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Biomedical subjects

J Owens

Publications and source records attributed to J Owens.

At least 73 records · Page 4Linked to original sources
PubMed1996

Power in partnership.

This paper focuses on the meaning and process of collaboration, particularly in the area of research and clinical practice. Much has been written about the existing gaps between research and the practice of nursing; however, action research is one mechanism that allows these elements to be drawn together. Research developed through collaborative participation has the potential to harness the energy, enthusiasm and talents of nurses at different levels and practice into a cohesive group motivated to achieve professional development and quality practice goals. Action research that is built on the philosophy of a quality within the process and significance of the group can lead to effective practice in nursing. Power can be found in partnership.

Cooperative Behavior↗
PubMed1996

A 3-month home use study comparing the oral hygiene and gingival health benefits of triclosan and conventional fluoride toothpastes.

A number of triclosan toothpastes are available which have been shown to benefit gingival health when compared to triclosan free control formulations. There have been few studies to compare such active products with conventional fluoride toothpaste products. The aim of this study was to compare, in home use, a triclosan product with conventional fluoride products already found to show slightly less plaque inhibition in a short term plaque regrowth study. The study was a single-blind, parallel design with a total of 129 healthy dentate volunteers (32 male, 97 female) who toothbrushed with one of 4 toothpaste products at home, twice a day over a period of 12 weeks. At the beginning of the trial, each volunteer was scored for plaque and gingivitis and then received a through prophylaxis. Each volunteer was allocated a toothpaste according to a predetermined randomisation scheme. The volunteers were re-examined after 6 and 12 weeks. The volunteers refrained from using any other oral hygiene products during the period of the trial. The toothpastes tested were two conventional fluoride toothpastes, a children's fluoride toothpaste and a triclosan/copolymer toothpaste. Results indicated that there were no overall significant treatment differences for either plaque index or gingival index and ordering of toothpastes was not possible. All volunteers' oral hygiene and gingivitis improved following the 6-week period and continued to improve to the 12th week. This is a feature of most oral hygiene trials and presumably arises from the initial prophylaxis and a Hawthorne response of improved toothcleaning by the subjects. It must be concluded from this study that in normal home use the triclosan/copolymer toothpaste provides oral hygiene and gingival health benefits no greater than achievable with conventional toothpaste products.

Adolescent↗
PubMed1996

Long-term follow-up of rehabilitated patients with chronic psychiatric illness in Ireland.

In 1994 a 20-year retrospective study was conducted of 297 psychiatric patients admitted to an inpatient rehabilitation program in rural Ireland over a 15-year period (1974 to 1989). All patients were traced. Seventy-six percent had been discharged into the community, and two-thirds required supported housing. Fifty-five percent had experienced acute psychiatric readmissions, and 17 percent became new long-stay patients. The main criticisms of deinstitutionalization did not apply to these patients. No patient became homeless. One patient became involved in possible criminal activity. Four patients committed suicide, and the annual death rate was low-1.8 per 100 patients. The model of care involved was a key factor in the satisfactory outcome.

Adolescent↗
PubMed1995

Suppression of evoked IPSPs by arachidonic acid and prostaglandin F2 alpha.

Arachidonic acid (AA) and certain prostaglandins appear to antagonize GABAA receptors in synaptoneurosomes [18]. We report here that perfusing hippocampal slices with AA or prostaglandin F2 alpha diminishes evoked IPSP conductance and increases CA1 pyramidal cell input resistance. The effects of the two compounds were similar, though not identical, in time course, magnitude, and response to washout. These findings suggest that high levels of AA and its metabolites may bias neurons towards excitation.

Analysis of Variance↗
PubMed1995

The effect of hepatocyte growth factor on the behaviour of osteoclasts.

Hepatocyte growth factor (HGF) stimulates the growth, motility and morphogenesis of a variety of cell types, including hemopoietic progenitors. We found that HGF is a potent inhibitor of bone resorption by isolated rat osteoclasts. However, in the presence of the osteoblastic cell line UMR 106, it stimulated osteoclastic resorption. HGF also increased osteoclastic motility and spread area, over a similar concentration range. We detected no effect on osteoclast formation or survival. Our data suggest that HGF may be involved in the recruitment of osteoclasts to sites of bone resorption, but that during migration resorptive functions are suppressed. Once on resorptive sites, the osteoclast response to HGF is modulated by osteoblastic cells and the bone resorptive activity of osteoclasts may be stimulated accordingly.

Animals↗
PubMed1995

Iodine-mediated inactivation of lipid- and nonlipid-enveloped viruses in human antithrombin III concentrate.

Human plasma-derived protein concentrates intended for clinical use must be treated for viral inactivation to ensure patient safety. This study explored the use of liquid iodine for inactivation of several lipid- and nonlipid-enveloped viruses in an antithrombin III (AT-III) concentrate. Iodine at levels of 0.01% to 0.02% caused between 43% and 94% loss of AT-III activity, as well as degradation of AT-III as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis. However, addition of up to 0.1% human albumin protected the AT-III against both inactivation and fragmentation. At albumin levels sufficient to retain greater than 75% of AT-III activity, greater than 6 logs of sindbis, encephalomyocarditis, and vesicular stomatitis viruses, greater than 4 logs of pseudorabies, and greater than 3 logs of human immunodeficiency virus were inactivated. Except with sindbis virus, this represented complete inactivation of all the viruses spiked into the AT-III concentrate.

Animals↗
PubMed1995

Enhanced tumour uptake and in vitro radiotoxicity of no-carrier-added [131I]meta-iodobenzylguanidine: implications for the targeted radiotherapy of neuroblastoma.

In vitro and in vivo neuroblastoma models were used to determine whether improvements in tumour targeting in vivo and therapeutic efficacy in vitro could result from the use of no-carrier-added (n.c.a.) [131I]MIBG. Results were compared with use of the conventional therapy MIBG preparation (ex. [131I]MIBG) of lower specific activity which is produced by iodide exchange reaction. The efficacy of n.c.a. [131I]MIBG was compared with that of [131I]MIBG over a range of specific activities by the assessment of neuroblastoma spheroid growth delay. Whereas n.c.a. [131I]MIBG at a radioactivity concentration of 2 MBq/ml prevented the regrowth of 84% of spheroids, toxicity was significantly reduced by the addition of non-radiolabelled MIBG to the incubation medium. The time-dependent biodistribution of n.c.a. [131I]MIBG in nude mice bearing human neuroblastoma xenografts was compared with that of the conventional therapy radiopharmaceutical. The n.c.a. agent gave improved tumour uptake but also significantly greater accumulation in normal tissues known to accumulate MIBG such as heart, adrenal and skin. However, uptake and retention in the blood was unaltered. For all tissues examined, the 3-day calculations were undertaken to predict organ to tumour dose ratios which would result in human neuroblastoma patients with each of the [131I]MIBG preparations. These results suggest that significant therapeutic gain may be achieved by the use of n.c.a. [131I]MIBG as a treatment agent in neuroblastoma. neuroblastoma.

3-Iodobenzylguanidine↗
PubMed1995

Placental control of fetal growth.

The placenta exerts its effects on the growth of the fetus from the beginning of pregnancy via metabolic and endocrine mechanisms. To achieve this, the placenta exchanges a wide array of nutrients, endocrine signals, cytokines and growth factors with the mother and the fetus. These exchanges modulate or programme fetal growth and development. This review concentrates on the function and structure of the placenta in humans and in animals, and the effects of experimental perturbation of placental size and function on fetal growth. The consequences for fetal growth of varying the abundance of peptides or, by deleting genes, insulin-like growth factors or cytokines, are also described. Maternal nutritional and hormonal state from as early as the first few days after fertilization, can influence the growth rate of the placenta and the fetus and also the length of gestation. Influences on placental development and their consequences will clearly have an impact on the placental control of fetal growth. Variations in the maternal environment and consequent perturbation of the metabolic and endocrine environment of the placenta and fetus are implicated as being responsible for the associations between prenatal growth of the placenta and its fetus and the subsequent risk of adult disease. The next challenge will be to determine the dominant influences at each stage of fetal and placental growth.

Animals↗
PubMed1995

Fetal plasma insulin-like growth factor-binding protein-3 concentrations are elevated following bilateral nephrectomy in fetal sheep.

Insulin-like growth factors mediate many of the effects of growth hormone and are important in the regulation of growth, especially in the fetus where growth is less dependent on circulating growth hormone. In the ovine fetus, insulin-like growth factor-I (IGF-I) is bound mainly to the low molecular weight insulin-like growth factor-binding proteins (IGFBP), IGFBP-1 and IGFBP-2, with little binding to IGFBP-3 until near term at 147 days gestation. To determine if there was any difference in plasma IGF-I and IGFBP-3 concentrations in growth-retarded fetal sheep with altered renal status, concentrations were measured by specific radioimmunoassay from bilaterally nephrectomized fetal sheep between Days 113 and 135 gestation. Plasma IGFBP-3 concentrations were significantly (P < 0.001) increased in bilaterally nephrectomized fetuses (4.19 +/- 0.19 micrograms mL-1, n = 7) compared with control fetuses (2.33 +/- 0.10 micrograms mL-1, n = 7). There was no change in plasma IGFBP-3 concentration with gestational age in either experimental group. Maternal plasma IGFBP-3 concentrations did not differ between the bilateral nephrectomy group (3.11 +/- 0.09 micrograms mL-1, n = 7) and the control group (3.25 +/- 0.11 micrograms mL-1, n = 7) and showed no change within groups over the experimental period. Total plasma IGF-I concentrations in bilaterally nephrectomized fetuses and ewes were similar to those in control fetuses and ewes. The results indicate that the profile of IGF binding in fetal plasma is altered in the anephric fetal sheep. In nephrectomized fetal sheep, increased IGFBP-3 concentrations, and therefore increased IGF-binding capacity in fetal plasma, may have contributed to a decrease in free IGF in plasma and decreased IGF-I bioactivity. This would provide a possible mechanism for the growth retardation reported in bilaterally nephrectomized fetal sheep.

Animals↗
PubMed1995

No-carrier-added iodine-131-MIBG: evaluation of a therapeutic preparation.

UNLABELLED: Iodine-131-metaiodobenzylguanidine ([131I]MIBG) is a radiopharmaceutical for imaging as well as targeted radiotherapy of neuroblastoma. It is predicted that the use of no-carrier-added [131I]MIBG, rather than the conventional low specific activity preparation, will result in an enhanced therapeutic ratio because of different transport processes in neuroblastoma compared with most normal tissues. METHODS: The main aims of the study were: (1) to determine whether [131I]MIBG of substantially greater specific activity is transported into tumor cells by the same process as the existing compound; (2) to evaluate the effect of nonradiolabeled MIBG on the cytotoxicity of no-carrier-added [131I]MIBG; and (3) to compare the biodistribution of both preparations of the radiochemical in neuroblastoma xenografts. RESULTS: Active uptake of no-carrier-added [131I]MIBG was temperature-, sodium- and oxygen-dependent; ouabain- and desmethylimipramine-inhibitable; and could be blocked competitively by monoamine inhibitors of the noradrenaline transport mechanism. The rank order of specific uptake capacity in a panel of neuroblastoma cell lines was the same for both low and high specific activity drug. Neuroblastoma spheroid regrowth was 85% inhibited by no-carrier-added [131I]MIBG at 2 MBq.ml-1. Inhibitory potency was reduced in a dose-dependent manner by nonradiolabeled MIBG. The accumulation of no-carrier-added [131I]MIBG was significantly greater in tumor, adrenal, heart and skin of tumor-bearing mice than that of the conventional therapy preparation of [131I]MIBG. CONCLUSION: These data indicate that there may be clinical advantages in the use of no-carrier-added [131I]MIBG rather than conventional [131I]MIBG.

3-Iodobenzylguanidine↗
PubMed1994

Carrier-free 131I-meta-iodobenzylguanidine: comparison of production from meta-diazobenzylguanidine and from meta-trimethylsilylbenzylguanidine.

Meta-iodobenzylguanidine (MIBG) is a drug which is selectively accumulated by the uptake-1 process in adrenergic tissues. When labelled with 131I, it may be used for the targetted radiotherapy of tumours such as phaeochromocytoma and neuroblastoma. This paper describes the preparation of carrier-free 131I-MIBG by radioiodination of meta-diazobenzylguanidine, and compares this process with one involving iododesilylation of meta-trimethylsilylbenzylguanidine. Both processes result in the formation of carrier-free 131I-MIBG whose specific activity at greater than 3 x 10(16) Bq mol-1 is at least 100 times higher than that of commercially available 131I-MIBG for therapeutic use. The therapeutic use of 131I-MIBG with a higher than usual specific activity is predicted to result in a greater target-to-nontarget ratio, and therefore enhanced efficacy because of an increased therapeutic index. As the radiochemical yield of the process involving the metadiazobenzylguanidine intermediate is only 13%, compared with 98% for the iododesilylation reaction, the latter is the preferred synthetic route.

3-Iodobenzylguanidine↗
PubMed1994

Characterization of the binding of [3H]substance P to the nicotinic acetylcholine receptor of Torpedo electroplaque.

The binding of [3H]substance P to nicotinic acetylcholine receptor-enriched Torpedo electroplaque membranes was characterized. In the absence of cholinergic agonist, [3H]substance P binding was displaced by unlabeled substance P with an IC50 of 31 +/- 7 microM. In the presence of 10 mM carbamylcholine, displacement reflected two populations of binding sites with IC50 values of 0.93 +/- 0.39 and 30 +/- 5 microM, with the higher affinity component contributing 69 +/- 2% of the inhibition. Equilibrium binding parameters were calculated by transformation of the concentration dependences of inhibition into saturation isotherms. In the absence of agonist, substance P bound with a Kd of 42 +/- 7 microM to 3-4 sites/alpha-bungarotoxin binding site. In the presence of agonist, substance P bound to two sites, a low affinity site not significantly different from that seen in the absence of agonist (Kd = 25 +/- 8 microM, approximately 3 sites/alpha-bungarotoxin site) and a high affinity site with a Kd of 0.55 +/- 0.32 microM (approximately 1 site/2 alpha-bungarotoxin sites, 1 site/receptor). The increase in substance P binding induced by carbamylcholine was blocked by the nicotinic antagonists alpha-bungarotoxin and d-tubocurarine but was not affected by the muscarinic antagonist atropine. The concentration dependence of the carbamylcholine-induced increase had two components, with EC50 values for the agonist of 9.1 +/- 4.2 microM (56 +/- 16% of the increase) and 1.3 +/- 0.5 mM. The structural specificity of agonist-dependent high affinity substance P binding was identical to that seen for inhibition of nicotinic receptor activation and substantially different from that of binding to the G protein-coupled tachykinin receptors. From the time courses of association, it appears that substance P binds preferentially to a transient agonist-induced receptor state. The gamma and delta subunits of the receptor were specifically labeled in an agonist-dependent manner after cross-linking of [3H]substance P to the receptor with the bifunctional cross-linking reagent bis[2-(succinimidooxycarbonyloxy)ethyl]sulfone or after photoaffinity labeling of the receptor with 125I-p-benzoylphenylalanine-substance P. These results demonstrate the existence of a high affinity agonist-induced binding site for substance P on the nicotinic acetylcholine receptor that probably mediates the noncompetitive inhibition by the peptide of receptor activation.

Affinity Labels↗
PubMed1993

Macrophage colony-stimulating factor (M-CSF) induces migration in osteoclasts in vitro.

It has recently been shown that M-CSF is essential for osteoclast formation and survival. Paradoxically, the cytokine inhibits bone resorption by isolated osteoclasts. This implies that it may stimulate some function in osteoclasts not directly related to the bone resorptive process itself. We now report that M-CSF stimulates migration in isolated rat osteoclasts. This was achieved predominantly by a 3-8-fold increase in the proportion of osteoclasts demonstrating migration, combined with an increase in the area of substrate covered (43-96%) by each migrating cell. This action of M-CSF on migration is the inverse of its effect on resorption, wherein it has been previously found to reduce the proportion of osteoclasts that resorb bone and suggests that migration and resorption might represent alternative states of osteoclast behaviour. The results also suggest that osteoblast-derived M-CSF might play a role in the induction and regulation of localisation of these cells in bone.

Animals↗