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Biomedical subjects

D A Walsh

Publications and source records attributed to D A Walsh.

At least 19 recordsLinked to original sources
PubMed2005

The genome of Salinibacter ruber: convergence and gene exchange among hyperhalophilic bacteria and archaea.

Saturated thalassic brines are among the most physically demanding habitats on Earth: few microbes survive in them. Salinibacter ruber is among these organisms and has been found repeatedly in significant numbers in climax saltern crystallizer communities. The phenotype of this bacterium is remarkably similar to that of the hyperhalophilic Archaea (Haloarchaea). The genome sequence suggests that this resemblance has arisen through convergence at the physiological level (different genes producing similar overall phenotype) and the molecular level (independent mutations yielding similar sequences or structures). Several genes and gene clusters also derive by lateral transfer from (or may have been laterally transferred to) haloarchaea. S. ruber encodes four rhodopsins. One resembles bacterial proteorhodopsins and three are of the haloarchaeal type, previously uncharacterized in a bacterial genome. The impact of these modular adaptive elements on the cell biology and ecology of S. ruber is substantial, affecting salt adaptation, bioenergetics, and photobiology.

Adaptation, Physiological↗
PubMed2004

Osteoarthritis, angiogenesis and inflammation.

Angiogenesis and inflammation are closely integrated processes in osteoarthritis (OA) and may affect disease progression and pain. Inflammation can stimulate angiogenesis, and angiogenesis can facilitate inflammation. Angiogenesis can also promote chondrocyte hypertrophy and endochondral ossification, contributing to radiographic changes in the joint. Inflammation sensitizes nerves, leading to increased pain. Innervation can also accompany vascularization of the articular cartilage, where compressive forces and hypoxia may stimulate these new nerves, causing pain even after inflammation has subsided. Inhibition of inflammation and angiogenesis may provide effective therapeutics for the treatment of OA by improving symptoms and retarding joint damage. This review aims to summarize (i) the evidence that angiogenesis and inflammation play an important role in the pathophysiology of OA and (ii) possible directions for future research into therapeutics that could effectively treat this disease.

Chronic Disease↗
PubMed2003

Post-mortem collection of human joint tissues for research.

OBJECTIVE: A feasibility study aiming to obtain post-mortem knee joint tissues from 10 donors for research. METHODS: Next of kin were approached by bereavement officers then informed about the project by the study nurse. Written consent was sought to collect bone, cartilage and soft tissue from both knees, and to extract data from medical notes. RESULTS: During the 4-month study period 259 families attended the King's Mill Hospital Bereavement Centre, 36 of whom met with the study nurse, 10 of whom consented to joint tissue collecting. The process of seeking consent required approximately 1 h of direct contact. Participants often looked to this as an extension of the bereavement counselling process and many expressed gratitude that some good might be derived from the death. Reasons for non-recruitment included operational restraints and relatives' distress. Donors were more likely to be male (90%) than were non-donors (49%, Z = -2.6, P < 0.01). Coroner's post-mortem examinations took place on similar proportions of donors (20%) and non-donors (19%, Z = -0.06, P = 0.96). CONCLUSIONS: Post-mortem joint tissue collection for research remains feasible in the presence of a skilled, well co-ordinated, multidisciplinary team, even when post-mortem examination would not otherwise be required.

Aged↗
PubMed2003

Inflammation and angiogenesis in osteoarthritis.

OBJECTIVE: To quantify the relationship between inflammation and angiogenesis in synovial tissue from patients with osteoarthritis (OA). METHODS: Hematoxylin and eosin staining and histologic grading for inflammation were performed for 104 patients who met the American College of Rheumatology criteria for OA and had undergone total joint replacement or arthroscopy. A purposive sample of synovial specimens obtained from 70 patients was used for further analysis. Vascular endothelium, endothelial cell (EC) proliferating nuclei, macrophages, and vascular endothelial growth factor (VEGF) were detected by immunohistochemical analysis. Angiogenesis (EC proliferation, EC fractional area), macrophage fractional area, and VEGF immunoreactivity were measured using computer-assisted image analysis. Double immunofluorescence histochemical analysis was used to determine the cellular localization of VEGF. Radiographic scores for joint space narrowing and osteophyte formation in the knee were also assessed. RESULTS: Synovial tissue samples from 32 (31%) of 104 patients with OA showed severe inflammation; thickened intimal lining and associated lymphoid aggregates were often observed. The EC fractional area, EC proliferation, and VEGF immunoreactivity all increased with increasing histologic inflammation grade and increasing macrophage fractional area. In the synovial intimal lining, VEGF immunoreactivity was localized to macrophages and increased with increasing EC fractional area and angiogenesis. No inflammation or angiogenic indices were significantly correlated with radiographic scores. CONCLUSION: Inflammation and angiogenesis in the synovium are associated with OA. The angiogenic growth factor VEGF generated by the inflamed synovium may promote angiogenesis, thereby contributing to inflammation in OA.

Aged↗
PubMed2002

Parents rate the ratings: a test of the validity of the American movie, television, and video game ratings.

BACKGROUND: Numerous studies have documented the potential effects on young audiences of violent content in media products, including movies, television programs, and computer and video games. Similar studies have evaluated the effects associated with sexual content and messages. Cumulatively, these effects represent a significant public health risk for increased aggressive and violent behavior, spread of sexually transmitted diseases, and pediatric pregnancy. In partial response to these risks and to public and legislative pressure, the movie, television, and gaming industries have implemented ratings systems intended to provide information about the content and appropriate audiences for different films, shows, and games. METHODS: We conducted a panel study to test the validity of the current movie, television, and video game rating systems. Participants used the KidScore media evaluation tool, which evaluates films, television shows, and video and computer games on 10 aspects, including the appropriateness of the media product for children on the basis of age. RESULTS: Results revealed that when an entertainment industry rates a product as inappropriate for children, parent raters agree that it is inappropriate for children. However, parent raters disagree with industry usage of many of the ratings designating material suitable for children of different ages. Products rated as appropriate for adolescents are of the greatest concern. The level of disagreement varies from industry to industry and even from rating to rating. CONCLUSIONS: Analysis indicates that the amount of violent content and portrayals of violence are the primary markers for disagreement between parent raters and industry ratings. Short-term and long-term recommendations are suggested.

Adult↗
PubMed2001

Angiogenesis in the pathogenesis of inflammatory joint and lung diseases.

This paper reviews hypotheses about roles of angiogenesis in the pathogenesis of inflammatory disease in two organs, the synovial joint and the lung. Neovascularisation is a fundamental process for growth and tissue repair after injury. Nevertheless, it may contribute to a variety of chronic inflammatory diseases, including rheumatoid arthritis, osteoarthritis, asthma, and pulmonary fibrosis. Inflammation can promote angiogenesis, and new vessels may enhance tissue inflammation. Angiogenesis in inflammatory disease may also contribute to tissue growth, disordered tissue perfusion, abnormal ossification, and enhanced responses to normal or pathological stimuli. Angiogenesis inhibitors may reduce inflammation and may also help to restore appropriate tissue structure and function.

Arthritis↗
PubMed2001

The cyclin-dependent kinase (CDK) inhibitor flavopiridol inhibits glycogen phosphorylase.

Flavopiridol has been shown to induce cell cycle arrest and apoptosis in various tumor cells in vitro and in vivo. Using immobilized flavopiridol, we identified glycogen phosphorylases (GP) from liver and brain as flavopiridol binding proteins from HeLa cell extract. Purified rabbit muscle GP also bound to the flavopiridol affinity column. GP is the rate-limiting enzyme in intracellular glycogen breakdown. Flavopiridol significantly inhibited the AMP-activated GP-b form of the purified rabbit muscle isoenzyme (IC50 of 1 microM at 0.8 mM AMP), but was less inhibitory to the active phosphorylated form of GP, GP-a (IC50 of 2.5 microM). The AMP-bound GP-a form was poorly inhibited by flavopiridol (40% at 10 microM). Increasing concentrations of the allosteric effector AMP resulted in a linear decrease in the GP-inhibitory activity of flavopiridol suggesting interference between flavopiridol and AMP. In contrast the GP inhibitor caffeine had no effect on the relative GP inhibition by flavopiridol, suggesting an additive effect of caffeine. Flavopiridol also inhibited the phosphorylase kinase-catalyzed phosphorylation of GP-b by inhibiting the kinase in vitro. Flavopiridol thus is able to interfere with both activating modifications of GP-b, AMP activation and phosphorylation. In A549 NSCLC cells flavopiridol treatment caused glycogen accumulation despite of an increase in GP activity, suggesting direct GP inhibition in vivo rather than inhibition of GP activation by phosphorylase kinase. These results suggest that the cyclin-dependent kinase inhibitor flavopiridol interferes with glycogen degradation, which may be responsible for flavopiridol's cytotoxicity and explain its resistance in some cell lines.

Adenosine Monophosphate↗
PubMed2001

Localization of 3-nitrotyrosine to rheumatoid and normal synovium.

OBJECTIVE: To determine the localization of 3-nitrotyrosine (3-NT), a footprint marker of peroxynitrite (ONOO-) and other reactive nitrogen species, to the inflamed human synovium and to compare this with normal synovial and nonsynovial tissue of human and animal origin. METHODS: Monoclonal and polyclonal antibodies were used to investigate for 3-NT, inducible nitric oxide synthase (iNOS), macrophage marker CD68, and the vascular smooth muscle marker alpha-actin by avidin-biotin immunocytochemistry. RESULTS: In the inflamed synovium, 3-NT was found in the vascular smooth muscle and macrophages. In normal human synovium, 3-NT was present in the vascular smooth muscle and some lining cells and was not associated with immunoreactivity for iNOS. Similarly, 3-NT could be demonstrated in the vascular smooth muscle cells of normal rats and iNOS knockout mice. It was not present in the vascular smooth muscle of healthy, nonsynovial tissue. CONCLUSION: The synovial vasculature in histologically normal human and naive rodent synovium was alone among the normal tissues studied in exhibiting iNOS-independent immunoreactivity for 3-NT. These findings suggest a physiologic role for ONOO- in normal synovial vascular function.

Actins↗
PubMed2001

Development of human fetal pancreas after transplantation into SCID mice.

Only a small component of human fetal pancreas consists of beta cells, and yet this tissue is capable of normalizing the blood glucose levels of diabetic recipients when transplanted. The time taken to achieve this goal is several months, during which time the tissue proliferates and eventually differentiates into beta cells. The dynamics of beta cell development have not been described previously. We transplanted human fetal pancreas beneath the renal capsule of immunodeficient mice and analysed the grafts for a period of 12 weeks using antibodies against exocrine cells (lipase), endocrine cells and protodifferentiated duct cells. Exocrine cells constituted 48% of all epithelial cells in the untransplanted pancreas, with duct cells comprising 29% and endocrine cells 16% (beta cells 7%). The percentage of exocrine cells declined with time after transplantation, with only a small number undergoing apoptosis, and the duct cells increased, the values for these two cell types at 12 weeks being 20 and 57%, respectively. Both cell types appeared to proliferate equally for up to 8 weeks after transplantation, but only duct cells thereafter. Endocrine cells began to increase from 8 weeks after transplantation, representing 28% of epithelial cells (beta cells 11%) at this time. Intermediate cells, that is, cells expressing the characteristics of more than one type of mature pancreatic cell, were observed both in the ungrafted pancreas and after transplantation. The commonest intermediate cell type was duct/exocrine, with exocrine/endocrine and duct/endocrine cells also observed, suggesting active transdifferentiation from one cell type to another. We hypothesize that following the transplantation of human fetal pancreatic tissue, exocrine cells mostly transdifferentiate into duct cells and these eventually develop into endocrine cells, in particular beta cells.

Animals↗
PubMed2001

Vasculature of the normal and arthritic synovial joint.

The vasculature of the normal and arthritic knee is described. The joint contains a number of different tissues, many of which are heterogeneous and each with varying degrees of vascularization. In the normal joint the vasculature is highly organised, some tissues are highly vascular with well defined vascular organisation, whilst other tissues are avascular. During arthritis vascular turnover is increased. This vascular plasticity leads to redistribution of the vascular bed and may compromise its functional ability. The normal joint is able to regulate its blood flow, but this ability may be compromised by the inflammation and increased synovial fluid volume that are associated with joint disease. Growth of the subchondral vasculature into the articular cartilage may also occur, leading to ossification of the articular cartilage.

Animals↗
PubMed2001

A validity test of movie, television, and video-game ratings.

CONTEXT: Numerous studies have documented the potential effects on young audiences of violent content in media products, including movies, television programs, and computer and video games. Similar studies have evaluated the effects associated with sexual content and messages. Cumulatively, these effects represent a significant public health risk for increased aggressive and violent behavior, spread of sexually transmitted diseases, and pediatric pregnancy. In partial response to these risks and to public and legislative pressure, the movie, television, and gaming industries have implemented ratings systems intended to provide information about the content and appropriate audiences for different films, shows, and games. OBJECTIVE: To test the validity of the current movie-, television-, and video game-rating systems. DESIGN: Panel study. MEASURE: Participants used the KidScore media evaluation tool, which evaluates films, television shows, and video games on 10 aspects, including the appropriateness of the media product for children based on age. RESULTS: When an entertainment industry rates a product as inappropriate for children, parent raters agree that it is inappropriate for children. However, parent raters disagree with industry usage of many of the ratings designating material suitable for children of different ages. Products rated as appropriate for adolescents are of the greatest concern. The level of disagreement varies from industry to industry and even from rating to rating. Analysis indicates that the amount of violent content and portrayals of violence are the primary markers for disagreement between parent raters and industry ratings. CONCLUSIONS: As 1 part of a solution to the complex public health problems posed by violent and sexually explicit media products, ratings can have value if used with caution. Parents and caregivers relying on the ratings systems to guide their children's use of media products should continue to monitor content independently. Industry ratings systems should be revised with input from the medical and scientific communities to improve their reliability and validity. A single ratings system, applied universally across industries, would greatly simplify the efforts of parents and caregivers to use the system as well as the efforts of outside parties to monitor the use and validity of the system.

Adolescent↗
PubMed2001

Nicotine dependence, depression, and the moderating role of goal cognitions.

The authors examined the moderating role of goal cognitions in the process of nicotine dependence in young adult smokers. A college sample of 85 male and 78 female smokers completed measures of nicotine dependence and psychological distress. They also provided cognitive evaluations for goals related to smoking cessation on scales measuring self-efficacy, value, planning, self-reward, self-criticism, self-monitoring, social comparison, and positive and negative goal-based arousal. As has been previously established, depression had a direct and significant effect on nicotine dependence. Moreover, significant interactions between goal cognitions and depression provided evidence for the hypothesized moderating effect.

Adolescent↗
PubMed2001

Angiogenesis: a therapeutic target in arthritis.

A variety of pharmacological strategies are being subjected to clinical trial to inhibit neovascularization of solid tumors. Increased angiogenesis is also a key component of synovitis and bone modeling in arthritis. Molecular mechanisms and pathological consequences of blood vessel growth in arthritis are now being elucidated. Preclinical studies of angiogenesis inhibitors in animal models of inflammatory arthritis support the hypothesis that inhibition of neovascularization may reduce inflammation and joint damage. Clinical data are consistent with these models being predictive of efficacy in rheumatoid arthritis. However, controlled studies of specific anti-angiogenic agents in human arthritis remain limited. Further studies are required to demonstrate that pharmacological agents can effectively inhibit articular angiogenesis, and ameliorate inflammation and subsequent joint damage. Potential toxicity of angiogenesis inhibitors in reproduction, growth and development and wound repair may be circumvented by short-term or local application, or by targeting molecular mechanisms that are specific to pathological rather than physiological angiogenesis.

Angiogenesis Inhibitors↗
PubMed2000

The challenge of the evolving media environment.

As media become more powerful and prominent, questions about their positive and negative effects on children and youth will increase. Although the body of quality research about media and youth is growing, there are some significant gaps. Three important areas for future research are identified: physiological research, differential effects research, and media education outcomes research.

Adolescent↗
PubMed2000

Angiotensin converting enzyme in human synovium: increased stromal [(125)I]351A binding in rheumatoid arthritis.

OBJECTIVE: To determine whether tissue angiotensin converting enzyme (ACE) is increased in synovia from patients with rheumatoid arthritis, osteoarthritis or chondromalacia patellae. METHODS: Sections of synovia from patients with rheumatoid arthritis (n = 7), osteoarthritis (n = 7) or chondromalacia patellae (n = 6) were tested for immunoreactivity for ACE, and for binding of the ACE inhibitor [(125)I]351A. The amount of ACE was measured with computer assisted image analysis as the proportion of synovial section area occupied by ACE-immunoreactive cells, and the density of [(125)I]351A binding. RESULTS: [(125)I]351A binding sites had characteristics of ACE and colocalised with ACE-like immunoreactivity to microvascular endothelium and fibroblast-like stromal cells in inflamed and non-inflamed human synovium. Stromal [(125)I]351A binding densities (B(eq)) and the fraction of synovial section area occupied by ACE-immunoreactivity (fractional area) were higher in synovia from patients with rheumatoid arthritis (B(eq) 28 amol/mm(2), fractional area 0.21) than from those with osteoarthritis (B(eq) 9 amol/mm(2), fractional area 0.10) or chondromalacia patellae (B(eq) 9 amol/mm(2), fractional area 0.09)(p < 0.05). Density of [(125)I]351A binding to stroma was similar to that to blood vessels in rheumatoid arthritis, but less dense than vascular binding in chondromalacia patellae and osteoarthritis. Increases in [(125)I]351A binding densities were attributable to increases in the numbers of binding sites, and were consistent with an increase in the density of ACE bearing stromal cells. CONCLUSION: ACE is upregulated in synovial stroma in rheumatoid arthritis. Increased tissue ACE may result in increased local generation of the vasoconstrictor and mitogenic peptide angiotensin II and thereby potentiate synovial hypoxia and proliferation in rheumatoid arthritis.

Adult↗
PubMed1999

Phosphorylase kinase: the complexity of its regulation is reflected in the complexity of its structure.

Intracellular glycogen stores are used to maintain blood-glucose homeostasis during fasting, are a source of energy for muscle contraction, and are used to support a broad range of cellular activities in most tissues. A diversity of signals accelerate glycogen degradation that are mediated by phosphorylase b kinase (Phk), which phosphorylates and thereby activates glycogen phosphorylase. Phk is among the most complex of the protein kinases so far elucidated. It has one catalytic (gamma) subunit and three different regulatory (alpha, beta, and delta) subunits, a molecular mass of 1.3 X 106 daltons, and each holoenzyme molecule is presumed to contain four molecules of each subunit. The three regulatory subunits inhibit the phosphotransferase activity of the gamma subunit. Ca2+ relieves inhibition via the delta subunit, which is identical to calmodulin but remains an integral component of the holoenzyme even when the [Ca2+] is lowered to nanomolar levels. Phosphorylation of the alpha and beta subunits by the 3',5'-cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) also relieves inhibition of the gamma subunit and thereby activates the enzyme. The stimulatory effects of Ca2+ and phosphorylation appear to be structurally coupled and are cooperative. In addition, Phk is activated in vitro by autophosphorylation, limited proteolysis of the regulatory subunits, and various allosteric effectors and these may also be mechanisms of physiological importance. The molecular mechanisms of regulation are currently poorly understood, but new insights are beginning to emerge. This review discusses current knowledge and concepts of the structure, function and regulation of Phk.

Amino Acid Sequence↗