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Biomedical subjects

Mark Harris

Publications and source records attributed to Mark Harris.

At least 37 records · Page 2Linked to original sources
PubMed2004

Hepatitis C virus NS5A: tales of a promiscuous protein.

The non-structural 5A (NS5A) protein of hepatitis C virus (HCV) has been the subject of intensive research over the last decade. It is generally accepted that NS5A is a pleiotropic protein with key roles in both viral RNA replication and modulation of the physiology of the host cell. Our understanding of the role of NS5A in the virus life cycle has been hampered by the lack of a robust in vitro system for the study of HCV replication, although the recent development of the subgenomic replicon has at least allowed us to begin to dissect the involvement of NS5A in the process of viral RNA replication. Early studies into the effects of NS5A on cell physiology relied on expression of NS5A either alone or in the context of other non-structural proteins; the advent of the replicon system has allowed the extrapolation of these studies to a more physiologically relevant cellular context. Despite recent progress, this field is controversial, and there is much work to be accomplished before we fully understand the many functions of this protein. In this article, the current state of our knowledge of NS5A, discussing in detail its direct involvement in virus replication, together with its role in modulating the cellular environment to favour virus replication and persistence, are reviewed. The effects of NS5A on interferon signalling, and the regulation of cell growth and apoptosis are highlighted, demonstrating that this protein is indeed of critical importance for HCV and is worthy of further investigation.

Amino Acid Sequence↗
PubMed2004

Growth hormone treatment in children: review of safety and efficacy.

Since the advent of growth hormone (GH), the pediatric applications of GH therapy have expanded. Children with a wide variety of growth disorders have received GH treatment. The therapeutic effects and safety profile of GH in a number of pediatric conditions are reviewed, including GH deficiency (GHD), Turner syndrome, chronic renal failure, children born small for gestational age, Prader-Willi syndrome, juvenile chronic arthritis, and cystic fibrosis. GH therapy has been clearly shown to improve height velocity during childhood in a variety of pediatric conditions in which growth is compromised. There is now data that confirms GH treatment also improves final height in a number of diagnostic subgroups. Early initiation and individualization of GH treatment has the potential to normalize childhood growth in children with idiopathic GHD and enable them to achieve their genetic target height in a cost-effective manner. In children in whom GHD is not the main factor compromising growth, supra-physiological doses of GH have been shown to increase height velocity during childhood and final height. The development of predictive models for these conditions may allow further improvements in height outcome while maintaining an acceptable safety profile. Survivors of childhood malignancy, particularly those who have had craniospinal irradiation, represent a particularly challenging group. They appear to be less responsive to GH than children with idiopathic GHD and have a tendency to enter puberty at an earlier age. Both of these factors have a negative impact on their final height. Strategies that combine GH treatment with suppression of puberty using a gonadotropin releasing hormone analog may result in improved height outcomes. When children with GHD are treated with standard doses of GH there is a strong safety record. Adverse events during GH therapy are uncommon and often not drug related. Continued surveillance into adult life is crucial however, particularly in children receiving supra-physiological doses of GH or whose underlying condition increases their risk of adverse effects.

Child↗
PubMed2004

Insulin sensitivity in the offspring of women with type 1 and type 2 diabetes.

OBJECTIVE: To determine if insulin sensitivity is altered in prepubertal offspring exposed to a diabetic intrauterine environment. RESEARCH DESIGN AND METHODS: Fifteen control children, 17 offspring of type 1 diabetic women, and 10 offspring of type 2 diabetic women, aged between 5 and 10 years, underwent a frequently sampled intravenous glucose tolerance test (FSIGTT). Weight and height were measured, and body composition was calculated using bioelectrical impedance. Bergman's minimal model was applied to the glucose and insulin measurements to obtain values for insulin sensitivity (Si), acute insulin response (AIR), and glucose effectiveness (Sg). RESULTS: Si was lowest in the offspring of type 2 diabetic mothers, and AIR was highest in this group, although neither of these changes reached significance (Si, P = 0.2, and AIR, P = 0.3). Offspring of type 2 diabetic mothers had higher BMI SD scores (P = 0.004) and percentage fat mass (P = 0.002) than the children in the other two groups. The BMI SD score and percentage fat mass in the subjects, as well as maternal insulin dose, were negatively correlated with offspring insulin sensitivity. CONCLUSIONS: Intrauterine exposure to hyperglycemia by itself was not associated with alterations in glucose regulation in prepubertal offspring. Children of mothers with type 2 diabetes, however, were overweight, and they had a tendency for a reduced Si. The combined effect of genetic and postnatal environmental factors, rather than prenatal exposure to hyperglycemia, may place this group at risk for developing impaired glucose tolerance in later life.

Adipose Tissue↗
PubMed2004

A smoking related triad: PAD, COPD and CCF.

BACKGROUND: Tobacco smoking is the modifiable risk factor responsible for the greatest burden of disease (loss of health and premature mortality) in Australia. OBJECTIVE: This article discusses the complexities of management of a patient suffering from a smoking related triad of illnesses: peripheral arterial disease, chronic obstructive pulmonary disease and ischaemic heart disease related congestive cardiac failure. DISCUSSION: As well as considering optimal management of the individual conditions, the patient's mental health and overall quality of life needs to be considered. Even at this late stage, smoking cessation is critically important. The patient is likely to require 6-8 medications, creating the potential for interactions and confusion, so careful medication management and patient education is required. The support of a multidisciplinary team will be required, with coordination of care being the key. Care planning and case conferencing between the general practitioner, the patient and other health professionals is essential for optimal care.

Behavior Therapy↗
PubMed2004

GP claims for completing diabetes 'cycle of care'.

BACKGROUND: There is a wide variability in the level of claims for diabetes. Service Incentive Payments (SIP) by general practitioners. METHOD: Cross sectional comparison of the ratio of the number of SIP items claimed between August 2002 and July 2003 to the estimated prevalence of diabetes by divisions of general practice (DGP). PARTICIPANTS AND SETTING: Seventy-nine of the 101 DGP with diabetes programs in 2002. RESULTS: The average ratio of diabetes SIP claims to estimated diabetes prevalence (including both diagnosed and undiagnosed cases) for each quarter of the year between August 2002 and July 2003 was 10.1% (standard deviation 3.6). This ratio was higher in DGP with a more disadvantaged population, and more of their GP members in large practices. The provision of IT support in DGP and the proportion of GPs who had patients registered on the division's register were associated with a higher ratio of claims. A multiple regression model with two factors: socioeconomic disadvantage and the proportion of GP members in practices of five or more GPs predicted 41% of the variance. CONCLUSION: Divisions of general practice appear to be supporting practices serving disadvantaged populations to deliver quality care for patients with chronic disease. The association with practice size and DGP activities suggests that practice organisation and systems are important in the provision of good care for patients with chronic disease.

Australia↗
PubMed2003

SNP cherry picker: maximizing the chance of finding an association with a disease SNP.

UNLABELLED: The high cost of genotyping single nucleotide polymorphisms (SNPs) generally prohibits the systematic mapping of entire genetic linkage regions in order to find the polymorphisms associated with increased risk of disease. In practice, SNPs are selected at approximately equal spacing across the linkage region to try to locate a SNP lying in the haplotype block of the disease SNP. The size of the haplotype block may not be known, however, and SNPs taken from public domain sources may not in fact be polymorphic. Our program will choose a subset of the SNPs in a linkage region so as to maximize the expected proportion of the sequence that lies within a given distance of a real SNP. AVAILABILITY: The software is available, free of charge, for academic use on request from the authors. SUPPLEMENTARY INFORMATION: www.oxagen.co.uk

Algorithms↗
PubMed2003

Engineering the exo-loop of Trichoderma reesei cellobiohydrolase, Cel7A. A comparison with Phanerochaete chrysosporium Cel7D.

The exo-loop of Trichoderma reesei cellobiohydrolase Cel7A forms the roof of the active site tunnel at the catalytic centre. Mutants were designed to study the role of this loop in crystalline cellulose degradation. A hydrogen bond to substrate made by a tyrosine at the tip of the loop was removed by the Y247F mutation. The mobility of the loop was reduced by introducing a new disulphide bridge in the mutant D241C/D249C. The tip of the loop was deleted in mutant Delta(G245-Y252). No major structural disturbances were observed in the mutant enzymes, nor was the thermostability of the enzyme affected by the mutations. The Y247F mutation caused a slight k(cat) reduction on 4-nitrophenyl lactoside, but only a small effect on cellulose hydrolysis. Deletion of the tip of the loop increased both k(cat) and K(M) and gave reduced product inhibition. Increased activity was observed on amorphous cellulose, while only half the original activity remained on crystalline cellulose. Stabilisation of the exo-loop by the disulphide bridge enhanced the activity on both amorphous and crystalline cellulose. The ratio Glc(2)/(Glc(3)+Glc(1)) released from cellulose, which is indicative of processive action, was highest with Tr Cel7A wild-type enzyme and smallest with the deletion mutant on both substrates. Based on these data it seems that the exo-loop of Tr Cel7A has evolved to facilitate processive crystalline cellulose degradation, which does not require significant conformational changes of this loop.

Amino Acid Sequence↗
PubMed2003

The hepatitis C virus non-structural NS5A protein inhibits activating protein-1 function by perturbing ras-ERK pathway signaling.

The hepatitis C virus nonstructural 5A (NS5A) protein is a pleiotropic phosphoprotein that has been shown to associate with a wide variety of cellular signaling proteins. Of particular interest is the observation that a highly conserved C-terminal Class II polyproline motif within NS5A mediated association with the Src homology 3 domains of members of the Src family of tyrosine kinases and the mitogenic adaptor protein Grb2 (A. Macdonald, K. Crowder, A. Street, C. McCormick, and M. Harris, submitted for publication). In this study, we analyzed the consequences of NS5A expression on mitogenic signaling pathways within a variety of cell lines. Utilizing a transient luciferase reporter system, we observed that NS5A inhibited the activity of the mitogenic and stress-activated transcription factor activating protein-1 (AP1). This inhibition was dependent upon a Class II polyproline motif within NS5A. Using a combination of dominant active and negative mutants of components of the MAPK signaling pathways, selective inhibitors, together with immunoblotting with phospho-specific and phosphorylation-independent antibodies, we determined the signaling pathways targeted by NS5A to inhibit AP1. These studies demonstrated that in both stable NS5A-expressing cells and Huh-7-derived cells harboring subgenomic hepatitis C virus (HCV) replicons, this inhibition was mediated through the ERK signaling pathway. Importantly, a comparable inhibition of AP1 reporter activity was observed in hepatocyte-derived cell lines transduced with a baculovirus vector driving expression of full-length HCV polyprotein. In conclusion, these data strongly suggest a role for the NS5A protein in the perturbation of mitogenic signaling pathways in HCV-infected hepatocytes.

Amino Acid Motifs↗
PubMed2003

Iodine deficiency and goitre in schoolchildren in Melbourne, 2001.

OBJECTIVE: To assess iodine status and goitre prevalence in a sample of schoolchildren in Melbourne. DESIGN: Cross-sectional study of urinary iodine excretion and presence of goitre in a sample of schoolchildren from Years 5-12 attending two urban schools. PARTICIPANTS: 607 children aged 11-18 years consented to thyroid gland palpation and 577 provided a urine sample on the day of examination in August 2001. OUTCOME MEASURE: Iodine status of the study population, based on median urinary iodine values categorised as normal (> or = 100 microg/L), mild (50-99 microg/L) or moderate-severe (< 50 microg/L), and classified according to sex, school year and presence of goitre. RESULTS: 76% (439/577) of students had abnormal urinary iodine values, with 27% (156/577) having values consistent with moderate-severe deficiency. The median urinary iodine excretion for the total group was 70 microg/L, with values for school years 5-12 ranging from 62 microg/L (Year 12) to 76 microg/L (Year 9). The median urinary iodine value in girls was lower than that in boys (64 microg/L v 82 microg/L), and girls had significantly lower urinary iodine values overall (P < 0.002). There was no association between goitre grade and moderate-severe (< 50 microg/L; P = 0.39) or mild (50-99 microg/L; P = 0.07) urinary iodine deficiency. CONCLUSIONS: We found mild iodine deficiency in a cohort of schoolchildren in Melbourne. Our results support other data showing mild iodine deficiency in Sydney and Tasmania and the argument for a national study of iodine nutrition.

Adolescent↗
PubMed2003

HIV-1 Nef induces the release of inflammatory factors from human monocyte/macrophages: involvement of Nef endocytotic signals and NF-kappa B activation.

It has been recently reported that the endogenous expression of HIV-1 Nef in human monocyte/macrophages induces the release of chemokines and other as yet unidentified soluble factors leading to multiple effects of pathogenic significance, such as the recruitment and activation of quiescent lymphocytes. However, the description of underlying molecular mechanisms remained elusive. We recently demonstrated that human monocyte-derived macrophages (MDM) efficiently internalize soluble rNef, thereby inducing effects largely resembling those observed in cells endogenously expressing Nef. By exploiting the rNef/MDM model, we sought to gain more insights on the molecular mechanisms underlying the response of MDM to Nef. Array analysis for the detection of transcripts from a large number of monokines, chemokines, cytokines, and receptors thereof showed that MDM promptly responded to rNef treatment by increasing the transcription of genes for several inflammatory factors. Analysis of supernatants revealed that rNef treatment induced the release of macrophage inflammatory proteins 1alpha and 1beta, IL-1beta, IL-6, and TNF-alpha. Conversely, rNefs mutated in domains critical for the interaction with the endocytotic machinery (i.e., EE155-156QQ, and DD174-175AA) were ineffective. Interestingly, we found that the Nef-dependent release of inflammatory factors correlated with the activation of the NF-kappaB transcription factor, mainly in its p50/p50 homodimeric form, and in a de novo protein synthesis-independent manner. Our data add new hints supporting the idea that the presence of Nef is per se heavily detrimental for monocyte/macrophages and relative cross-talking cell types.

Adult↗
PubMed2003

The di-leucine motif in the cytoplasmic tail of CD4 is not required for binding to human immunodeficiency virus type 1 Nef, but is critical for CD4 down-modulation.

The human immunodeficiency virus type 1 (HIV-1) nef gene encodes a 205 residue, myristoylated phosphoprotein that has been shown to play a critical role in the replication and pathogenesis of the virus. One of the most studied functions of the Nef protein is the down-modulation of cell surface CD4. Nef has been reported to interact with both the cytoplasmic tail of CD4 and proteins that are components of the endocytic machinery, thereby enhancing the endocytosis of CD4 through clathrin-coated pits. A di-leucine motif in the cytoplasmic tail of CD4 (residues 413/414) was reported to be essential both for Nef mediated down-modulation and for Nef binding. In order to further characterize the involvement of this di-leucine motif in CD4 down-modulation we generated a CD4 mutant in which the leucines were substituted by alanines, termed CD4(LL-AA). We demonstrate here that, contrary to previous data obtained with the cytoplasmic tail of CD4 alone, full-length CD4(LL-AA) bound to Nef both in vivo, in recombinant baculovirus-infected Sf9 cells, and in vitro. In contrast the di-leucine motif was required for both Nef-mediated and phorbol ester-induced CD4 down-modulation, suggesting that the essential requirement for the di-leucine motif in CD4 down-modulation reflects the fact that this motif is needed for the interactions of CD4 with the endocytic machinery, not for the interaction with Nef. We have also exploited the observation that CD4(LL-AA) is refractory to Nef-mediated down-modulation to provide the first experimental evidence for a physical interaction between Nef and CD4 in intact mammalian cells.

Amino Acid Motifs↗
PubMed2003

Reversible metaphyseal dysplasia, a novel bone phenotype, in two unrelated children with autoimmunepolyendocrinopathy-candidiasis-ectodermal dystrophy: clinical and molecular studies.

We report the association of an undescribed, reversible metaphyseal dysplasia (RMD) with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) in two patients, one homozygous and one heterozygous for a 13-bp deletion in exon 8 of the autoimmune regulator (AIRE) gene. One patient also had a novel deletion in exon 6, resulting in a frameshift mutation and introduction of a STOP codon in exon 10. Their APECED phenotypes differed, but both patients developed progressive skeletal deformities and growth failure from early childhood. Radiological examination suggested a generalized abnormality of endochondral ossification, with irregular, flared, radioopaque regions in the metaphyses, subjacent to the growth plates. Histopathology in patient 1 showed islands of calcified cartilage within bone, consistent with impaired coupling of cartilage resorption with vascular invasion and ossification. Despite discordance for puberty, both patients experienced radiological resolution of their bone disease in their mid-teens, with improvement in histopathology in patient 1. RMD may constitute a rare phenotypic variation of APECED, possibly resulting from autoimmunity directed against skeletal proteins. We also demonstrated AIRE expression in chondrocytes derived from human fetal growth plates, primary culture of human chondrocytes, and two chondrosarcoma cell lines, suggesting a potential role for abnormal AIRE expression in the development of RMD.

Adult↗
PubMed2003

Prostate cancer.

Explore the source record for details and available documents.

Aged↗
PubMed2002

Randomised controlled trial of home based care of patients with chronic obstructive pulmonary disease.

OBJECTIVES: To evaluate usefulness of limited community based care for patients with chronic obstructive pulmonary disease after discharge from hospital. DESIGN: Randomised controlled trial. SETTING: Liverpool Health Service and Macarthur Health Service in outer metropolitan Sydney between September 1999 and July 2000. PARTICIPANTS: 177 patients randomised into an intervention group (84 patients) and a control group (93 patients) which received current usual care. INTERVENTIONS: Home visits by community nurse at one and four weeks after discharge and preventive general practitioner care. MAIN OUTCOME MEASURES: Frequency of patients' presentation and admission to hospital; changes in patients' disease-specific quality of life, measured with St George's respiratory questionnaire, over three months after discharge; patients' knowledge of illness, self management, and satisfaction with care at discharge and three months later; frequency of general practitioner and nurse visits and their satisfaction with care. RESULTS: Intervention and control groups showed no differences in presentation or admission to hospital or in overall functional status. However, the intervention group improved their activity scores and the control group worsened their symptom scores. While intervention group patients received more visits from community nurses and were more satisfied with their care, involvement of general practitioners was much less (with only 31% (22) remembering receiving a care plan). Patients in the intervention group had higher knowledge scores and were more satisfied. There were no differences in general practitioner visits or management. CONCLUSIONS: This brief intervention after acute care improved patients' knowledge and some aspects of quality of life. However, it failed to prevent presentation and readmission to hospital.

Adult↗
PubMed2002

Xtrack - a web-based crystallographic notebook.

Xtrack is a web-based database-backed crystallographic notebook system that allows groups of workers to keep track of crystallographic project data from the crystallization stage through to data bank deposition. A working demonstration version is available from http://xray.bmc.uu.se/xtrack and the code is available for those who wish to set up their own databases.

Crystallography, X-Ray↗
PubMed2002

Age-related differences in vision and proprioception in a lower limb interceptive task: the effects of skill level and practice.

This study examined age-related differences in the role of visual proprioception during a lower limb interceptive action and how this varies as a function of skill and practice. In Experiment 1, skilled and less-skilled 8-, 10-, and 12-year-old boys controlled a soccer ball using their preferred foot under full vision and when sight of the effector was occluded. With the exception of the high-skilled 12-year-olds and low-skilled 8-year-olds, participants showed a decrement in peformance when denied access to visual proprioception. In Experiment 2, the effect of practicing under different informational constraints was examined for 12 year-old boys. Children performed varying amounts of practice under full vision, or in a condition where sight of the foot was occluded, before being transferred to the alternative viewing condition. Participants who practiced under occluded viewing conditions showed greater relative improvement in performance over practice and transfer sessions compared with a full vision control group. Some support is provided for the manipulation of visual informational constraints as an effective pedagogical approach to motor learning.

Age Factors↗