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Biomedical subjects

A Thornton

Publications and source records attributed to A Thornton.

At least 37 records · Page 2Linked to original sources
PubMed2000

Publication bias in meta-analysis: its causes and consequences.

Publication bias is a widespread problem that may seriously distort attempts to estimate the effect under investigation. The literature is reviewed to determine features of the design and execution of both single studies and meta-analyses leading to publication bias, and the role the author, journal editor, and reviewer play in selecting studies for publication. Methods of detecting, correcting for, and preventing publication bias are reviewed. The design of the meta-analysis itself, and the studies included in it, are shown to be important among a number of sources of publication bias. Various factors influence an author's decision to submit results for publication. Journal editors and reviewers are crucial in deciding which studies to publish. Various methods proposed for detecting and correcting for publication bias, though useful, all have limitations. However, prevention of publication bias by registering every trial undertaken or publishing all studies is an ideal that is hard to achieve.

Epidemiologic Research Design↗
PubMed2000

Immunohistochemical evidence for mesothelial origin of paratesticular adenomatoid tumour.

AIMS: To investigate the histogenesis of paratesticular adenomatoid tumour by use of immunohistochemical markers for a variety of carcinomas and mesothelioma. METHODS AND RESULTS: Immunohistochemical staining of sections from 12 cases of paratesticular adenomatoid tumour was undertaken using primary antibodies to antigens expressed by benign epithelial cells and carcinoma (cytokeratin AE1/AE3, cytokeratin 34ssE12, epithelial membrane antigen, MOC-31, Ber-EP4, CEA, B72.3, LEA.135, Leu M1), stromal and vascular markers (vimentin, CD34, factor VIII), and mesothelioma-associated antigens (thrombomodulin, HBME-1, OC 125) and p53 protein. There was absence of immunohistochemical expression of epithelial/carcinoma markers MOC-31, Ber-EP4, CEA, B72.3, LEA.135, Leu M1 and to factor VIII and CD34. All tumours expressed cytokeratin AE1/AE3, epithelial membrane antigen and vimentin, with weak expression of cytokeratin 34ssE12 in 25% of tumours. Each tumour showed expression of thrombomodulin, HBME-1 and OC 125 in a membranous distribution. p53 protein expression was not detected. CONCLUSIONS: The immunohistochemical profile of paratesticular adenomatoid tumour is strongly supportive of a mesothelial cell origin.

Adenomatoid Tumor↗
PubMed2000

Effect of a full and empty bladder on radiation dose to the uterus, ovaries and bladder from lumbar spine CT and X-ray examinations.

This is a quantitative study of the effect of a full and empty bladder on the position of the uterus, ovaries and bladder relative to the lumbar spine. Data are used to estimate the difference in radiation dose to these organs from performing a lumbar spine CT investigation or a lateral lumbar spine radiograph with a full bladder compared with an empty bladder. 12 women of child-bearing age underwent pelvic magnetic resonance scans with full and empty bladders. The positions of the uterus, ovaries and bladder were matched with the radiation dose distribution that would have occurred either side of the inferior boundary of the CT scan volume and the lateral lumbar spine radiograph. These radiation dose profiles were measured on phantoms using a combination of ionization chambers and thermoluminescent dosemeters. When the bladder was emptied, the mean position of the endometrial cavity fundal tip moved from 4.1 cm to 6.1 cm inferior to the centre of the L5/S1 disc space, and from 0.87 cm to 1.12 cm anterior to the centre of the L5/S1 disc space. This movement on micturation would have reduced the mean dose to the uterine internal fundal tip during a pelvic CT scan from 6.8 mGy to 3.9 mGy, which represents a mean reduction of 43% (range 12-67%). The mean dose from a lateral lumbar spine examination would have been reduced from 197 microGy to 126 microGy. The change in ovary position results in the mean ovary dose being reduced by 48% for the lumbar spine CT scan and by 43%) for a lateral lumbar spine radiograph. When the bladder was emptied, the average position of the bladder wall moved from 7.2 cm to 10.3 cm inferior to the L5/S1 disc space. This change in bladder position reduces the mean dose to the wall of a full bladder from 5.7 mGy for a CT scan and 114 microGy for a lumbar spine radiograph to 2.2 mGy and 42 microGy, respectively, for an empty bladder.

Adult↗
PubMed2000

Influence of HLA matching and associated factors on aortic valve homograft function.

BACKGROUND AND AIM OF THE STUDY: Evidence suggests that the implanted aortic valve homograft suffers eventual loss of function due to early donor-specific antibody and T cell-mediated responses to human leukocyte antigens (HLA). The association between rejection/dysfunction and donor/recipient HLA mismatch for vascularized organ homografts has not been revealed for aortic valve homografts. An aortic valve homograft recipient cohort was studied to determine whether HLA mismatch and associated factors predicted homograft dysfunction. METHODS: Both donor and recipient HLA type was obtained for 162 recipients of cryopreserved aortic valve homografts between 1986 and 1998. Structural deterioration of the homograft was defined by echocardiography as at least moderate aortic stenosis or regurgitation. Patients' records were searched for postoperative fever, ABO blood type disparity, and other associated factors. HLA class 1 (A and B antigens) were typed serologically, and HLA class 2 (DR antigens) by molecular genotyping. Associations were analyzed using chi-square tests and Kaplan-Meier curves of freedom from structural deterioration in all patients, and in those with > or =5 years of follow up. Cox regression was used to determine independent predictors of structural deterioration. RESULTS: Class 2 antigen mismatch had a significant association (p = 0.04) with decrease in cryopreserved aortic valve homograft freedom from structural deterioration in patients with long-term follow up (> or =5 years). In addition, there was an important difference in frequency of postoperative fever in recipients with two DR mismatches (31.2%), and in those with no or one DR mismatch (16.9%; p = 0.051). Significant associations were not found between homograft dysfunction and HLA mismatch at the class-1 loci. Young age at operation and short time (<4 h) between homograft procurement and cryopreservation were associated with an increase in structural deterioration. CONCLUSION: The association between aortic valve homograft dysfunction and HLA DR mismatch suggests that elements of the anti-donor immune response penetrate and damage the homograft. A similar link to postoperative fever indicates that immune stimulation may be an early event. Further investigation will reveal the exact pathways by which this occurs and by which therapy (immunosuppression of the recipient, genetic engineering of the donor graft, or other techniques) this recipient anti-donor response can be modified.

ABO Blood-Group System↗
PubMed1999

Stereotactic proton radiosurgery.

The technique of stereotactic proton radiosurgery is discussed in depth in this article. The physics of the proton beam in radiosurgery is explained, and the different factors of beam delivery are examined. These key factors (correspondence to shape, accuracy of delineation of volume, correspondence to volume, and accuracy of delivery vary) with each of the radiosurgical techniques, from Gamma Knife surgery to linear accelerator therapy. Clinical series in the use of proton radiosurgery are also presented, with an emphasis on efficacy and uses.

Biophysical Phenomena↗
PubMed1999

Unwanted childbearing, health, and mother-child relationships.

This paper investigates the relationships among unwanted childbearing, health, and mother-child relationships. We hypothesize that unwanted childbearing affects mother-child relationships in part because of the physical and mental health consequences of unwanted childbearing. Impaired mental health hampers women's interaction with their infants, and these poor neonatal relationships translate into poor mother-adult child relationships. Using the Intergenerational Panel Study of Mothers and Children--a 31-year longitudinal survey of a probability sample of 1,113 mother-child pairs begun in 1961--we demonstrate that mothers with unwanted births have lower quality relationships with their children from late adolescence (age 18) throughout early adulthood (ages 23 and 31). Furthermore, these lower quality relationships are not limited to the child born as a result of the unwanted pregnancy; all the children in the family suffer. Using the 1987-88 wave of the National Survey of Families and Households, a survey of a national probability sample of U.S. households, we show that mothers with unwanted births suffer from higher levels of depression and lower levels of happiness. We also demonstrate that they spank their young children more and spend less leisure time with them. We conclude that experiencing unwanted childbearing reduces the time and attention that mothers give their young children and that these early mother-child interactions set the stage for long-term, lower quality relationships.

Adolescent↗
PubMed1998

T lymphocyte-mediated control of autoimmunity.

Autoreactive T cells can be readily identified in the peripheral lymphocyte pool of both humans and experimental animals. Peripheral tolerance may be maintained by regulatory/suppressor T cells which prevent the activation of autoantigen-specific cells. Mice thymectomized on day 3 of life (d3Tx) develop a wide spectrum of organ-specific autoimmune diseases. Reconstitution of d3Tx mice with CD4+ CD25+ T cells from normal mice prevents the development of disease. Similarly, CD4+ CD25+ T cells prevent the transfer of disease by autoantigen-specific cloned T cells derived from d3Tx mice. Thus, regulatory T cells can prevent both the induction and effector function of autoreactive T cells. In vitro, the CD4+ CD25+ population is anergic to stimulation through the T cell receptor (TCR) and suppresses the proliferative responses of normal CD4+ CD25- cells by a contract-dependent mechanism. Suppression is not MHC-dependent, but requires activation of the CD4+ CD25+ population. The mechanism of suppression in vivo and the target antigen(s) of this unique regulatory population remain to be characterized.

Adoptive Transfer↗
PubMed1998

Would thyroid and breast shielding be beneficial in CT of the head?

Contrary to common perception, the advent of third- and fourth-generation scanners has lead to a significant increase in radiation dose to the patient per computed tomography (CT) head scan. With that in mind, a pilot study was designed with the objective of assessing the effectiveness of a dental-style protective bib in reducing the dose to the radiosensitive organs of the neck and thorax. Radiation doses over the thyroid gland and breast were measured with thermoluminenscent dosemeters and an ionization chamber respectively in 110 patients undergoing routine head scans. Half the patients wore the protective bib and collar. With lead protection, the thyroid measurements were reduced by an average of 45 % and the breast measurements by an average of 76 %. Similar results were seen in phantom measurements.

Breast↗
PubMed1998

Netting in Nepal: social change, the life course, and brideservice in Sangila.

"Using survey and ethnographic data gathered in Nepal, this paper examines the implications of change in work, living experiences, and the marriage process for subsequent inter-familial relationships exemplified by cross-cousin marriage and the provision of brideservice. Hypotheses are developed which consider the impact of community context on these behaviors; these are tested in logistic regression analyses for the first marriages of all 430 ever-married women in the community. Cross-cousin marriage and brideservice are shown to be related to prior familial characteristics, life-course experience, and elements of the marriage process in ways that are significantly conditioned by community history and proximity to urban centers."

Asia↗
PubMed1998

The long-term impact of parents' childbearing decisions on children's self-esteem.

We examine the long-term impact of parents' childbearing decisions on children's self-esteem. We focus on subjective aspects of the home environment in the creation of children's internalized sense of self-worth. Unique 23-year family panel data combining measures of mothers' childbearing, mothers' childbearing intentions, and children's self-esteem allow us to examine the overall links between parents' childbearing and children's self-esteem. The results demonstrate that parents' childbearing intentions can have a significant long-term impact on their children's self-esteem. Children who were unintended by their mothers have significantly lower self-esteem 23 years later. Our findings indicate that giving birth to an unintended child can have a long-term negative impact on subjective aspects of the child's well-being, at least in terms of self-esteem. Unintended childbearing has received an increasing amount of research attention in recent years.

Adolescent↗
PubMed1997

Prognostic significance of microscopic vascularity for clear cell renal cell carcinoma.

OBJECTIVE: To investigate the association between tumour vascularity and patient survival in a series of clear-cell renal cell carcinoma (RCC), which often metastasizes via the vascular route and frequently has a prominent vascular network. MATERIALS AND METHODS: Vessels were labelled in sections from 150 cases of clear cell RCC by factor VIII immunohistochemistry. The mean microvessel density (MMD), expressed as the number of vessels per 10 high-power fields (HPFs, x400, aggregate field area 1.452 mm2) and tumour microvessel area (TMA), expressed as the percentage of the total tumour area within 10 HPFs, were measured for each case. The relationship between MMD and TMA, tumour stage and grade, and patient survival over a 5-year follow-up was determined. RESULTS: Tumour MMD ranged from 1 to 238 vessels per HPF, while the TMA was 1.2-60.8%. There was a weak but significant difference for MMD between tumour grades (P < 0.01) and stages (P < 0.05). There was no significant association between TMA and either tumour stage or grade. Division of cases according to MMD < or = 40 and > 40 per HPF showed a significant difference in survival curves between both groups, with a higher MMD being associated with longer patient survival. The significant association between MMD and survival was retained for stage 3 tumours only when cases were stratified according to Robson's stage at presentation. TMA did not correlate with survival. CONCLUSIONS: The assessment of tumour vascularity is of prognostic significance for clear cell RCC. The significant inverse relationship between MMD and patient survival suggests that for tumours with a poor prognosis, decreased MMD is associated with tumour fibrosis and the development of large diameter vascular channels.

Adenocarcinoma, Clear Cell↗
PubMed1997

Polyclonal Ki-67 expression in transitional cell carcinoma of the bladder.

The proliferation kinetics of 101 cases of transitional cell carcinoma (TCC) and seven cases of transitional cell carcinoma-in-situ of the bladder were assessed following staining with polyclonal Ki-67 antibody (pKi-67). Labeling indices ranged from 49% to 60.2% with a mean value of 22.2% for all cases. A significant association between pKi-67 indices, tumor grade and tumor stage was observed, with significant differences between pKi-67 indices of Grade 1 and 3 tumors and Grade 2 and 3 tumors. Significant differences in labeling indices were also found between superficial (Ta) tumors and both musculoinvasive (T2/T3a) tumors and those infiltrating the perivesical fat (T3b). pKi-67 indices for carcinoma-in-situ were similar to those noted for Grade 1 TCC. No difference in pKi-67 index was found when tumors were classified according to the morphology of the tumor invasion front. It is concluded that pKi-67 index is a useful marker for tumor progression for vesical TCC and that this immunohistochemical stain may assist clinical assessment of the potential behaviour of tumors in individual cases.

Antigens, Neoplasm↗
PubMed1997

Orthographic analogies and developmental dyslexia.

Goswami (1986, 1988) has demonstrated that children can use orthographic analogies (particularly at the onset-rime level) between the spelling patterns in words to help to decode new words (e.g. using 'beak' to read 'peak'). This strategy has been shown in children as young as six years old. Since it is known that children with developmental dyslexia find it particularly difficult to read words that they have not been specifically taught (Lovett, Warren-Chaplin, Ransby & Borden, 1990), the present study investigated whether dyslexic children might be unable to use analogies. Employing a design similar to that used by Goswami (1988), it was hypothesized that dyslexics would find it difficult to transfer spontaneously knowledge of a 'clue' word to decode new words that could be read by analogy with the clue word. The results of Expt 1 indicated that the dyslexic readers read significantly fewer of the analogous words than a reading age-matched comparison group of younger children. Furthermore, none of the nine dyslexic children read as many of the analogous words as the lowest scoring control child. In a second experiment, a design similar to that of Muter, Snowling & Taylor (1994) was used with a new and larger sample of dyslexic children. In this experiment, all the children were brought to criterion in reading the clue words before the analogous words were presented. Once again, the dyslexic children read significantly fewer words that were analogous with the clue words than did a reading age-matched comparison group. The number of analogous words that the dyslexic children read was significantly correlated with their performance on a test that is sensitive to the ability to detect rhyme. It is argued that a failure to make analogies may be one of the main causes of the reading impairment experienced by children with developmental dyslexia.

Child↗