Preventing sports and leisure injuries.
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Athletic Injuries↗
Biomedical subjects
D Stone
Publications and source records attributed to D Stone.
Breastfeeding, dummy use, and adult intelligence.
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Aged↗
Role of lipid hydroperoxides in the activation of 15-lipoxygenase.
We have used stopped-flow rapid reaction methods, employing both fluorescence and absorbance monitoring, together with HPLC analysis of the products to study the activation of soybean 15-lipoxygenase by 13(S)-hydroperoxy-9, 11(E,Z)-octadecadienoic acid (13-HPOD). When lipoxygenase is mixed with an equimolar concentration of 13-HPOD, the enzyme undergoes a rapid change in fluorescence. The rate of the change of fluorescence is dependent on the concentration of the 13-HPOD (k = 6.7 x 10(6) M-1 s-1) and is accompanied by activation of the enzyme. The fluorescence change is not accompanied by any change in the UV absorbance of the 13-HPOD, suggesting no loss of the conjugated diene during enzyme activation, and HPLC analysis of the products of the reaction confirms that the 13-HPOD can be recovered unchanged following this reaction. In the presence of an inhibitor (BWA4C, a hydroxamate inhibitor) that reduces the active-site iron, the 13-HPOD and the inhibitor are destroyed in a peroxidase-like reaction. On the basis of these observations we propose that 13-HPOD binds to the enzyme and facilitates activation of the enzyme, possibly through the formation of a protein radical, and that the 13-HPOD is not changed chemically in this process.
Arachidonate 15-Lipoxygenase↗
The resistance of low density lipoprotein to oxidation promoted by copper and its use as an index of antioxidant therapy.
The measurement ex vivo of the resistance of low density lipoprotein (LDL) to oxidation promoted by copper is now being used in surveys of human populations at risk of developing atherosclerosis. However, it is not known whether a relationship between LDL oxidisability measured in this way and the development of atherosclerotic lesions exists. Using Watanabe rabbits as a model of the disease, we have found that dietary supplementation with the antioxidants, probucol and alpha-tocopherol, increased the resistance of LDL isolated from small volumes of plasma to oxidation. The antioxidant effects of probucol incorporated into LDL through dietary supplementation were greater than when incorporated ex vivo. When dietary supplementation was extended to a period of three months, the well established anti-atherosclerotic effects of probucol were confirmed and a highly significant relationship between the probucol content of the LDL particle and the extent of the atherosclerotic lesion in the aorta emerged. These results suggest that the assessment of the resistance of LDL isolated from plasma to oxidation promoted by copper may reflect the response of the arterial atherosclerotic process to antioxidant therapy.
Administration, Oral↗
Full-length agrin isoform activities and binding site distributions on cultured Xenopus muscle cells.
Agrin is a large multidomain protein involved in the induction of postsynaptic differentiation of the neuromuscular junction. As a step toward further understanding the mechanisms by which agrin induces the aggregation of acetylcholine receptors (AChRs), we have characterized the activity of purified, full-length chick agrin isoforms on Xenopus muscle cells. Incubation with agrin isoforms led to the formation of numerous small AChR clusters primarily on the ventral surface of cells with differing efficacies: Y4Z8 > Y4Z11 = Y4Z19, with Y4B0 being ineffective. Agrin activity appeared to be tyrosine phosphorylation-dependent as the kinase inhibitor tyrphostin RG50864 (80 microM) completely abolished the effect. Initial binding sites for all agrin isoforms were evenly distributed in a punctate manner on the muscle cell surface. After a 14-h incubation, the active isoforms induced AChR clustering, and agrin was enriched at these sites of clustering. Agrin binding to the cell surface and induction of AChR clustering were Ca(2+)-dependent, as previously shown in other systems. This is the first quantitative characterization of agrin's effects using Xenopus cell culture, providing a basis for further elucidating agrin's role in synaptogenesis using this elegant system.
Agrin↗
The role of an agrin-growth factor interaction in ACh receptor clustering.
The clustering of acetylcholine receptors (AChRs) at the neuromuscular junction is mediated in part by the heparan-sulfate proteoglycan agrin. However, our previous studies have also suggested the role of heparin-binding growth-associated molecular (HB-GAM) in AChR clustering. Here the role of an agrin-HB-GAM interaction in this process was examined using cultured Xenopus muscle cells. Agrin-coated beads further treated with HB-GAM were highly effective in AChR cluster induction. Protein overlay assays showed specific binding of HB-GAM to agrin. In addition, agrin-enriched neuritic tracks bound HB-GAM in a manner that showed a high degree of colocalization between the neural agrin and the applied factor. Finally, the introduction of exogenous HB-GAM together with soluble agrin resulted in the appearance of AChR clusters on the dorsal surface of cells in an agrin isoform-dependent manner; a dramatic change from the characteristic ventral AChR clustering seen in response to agrin alone. These results suggest that agrin may mediate AChR clustering by interacting with muscle-bound heparin-binding growth factors such as HB-GAM.
Agrin↗
Characterization of familial partial 10p trisomy by chromosomal microdissection, FISH, and microsatellite dosage analysis.
Unbalanced translocations are a frequent cause of multiple congenital anomalies in children. Translocations as small as 2-5 Mb of DNA are detectable by G-banding under optimal conditions. Some of these small translocations are visible but cannot be characterized cytogenetically due to the lack of characteristic banding on Giemsa preparations. We have combined chromosomal microdissection and fluorescence in situ hybridization (FISH) to identify the origin of a small translocated segment in three members of a family with a derivative chromosome 9 and multiple anomalies, including several ophthalmologic anomalies. We microdissected the abnormal region of the derivative 9 chromosome and used this DNA to generate a FISH probe. This probe hybridized to distal 10p on the metaphase spread of the proband, indicating the origin of the translocated segment. A whole 10p FISH probe confirmed the origin by hybridizing to the translocated segment of the derivative chromosome. FISH was then performed with a whole chromosome 9 painting probe and excluded the presence of a reciprocal, balancing translocation. We then studied the chromosome 10 partial duplication with microsatellite markers to better characterize the chromosomal segment that caused these phenotypic features. By examining the involved areas with distal 10p and 9p microsatellite markers, we were able to demonstrate a minimum of 9 Mb of trisomic 10p DNA with a chromosomal breakpoint between 10p14-10p15. We then compared this family's clinical findings to those of individuals with partial 10p trisomy who had been reported in the literature. The clinical phenotypes seen in this family are similar to, but milder than, the phenotypes of persons with the larger partial trisomies of 10p that were diagnosable by cytogenetic analysis alone. This study shows that microdissection and DNA markers can be used to precisely define small translocations that are difficult to identify by conventional G-banded chromosome analysis.
Abnormalities, Multiple↗
Oxidation of human low-density lipoprotein by soybean 15-lipoxygenase in combination with copper (II) or met-myoglobin.
The enzyme 15-lipoxygenase has been implicated in the oxidation of low-density lipoprotein (LDL) in human atherosclerotic lesions. The biochemical mechanism for this oxidative process is not fully understood, and the interaction of the lipoxygenase-modified lipoprotein with metals or metalloproteins has not been explored. In the present study we have used soybean lipoxygenase to model the interaction of the enzyme with LDL and show that a direct oxygenation of fatty acids occurs, including those esterified to cholesterol, with no lag phase or change in electrophoretic mobility of the LDL particle but with some depletion of alpha-tocopherol. The enzyme-dependent oxidation may involve propagation through the release of peroxyl radicals from its active site but appears to have no requirement for free iron or copper. When lipoxygenase-treated LDL is exposed to either copper (II) or metMb, a rapid oxidation process occurs, resulting in a marked decrease in resistance to oxidation and an increase in the rate of modification to a form with increased electrophoretic mobility. This effect was not seen if lipoxygenase-treated LDL was oxidized by SIN-1, a peroxynitrite donor that oxidizes LDL with no requirement for endogenous lipid hydroperoxides. We propose that a synergistic interaction may occur between the peroxides inserted into LDL as a consequence of the enzymatic action of lipoxygenase with haem proteins or copper, which decreases the potency of the endogenous antioxidants and enhances oxidation.
Arachidonate 15-Lipoxygenase↗
Home alone: is it a risk factor for middle school youth and drug use?
This study examined the relationship between middle school/junior high student latchkey status and early experimentation and use of alcohol, tobacco, and other drugs. Students were queried about the frequency (number of times per week) and quantity (number of hours per day) of unsupervised after school days in an average week. Questions were also asked regarding their experiences with "gateway" drugs, inhalants, and steroids. Chi square analysis was used to test the strength of association. The results of this study indicated that latchkey youth (LKY) who were home alone two or more days per week were four times more likely to have gotten drunk in the past month than those youth who had parental supervision five or more times a week. Also, significant differences were observed for LKY with respect to cigarette smoking, inhalants, and marijuana use. Other findings and demographic variables were discussed as they pertain to LKY as well as suggested strategies for healthy self-care alternatives.
Adolescent↗
Stimulation of mitochondrial oxygen consumption in isolated cardiomyocytes after hypoxia-reoxygenation.
An increase in mitochondrial matrix free calcium has been shown to occur during oxygen and substrate deprivation of the perfused heart which predisposes to calcium overload and inhibition of mitochondrial function on reoxygenation. In the current study we have assessed the effect of substrate free hypoxia on mitochondrial oxygen consumption and ATP synthesis in isolated rat cardiomyocytes. Myocytes were subjected to 40 min of substrate-free hypoxia and the oxygen consumption measured together with the effects on ATP and PCr synthesis. After hypoxia myocytes showed a fall in ATP to 10% of the control value. Within 5 sec of reoxygenation the ATP level recovered to a new steady state level of 30% of the original value. The rate of oxygen consumption of hypoxic/reoxygenated cells was 3-4 fold higher than that of cells maintained under normoxic controls but in the presence of oligomycin the difference was only 1.5-fold higher, indicating a greater requirement for mitochondrial synthesis of ATP following reoxygenation. Reoxygenation in the absence of extracellular Ca2+ resulted in a lower rate of oxygen consumption (50% of the rate measured in the presence of 1 mM-Ca2+) but did not affect the steady state concentration of ATP attained 5 min after reoxygenation. These results support the idea that the increased O2 consumption of myocytes following hypoxia/reoxygenation is due to an increased demand for ATP synthesis by mitochondria and is a response to the NA+ and Ca2+ loading of the cells which occurs under these conditions. This increased demand is likely to result in a greater generation of free radicals such as superoxide by the respiratory chain which could impair cellular function over the long term.
Adenine Nucleotides↗
Human (THP-1) macrophages oxidize LDL by a thiol-dependent mechanism.
The oxidative modification of low-density lipoprotein by macrophages may be an important mechanism in the pathogenesis of atherosclerosis. The human monocytic leukaemic cell line THP-1, when stimulated with phorbol ester, shares many properties with human monocyte-derived macrophages. Oxidation of LDL by these cells was characterised by depletion of alpha-tocopherol, increases in thiobarbituric acid reactive substances and increases in electrophoretic mobility. The LDL particles were also converted to a form which increased accumulation of cholesteryl esters within macrophages. The oxidative mechanism appeared to be dependent upon the presence of thiols in the cellular medium. Oxidation of LDL by THP-1 macrophages, and production of thiols by these cells, were dependent upon the presence of L-cystine in the medium. Furthermore, cellular oxidation of LDL could be partially mimicked by the addition of cysteine to Hams F10 medium. Macrophage-independent oxidation of LDL, mediated by the addition of copper ions, was inhibited by cystine and cysteine in phosphate buffered saline, but not in Hams F10 medium. The glutathione content of THP-1 macrophages was also dependent upon the presence of cysteine or cystine in the medium, but inhibition of glutathione synthesis by buthionine sulfoximine did not prevent the production of thiols or the oxidation of LDL by THP-1 macrophages.
Buthionine Sulfoximine↗
Screening in Scotland.
A survey of screening in Scottish Health Boards suggests that, with the exceptions of screening in the antenatal period, for some conditions in the neonatal period and for the two national programmes for breast and cervix in adult women, practice is by no means uniform across all Boards and there is a lack of systematic evaluation. Four suggestions are made to improve equity, quality and relevance of screening: (i) national guidelines should be formulated to promote the implementation of the same core screening activities in all Boards; (ii) audit and quality control programmes should be universal and systematically applied; (iii) the demarcations of professional and managerial responsibilities and lines of accountability should be clarified; (iv) any proposed new screening programmes should be assessed in the light of the World Health Organisation principles before their introduction.
Adolescent↗
Expression of the pim-1 protooncogene: differential inducibility between alpha/beta- and gamma/delta-T cells and B cells.
The pim-1 gene encodes a serine/threonine protein kinase with expression restricted primarily to cells of hematopoietic lineage and is thought to play a role in the signal transduction events associated with lymphocyte activation. A rapid increase in pim-1 mRNA levels was found after stimulation of normal unseparated PBMCs with phorbol ester (PMA) and a calcium ionophore (ionomycin) with the peak level occurring 4 hr poststimulation. Treatment of PBMCs with ionomycin alone caused only a minimal increase in pim-1 mRNA, whereas treatment with PMA alone induced a large increase in pim-1 mRNA, suggesting that the activation of a signaling pathway involving protein kinase C is responsible for the accumulation of this transcript. In enriched subpopulations of resting alpha/beta-T cells, gamma/delta-T cells, and B cells, pim-1 expression was found to be constitutively expressed, albeit at lower levels in T cells. This basal level of pim-1 expression could be increased by stimulation of alpha/beta-T cells (approx fivefold) and gamma/delta-T cells (approximately sevenfold) with PMA plus ionomycin. In contrast, pim-1 expression was not inducible in B cells. In PBMCs, half-life determination studies showed that turnover of pim-1 mRNA was markedly prolonged as a result of message stabilization induced by PMA plus ionomycin treatment. In addition, stable pim-1 transcripts were also observed in all transformed lymphoid cell lines examined. Taken together, these results suggest that the stability of pim-1 transcripts may be linked to the regulation of cell growth and represent the first direct demonstration that pim-1 expression is indeed regulated in a cell-type-specific manner.
Animals↗
Alpha-tocopherol mediated peroxidation in the copper (II) and met myoglobin induced oxidation of human low density lipoprotein: the influence of lipid hydroperoxides.
The principal antioxidant in human LDL, alpha-tocopherol, is converted to the alpha-tocopheroxyl radical after reaction with peroxyl radicals or Cu2+, and, if it does not terminate with peroxyl radicals, could initiate lipid peroxidation; a phenomenon called 'tocopherol mediated peroxidation'. Only in the presence of Cu2+ and low levels of lipid hydroperoxides was an alpha-tocopherol dependent decrease in the resistance of LDL to oxidation detected. This suggests that tocopherol mediated peroxidation will probably not contribute significantly as a pro-oxidant process in those individuals most at risk of developing atherosclerosis through an oxidative mechanism.
Azoles↗
Drug firms need biotech drug discovery.
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Acquired Immunodeficiency Syndrome↗
HIV protease inhibitors head to market.
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Clinical Trials as Topic↗
Epidemiology of Down's syndrome in a Scottish city.
The aim of the study was to investigate aspects of the epidemiology of Down's syndrome (DS) in a population subjected to continuous surveillance. Data were obtained from the Glasgow Register of Congenital Anomalies. Over the period 1980-90, 173 cases of DS were identified (1.2 per 1000 births), of which 135 (78.1%) were livebirths, five (2.9%) were stillbirths and 33 (19.1%) were terminations following prenatal diagnosis. The increasing risk of DS with advancing maternal age was confirmed, although most DS pregnancies occurred in women aged under 35. While the birth prevalence of DS did not vary significantly over time, there was a significant increase in DS pregnancy prevalence. The proportion of all DS pregnancies terminated showed a statistically significant rise from 14% in 1980-87 to 31% in 1988-90 following the introduction of a new screening marker for DS risk. Almost half of DS pregnancies in women aged 35 and over ended in termination following prenatal diagnosis compared with only 7% in women under 35. There was a statistically significant excess risk of DS pregnancy in the more prosperous areas of the city; this excess persisted, but was not statistically significant, after standardising the rates for maternal age. These findings suggest that there is no scope for reducing service provision for DS children on the basis of the epidemiological trends, that the antenatal screening programme, while benefiting from the recent introduction of serum markers of risk, continues to have a greater impact on older women, and that further aetiological research using population based registries is required.
Abortion, Therapeutic↗