest that colour-word synaesthesia may result from the activity of brain areas concerned with language and visual feature integration. In the case of colour-word synaesthesia, conscious visual experience appears to occur without activation of the primary visual cortex.

Adult↗
PubMed1995

Human parvovirus B19 infection in healthcare workers.

This paper reports the occurrence of human parvovirus B19 infection in seven healthcare workers in an acute hospital. The clinical presentation mimicked that of rubella and the diagnosis was made by the detection of human parvovirus B19 IgM antibody in blood samples taken from the affected members of staff. The paper discusses the importance of accurate diagnosis of B19 infection because this virus has been implicated in causing or exacerbating a variety of medical conditions. B19 infection may be serious for people with chronic haemolytic anaemias, those who are immunocompromised or those who are pregnant. B19 infection in pregnancy may be a cause of hydrops fetalis, particularly if the infection occurs during the second trimester. This is in contrast to the risk of intra-uterine rubella infection which is maximal in the first few weeks of pregnancy and which affects fetal development. The paper highlights the need for guidelines for occupational health practitioners on the management of parvovirus B19 infection and the need to make healthcare workers aware of the importance of this infection.

Adult↗
PubMed1995

From paradigms lost to paradigms regained? The MILTON approach to health care reform.

Proposes the MILTON model of health care policy and management as a framework within which debates about the future reform of the UK National Health Service may be conducted. Reviews the economic, political, social and technological forces which have shaped health care policy and management. Suggests that, at the macrolevel, the paradigm has changed from one based on assessment of needs to one based on securing value for money. At the microlevel, there have been equally profound changes in the nature and availability of work. A theme common to both levels is that of rapid and continuous change. Claims the MILTON model offers a way for the protagonists in the health care debate to locate their arguments about policies of health care provision and the implications for the management of work in a changing world in four planes of the model. The benefits are that the differing positions may be seen more clearly and, arguably more important, that a wider range of options is appreciated when, all too often in the past, arguments have become polarized on a single plane.

Decision Making, Organizational↗
PubMed1995

Work-related deaths of children and adolescents in Australia, 1982 to 1984.

Work-related deaths of children and adolescents up to the age of 19 years were studied as part of a larger investigation into all work-related fatalities in Australia in the three-year period, 1982 to 1984. This study aimed to characterise the circumstances which led to the deaths of these children. Of 1738 work-related fatalities identified over the three years in the larger investigation, 67 (4 per cent) were aged under 15 years, and 117 (7 per cent) were aged 15 to 19 years. The fatalities were characterised by a number of variables, the most important being age, sex, bystander status, location (farm or other) and vehicle involvement (especially tractors). The causes of death differed between subgroups. Although existing controls may be reasonably effective in minimising child deaths in most work places, farms are an exception. On farms, home and work activities overlap, and informal participation in work by the young is quite common. Preventive efforts should give special attention to farms and tractors, to toddlers and male children, and to measures (such as safety devices and other external control measures) which do not rely on behavioural change in the young people at risk. Adults responsible for young children should be educated to anticipate dangerous situations and thus ensure children are protected from injury hazards.

Accidents, Occupational↗
PubMed1995

Abnormal refractoriness in patients with Parkinson's disease after brief withdrawal of levodopa treatment.

Two pairwise matched groups of patients with mild to moderate Parkinson's disease and a group of normal age matched controls were used to investigate the effects on simple and choice reaction time (RT) of brief withdrawal of levodopa therapy. Comparisons within and across these groups disclosed a selective effect of levodopa withdrawal. After about 12 hours of levodopa deprivation, patients exhibited an exaggeration of normal refractoriness, the well established tendency for RT to increase progressively as the delay between a response and the next imperative signal is reduced below 0.5 s. Increased refractoriness was at least as great for simple as choice RT. Choice RT on trials involving repetition (as opposed to alternation) of the previous response, however, showed no tendency towards greater impairment by brevity of the recovery period or by withdrawal of medication, eliminating an effector based account. With longer recovery periods, RT was unaffected by medication; indeed, unmedicated patients were as fast as normal subjects under these conditions. Even at the briefest delays, fully medicated patients did not differ from normal controls. The paper concludes with a critical review of chronometric studies of medication effects in Parkinson's disease.

Analysis of Variance↗
PubMed1995

Analysis of violent incidents in a regional secure unit.

This study examined violent incidents occurring over a four-year period in a Regional Secure Unit. Data were collected from incident reports and case notes. Patients referred from district general psychiatric hospitals because of unmanageable behaviour were over-represented among the small number of patients who were responsible for the majority of incidents. Most patients exhibited little or no aggression. Seclusion was found unnecessary in the management of such patients. Suggestions for further research in this area are made.

Adult↗
PubMed1995

Social deprivation and psychiatric admission rates among different diagnostic groups.

BACKGROUND: In the search for population-based indicators of need for mental health services, psychiatric admission rates have been correlated with sociodemographic variables. We explored such correlations for different diagnostic groups. METHOD: Admissions data for the 19 districts in the North West Region were derived from the Korner Episode System for 1992/93 and divided into eight broad diagnostic groups using ICD-9 codes. Admission rates per 1000 were correlated with measures of deprivation derived from the 1991 census data and with standardised mortality ratios. For the two largest diagnostic groups, correlations with age-standardised admission rates were also calculated. RESULTS: For schizophrenia/delusional disorder, eight of the 10 sociodemographic measures were significantly correlated with admission rates (Pearson's r 0.52 - 0.79). On all measures these correlations were greater than those seen for total mental illness. Significant positive correlations of a lower order were seen for organic brain syndromes and mania. Admission rates for depression, personality disorder and substance misuse were not significantly correlated with any of the sociodemographic measures. Admission rates for neurotic illness were negatively correlated with all deprivation measures, with the negative correlation statistically significant at the 5% level for ethnic composition and overcrowding. Standardising admission rates for age and repeating the analysis after removal of influential data points did not greatly alter these findings. CONCLUSIONS: The association between psychiatric admission rates and measures of deprivation varies considerably with diagnosis. Measures of social deprivation may indicate need for services for patients with psychotic disorders; admission rates for non-psychotic illnesses may reflect the availability of beds rather than need.

Adolescent↗
PubMed1995

Acid-base status and spiracular control during discontinuous ventilation in grasshoppers

Many insects ventilate discontinuously when quiescent, exhibiting prolonged periods during which little or no gas exchange occurs. We investigated the consequences of discontinuous ventilation (DV) on haemolymph acid­base status and tested whether spiracular opening during DV is due to changes in internal gas tensions in the western lubber grasshopper Taeniopoda eques. At 15 °C, resting T. eques exhibited interburst periods of about 40 min. During the interburst period, haemolymph PCO2 rose from 1.8 to 2.26 kPa, with minimal acidification of haemolymph. Animals in atmospheres in which PCO2 was 2 kPa or below continued to exhibit DV, while atmospheres in which PCO2 was 2.9 kPa or above caused cessation of DV. These data indicate that accumulation of internal CO2 to threshold levels between 2 and 2.9 kPa induces spiracular opening in grasshoppers. In contrast to the situation in lepidopteran pupae, variation in atmospheric PO2 had no effect on interburst duration. Relative to lepidopteran pupae, the internal PCO2 of grasshoppers during DV is threefold lower, the PCO2 required for triggering spiracular opening is also threefold lower, and the open phase spiracular conductance is at least tenfold higher, demonstrating that considerable diversity exists in these aspects of insect respiratory physiology.

Journal Article↗
PubMed1995

The effect of regular sunscreen use on vitamin D levels in an Australian population. Results of a randomized controlled trial.

BACKGROUND AND DESIGN: Studies published have suggested a possibility that regular use of sunscreen to prevent skin cancer may put the population, particularly elderly people, at risk of vitamin D deficiency. We aimed to determine whether regular use of sunscreens in the normal adult population, as recommended by public health authorities for the prevention of skin cancer, may put individuals at risk of vitamin D deficiency. A randomized double-blind control trial of the daily use of a broad-spectrum sunscreen (sun protection factor [SPF] 17) vs placebo cream over a summer period in Australia was conducted in 113 people aged 40 years and over, with sampling stratified by age. All participants had at least one solar keratosis. Serum samples taken at the beginning and at the end of the study were analyzed for 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3. RESULTS: Mean levels of 25-hydroxyvitamin D3 rose significantly by the same amount in both groups over the period of the study (placebo, +12.8 mmol/L; sunscreen, +11.8 mmol/L). Mean levels of 1,25-dihydroxyvitamin D3 increased significantly in the placebo group only (placebo, +10.8 pmol/L; sunscreen, +1.3 pmol/L), but for no subject in either group was the level of 1,25-dihydroxyvitamin D3 outside the reference range either at the start or at the end of the study. There were no significant differences by age, sex, and skin type in the change in 25-hydroxyvitamin D3 or 1,25-dihydroxyvitamin D3 over the study period. CONCLUSIONS: No person, including those aged 70 years and over, developed any vitamin D levels outside the normal reference range during the period of the study. The data suggest that over an Australian summer sufficient sunlight is received, probably through both the sunscreen itself and the lack of total skin cover at all times, to allow adequate vitamin D production in people who are recommended to use sunscreens regularly. More work is required to elucidate the relationship between 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3, particularly during the different seasons of the year.

Adult↗
PubMed1994

High sensitivity mapping of methylated cytosines.

An understanding of DNA methylation and its potential role in gene control during development, aging and cancer has been hampered by a lack of sensitive methods which can resolve exact methylation patterns from only small quantities of DNA. We have now developed a genomic sequencing technique which is capable of detecting every methylated cytosine on both strands of any target sequence, using DNA isolated from fewer than 100 cells. In this method, sodium bisulphite is used to convert cytosine residues to uracil residues in single-stranded DNA, under conditions whereby 5-methylcytosine remains non-reactive. The converted DNA is amplified with specific primers and sequenced. All the cytosine residues remaining in the sequence represent previously methylated cytosines in the genome. The work described has defined procedures that maximise the efficiency of denaturation, bisulphite conversion and amplification, to permit methylation mapping of single genes from small amounts of genomic DNA, readily available from germ cells and early developmental stages.

5-Methylcytosine↗
PubMed1994

Xenopus laevis ovarian DNA helicase I: A 3' to 5' helicase that unwinds short duplexes.

A novel DNA helicase isolated from Xenopus laevis ovaries [Poll, E. H. A., & Benbow, R. M. (1988) Biochemistry 27, 8701-8706] was characterized biochemically. The directionality of DNA unwinding was determined to be 3' to 5'. A short 3' ssDNA tail adjacent to duplex DNA was required for DNA unwinding; the minimum length of this tail was between four and nine bases. Only short duplex DNA regions were unwound: duplex DNA of 16 base pairs was readily unwound, whereas a 26 base pair duplex was not. Longer duplex regions were unwound in the presence of Escherichia coli single-strand DNA binding protein if, in addition, the duplex region was flanked by an unpaired 3' or 5' tail and the substrate resembled a branched replicative intermediate. X. laevis DNA helicase I exhibited high affinity for ssDNA, moderate affinity for dsDNA, and no affinity for RNA. DNA unwinding activity was stimulated by monovalent cations, with an optimal concentration of 150 mM for NaCl or KCl or 125 mM for Na chi PO4 or K chi PO4. The ATP analog ATP gamma S inhibited the DNA unwinding and copurifying DNA-dependent ATPase activity, whereas AMPPCP and AMPPNP moderately inhibited DNA unwinding activity and had little effect on the copurifying DNA-dependent ATPase activity. CTP was a relatively strong inhibitor of DNA unwinding activity, but GTP, UTP, dCTP, dGTP, or TTP showed moderate or no inhibition. The copurifying DNA-dependent ATPase activity was not inhibited by CTP, GTP, UTP, dCTP, dGTP, or TTP.

Adenosine Triphosphatases↗