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Biomedical subjects

M Pearson

Publications and source records attributed to M Pearson.

At least 55 records · Page 3Linked to original sources
PubMed1998

A volumetric study of guided bone regeneration around titanium implants in the New Zealand white rabbit.

Previous studies have shown the ability for bone to grow under occlusive membranes. This study was undertaken to determine the time required for bone to form in the space created under the membrane and to determine the amount of bone that may be grown under the membrane. Thirty-two New Zealand white rabbits were divided into three groups. A Brånemark implant, having a diameter of 3.75 mm with a length of 7 mm, was placed in each tibia and Gore-Tex membrane was draped over the implant on the experimental side and tethered to the wound margin. Sixteen rabbits were sacrificed at six weeks, eight at twelve weeks, and eight at eighteen weeks. At six weeks the available space under the membrane was filled to 68 per cent, at twelve weeks it was 45 per cent, and at eighteen weeks 54 per cent. A comparison of bone height measurements on test and control sides showed a significant difference (p = 0.0001) at the three time intervals. A comparison of grown bone volumes (test vs control) was also statistically significant (p = 0.0001). The ability to grow bone under an occlusive membrane was confirmed but the long-term survival rate and ability to support load needs to be investigated.

Analysis of Variance↗
PubMed1998

The short-period mutant, toc1-1, alters circadian clock regulation of multiple outputs throughout development in Arabidopsis thaliana.

The coordination of developmental and physiological events with environmental signals is facilitated by the action of the circadian clock. Here we report a new set of circadian clock-controlled phenotypes for Arabidopsis thaliana. We use these markers together with the short-period mutant, toc1-1, and the clock-controlled cab2::luciferase reporter gene to assess the nature of the circadian clock throughout development and to suggest the position of TOC1 within the circadian clock system. In dark-grown seedlings, the toc1-1 lesion conferred a short period to the cycling of cab2::luciferase luminescence, as previously found in light-grown plants, indicating that the circadian clocks in these two divergent developmental states share at least one component. Stomatal conductance rhythms were similarly approximately 3 hours shorter than wild type in toc1-1, suggesting that a cell-autonomous clockwork may be active in guard cells in 5- to 6-week-old leaves. The effect of daylength on flowering time in the C24 ecotype was diminished by toc1-1, and was nearly eliminated in the Landsberg erecta background where the plants flowered equally early in both short and long days. Throughout a 500-fold range of red light intensities, both the wild type and the mutant showed an inverse log-linear relationship of fluence rate to period, with a 2-3 hour shorter period for the mutant at all intensities. These results indicate that TOC1 acts on or within the clock independently of light input. Temperature entrainment appears normal in toc1-1, and the period-shortening effects of the mutant remain unchanged over a 20 degrees C temperature range. Taken together our results are consistent with the likelihood that TOC1 codes for an oscillator component rather than for an element of an input signaling pathway. In addition, the pervasive effect of toc1-1 on a variety of clock-controlled processes throughout development suggests that a single circadian system is primarily responsible for controlling most, if not all, circadian rhythms in the plant.

Arabidopsis↗
PubMed1997

A double-blind placebo-controlled phase II trial of thalidomide in asymptomatic HIV-positive patients: clinical tolerance and effect on activation markers and cytokines.

A randomized double-blind, placebo-controlled study was performed to determine the safety, efficacy, and effect of thalidomide on a variety of immunological and biochemical parameters in asymptomatic human immunodeficiency virus (HIV)-positive patients. Nineteen male patients with elevated markers of immune activation and CD4 cell counts above 400/mm3 were randomized to either placebo or thalidomide at 100 mg/day for 24 weeks. However, only 3 (of 10) patients receiving thalidomide completed all 24 weeks compared to 6 (of 9) patients receiving placebo. This was mainly due to fatigue (somnolence is a recognized side effect), although this was also seen to a lesser extent in the placebo group and so may not be drug attributable. No significant changes in CD4/CD8 count, activation markers, TNF-alpha, or TNFR1 were observed. However, a nonsignificant trend toward inhibition of mitogen-induced TNF-alpha production was observed in the thalidomide arm. The lack of systemic effect and the lower tolerance of thalidomide (at this dose) in asymptomatic patients highlights the need for pharmacokinetic analysis to address possible absorption problems and the need for more potent and less toxic TNF-alpha inhibitors to be developed for use in this type of study.

Adult↗
PubMed1997

Cell death induction by the acute promyelocytic leukemia-specific PML/RARalpha fusion protein.

PML/RARalpha is the abnormal protein product generated by the acute promyelocytic leukemia-specific t(15;17). Expression of PML/RARalpha in hematopoietic precursor cell lines induces block of differentiation and promotes survival. We report here that PML/RARalpha has a potent growth inhibitory effect on all nonhematopoietic cell lines and on the majority of the hematopoietic cell lines tested. Inducible expression of PML/RARalpha in fibroblasts demonstrated that the basis for the growth suppression is induction of cell death. Deletion of relevant promyelocytic leukemia (PML) and retinoic acid receptor (RARalpha) domains within the fusion protein revealed that its growth inhibitory effect depends on the integrity of the PML aminoterminal region (RING, B1, B2, and coiled coil regions) and the RARalpha DNA binding region. Analysis of the nuclear localization of the same PML/RARalpha deletion mutants by immunofluorescence and cell fractionation revealed that the biological activity of the fusion protein correlates with its microspeckled localization and its association to the nuclear matrix. The PML aminoterminal region, but not the RARalpha zinc fingers, is required for the proper nuclear localization of PML/RARalpha. We propose that the matrix-associated microspeckles are the active sites of PML/RARalpha and that targeting of RARalpha sequences to this specific nuclear subdomain through PML sequences is crucial to the activity of the fusion protein on survival regulation.

3T3 Cells↗
PubMed1996

The PML/RAR alpha oncoprotein is a direct molecular target of retinoic acid in acute promyelocytic leukemia cells.

Acute promyelocytic leukemia (APL) is characterized by the translocation, t(15;17) and the expression of a PML/RAR alpha fusion protein that is diagnostic of the disease. There is evidence that PML/RAR alpha protein acts as a dominant negative inhibitor of normal retinoid receptor function and myeloid differentiation. We now show that the PML/RAR alpha fusion product is directly downregulated in response to retinoic acid (tRA) treatment in the human APL cell line, NB4. tRA treatment induces loss of PML/RAR alpha at the protein level but not at the level of mRNA, as determined by Northern blots, by Western blots, and by ligand binding assays and in binding to RA-responsive DNA elements. We present evidence that this regulation is posttranslational. This evidence suggests that tRA induces synthesis of a protein that selectively degrades PML/RAR alpha. We further show that this loss of PML/ RAR-alpha is not limited to the unique APL cell line. NB4, because PML/RAR alpha protein is selectively downregulated by tRA when expressed in the transfected myeloid cell line U937. The loss of PML/RAR alpha may be directly linked to tRA-induced differentiation, because in a retinoid-resistant subclone of NB4, tRA does not decrease PML/RAR alpha protein expression. In NB4 cells, the specific downregulation of the fusion protein decreases the ratio of PML/RAR alpha to wild-type RAR alpha. Because the ratio of expression of PML/RAR alpha to wild-type RAR alpha and PML may be important in maintaining the dominant negative block of myelocytic differentiation, these data suggest a molecular mechanism for restoration by tRA normal myeloid differentiation in APL cells.

Cell Differentiation↗
PubMed1996

Tumour angiogenesis as a prognostic marker in infiltrating lobular carcinoma of the breast.

The importance of angiogenesis, assessed by tumour microvessel density, as a marker of survival was examined in 160 patients with infiltrating lobular carcinoma of the breast (ILC). The median follow-up was 5.1 years. Of these patients, 46 were node-negative, 59 were node-positive, and in 55 the pathological lymph node status was not known. Tumour sections were immunohistochemically stained with Factor VIII-related antibody. Microvessels were identified using previously recommended methodology and counted in three separate fields, selected from areas of highest vascularity, at x 200 magnification (field area = 0.785 mm2). Only the highest count was considered in the analysis. No association was found between microvessel density and age, menopausal status, tumour size, histological subtype, peritumoural vessel invasion, and lymph node involvement at presentation. There was no association between microvessel density and overall survival or relapse-free survival. These results suggest that microvessel density assessment, using currently recommended methods, is unlikely to be of prognostic value in ILC.

Adult↗
PubMed1996

Cesarean childbirth and psychosocial outcomes: a meta-analysis.

A comprehensive literature review with meta-analysis examines the differences between vaginal and cesarean delivery on 23 psychosocial outcomes of childbirth. The most robust findings suggest that cesarean mothers, compared with mothers who delivered vaginally, expressed less immediate and long-term satisfaction with the birth, were less likely ever to breast-feed, experienced a much longer time to first interaction with their infants, had less positive reactions to them after birth, and interacted less with them at home. Some differences were also found between unplanned and planned cesarean sections; none were found between birthing methods for maternal confidence for infant caretaking soon after birth, maternal anxiety in the hospital and at home, maternal stress at home, maternal return to work, and continuation of breast-feeding once begun. Implications of these findings for theory, research, and childbirth practice are discussed.

Breast Feeding↗
PubMed1996

Gerogogy (ger-o-go-gee) in patient education.

As clients age, traditional teaching tools become ineffective. This article illustrates how integrating the client's age-related changes, present disease processes, level of education, and motivation into the teaching plan can facilitate learning.

Aged↗
PubMed1995

Voluntary anonymous linked study of the prevalence of HIV infection and hepatitis C among inmates in a Canadian federal penitentiary for women.

OBJECTIVE: To determine the seroprevalence of HIV infection and hepatitis C among inmates of a federal penitentiary for women. DESIGN: Voluntary, anonymous, linked, point-prevalence study involving testing of blood samples for antibodies to HIV and hepatitis C virus. PARTICIPANTS: All inmates of the multilevel security federal Prison for Women, Kingston, Ont., who volunteered to participate in the study. Inmates at this long-stay facility are from across Canada. OUTCOME MEASURE: Seroprevalence rate among participants of antibodies to HIV and hepatitis C virus. RESULTS: Of the 130 inmates available for study 113 (86.9%) agreed to donate a blood sample. One woman (0.9%) was HIV positive; 45 (39.8%) were positive for hepatitis C antibody. CONCLUSIONS: It is possible to obtain a high participation rate in a voluntary, anonymous, linked point-prevalence study in a long-stay penitentiary. The HIV seroprevalence rate of 0.9% is lower than that found in studies in provincial (short-stay) prisons. However, the high rate of antibodies to hepatitis C suggests a significant level of risk behaviour, most likely injection drug use, and suggests the potential for a rapid increase in the rate of HIV infection should the number of newly admitted HIV-positive inmates who use injection drugs rise.

Adolescent↗
PubMed1995

Right gastroepiploic-to-coronary artery bypass. The first decade of use.

BACKGROUND: The right gastroepiploic artery was first used by us as a coronary artery bypass graft (CABG) in June 1984 and has become an accepted alternative conduit for myocardial revascularization. METHODS AND RESULTS: We have now performed this operation in 126 patients (111 of whom were men) aged 32 to 78 years. The right gastroepiploic artery was used as a pedicle graft to the right main coronary artery in 25 patients, to its posterior descending branch in 90, to a left ventricular branch in 2, to branches of the circumflex system in 6, and to the left anterior descending artery in 1. Free (aortocoronary) gastroepiploic grafts were placed to circumflex branches in 2 patients. There were 2 hospital deaths (stroke, arrhythmia), and mean +/- SD postoperative stay was 7.5 +/- 2.0 days. All survivors were symptomatically improved and are functionally in New York Heart Association functional class I or II. There have been 3 late deaths (at 34, 50, and 84 months) in 2 to 120 months of follow-up (mean, 41.4 months). Angiography of bypass grafts and coronary arteries was performed in 44 patients at 7 days to 80 months postoperatively, providing direct evidence of gastroepiploic graft patency in 34 patients and strong indirect evidence in another 6; adequate data could not be obtained in 3 patients for technical reasons, and 1 graft was occluded. CONCLUSIONS: These short-term, intermediate, and long-term results demonstrate the suitability of the right gastroepiploic artery as a CABG. The use of the right gastroepiploic artery as a graft to coronary arteries on the posterior wall of the heart, in conjunction with one or both internal mammary arteries, has the potential to allow complete myocardial revascularization with viable arterial grafts.

Adult↗
PubMed1995

Appropriateness of hospital use in the United Kingdom: a review of activity in the field.

OBJECTIVE: This paper reviews experience, in both research and application, with measures of appropriateness applied to the utilization of hospital inpatient services in the UK. BACKGROUND: The evolution of different methods for measuring appropriateness of use and the associated reasons for misutilization are described. RESEARCH AND APPLICATION: Recent research developments and applications are outlined and discussed. CONCLUSION: Contemporary enthusiasm with "Diagnosis Independent Explicit Criteria Utilization Review Instruments" is observed and some of the underlying influences are explored.

Health Services Research↗
PubMed1995

Effects of ozone on growth and gas exchange of Eucalyptus globulus seedlings.

To study the effects of a low concentration of ozone on growth and gas exchange in Eucalyptus globulus Labill. seedlings, ozone was applied for 37 days at a concentration of 50 ppb for 7 h daily under conditions of low light (250 micro mol m(-2) s(-1) (PAR)) and controlled temperature (20 degrees C). The seedlings exhibited extreme sensitivity to ozone. The ozone treatment reduced total plant biomass but had no effect on the partitioning of assimilate. Photosynthesis, stomatal conductance and internal CO(2) concentration were all reduced by ozone. The decline in photosynthesis was partly the result of direct effects of ozone on the stomata.

Journal Article↗
PubMed1995

Alterations in nutritional status and disease activity during treatment of Crohn's disease with elemental diet.

BACKGROUND: The mechanisms by which elemental diets induce remission in patients with Crohn's disease is unknown, but it has been suggested that improvement in nutritional state may play a part. METHODS: We assessed sequential changes in disease activity (clinical and laboratory indices and faecal excretion of indium-111-labelled leucocytes) and nutritional status (anthropometry, body composition variables), hepatic secretory proteins (albumin, pre-albumin, transferrin), and trace elements (iron, magnesium, copper, zinc) during treatment of acute Crohn's disease with an elemental diet. RESULTS: Disease activity indices improved significantly by 2 weeks and were maintained at 4 weeks of treatment. There was a significant increase in pre-albumin at 4 weeks and an increase in serum iron and a decrease in serum copper during the study period. The changes occurring in the measures of nutrition did not correlate significantly with the changes in disease activity. CONCLUSION: The fact that changes in disease activity appear to precede any detectable changes in nutritional state, it suggests that the beneficial action of elemental diet in patients with active Crohn's disease is not due to an improvement in nutritional status.

Adolescent↗