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Biomedical subjects

A Johnson

Publications and source records attributed to A Johnson.

At least 19 recordsLinked to original sources
PubMed2007

In vitro biocompatibility of fluorcanasite glass-ceramics for bone tissue repair.

Fluorcanasite glass-ceramics were produced by controlled two stage heat-treatment of as-cast glasses. These glasses were modified from stoichiometric fluorcanasite composition by either adding P(2)O(5) or altering the molar ratios of Na(2)O and CaO. Commercial bioactive 45S5 Bioglass(R) was also prepared in-house to evaluate the relative in vitro biocompatibility of fluorcanasite glass-ceramics. The scanning electron microscopy (SEM) images showed that cells had colonized the surfaces of fluorcanasite glass-ceramics to form a confluent sheet. Quantitative MTT assay results were in good agreement with the qualitative SEM observations. It was concluded that incorporation of excess calcium oxide or P(2)O(5) in stoichiometric glass composition improved in vitro biocompatibility. Controlled heat-treatment further improved the biological response of cultured bone cells to modified fluorcanasite glass-ceramics when compared with their parent glasses. Ion release and pH data suggested a strong correlation between solubility (in particular, Na ion release) and biocompatibility. Reduced solubility, Na ion release, and related pH effects appeared to be the principal mechanisms responsible for improvement in in vitro biocompatibility.

Animals↗
PubMed2006

Caesarean section surgical site infection surveillance.

Surveillance of surgical site infection (SSI) is an important infection control activity. The Caesarean section procedure was selected, as part of the Scottish Surveillance of Healthcare Associated Infection Programme, to monitor and report upon the incidence of SSI. Data were collected prospectively for 715 patients undergoing a Caesarean section procedure for 35 weeks during the latter months of 2002 and the first quarter of 2003. Of these, 80 (11.2%) patients developed an SSI, 57 (71%) of which were detected by postdischarge surveillance. Risk factors associated with infection were analysed. The choice of subcuticular suture rather than staples to close the surgical site was associated with a significantly lower incidence of infection (P=0.021). Obese women experienced significantly more infections than women with a normal body mass index (P=0.028). Dissemination of the surveillance results has made clinicians aware of the influence of body mass index and choice of skin closure in relation to SSI in this patient population. Analysis of these data has led to a review of local practice. The results also indicate the importance of postdischarge surveillance if SSIs are to be detected in this patient group. Continuous data collection and timely dissemination of the results are important factors acting as the catalyst for a review of practice.

Adult↗
PubMed2006

The effects of Scaphoid and Colles casts on hand function.

Although necessary for bone healing, immobilisation temporarily prevents hand function and may necessitate corrective physiotherapy later. Scaphoid and Colles casts are both commonly used to immobilize scaphoid fractures. Non-union rates are comparable with both casts. The Scaphoid cast incorporates the thumb, whereas the Colles cast leaves the thumb free. We compared the effect of the two casts on hand function in 20 healthy right-hand-dominant volunteers using the Jebsen-Taylor Hand Function Test. Data were obtained through a mixed between and within subject design. Both casts prolonged the time taken to complete the hand function test compared to controls. Testing in the Scaphoid cast took significantly longer than in the Colles cast.

Adult↗
PubMed2006

FGF ligand family mRNA expression profile for mouse preimplantation embryos, early gestation human placenta, and mouse trophoblast stem cells.

Signaling by fibroblast growth factor (FGF) is essential is for trophoblast stem (TS) cells and preimplantation embryos. FGF4 provides essential signaling, but the expression of the complete set of 23 FGF family members has not been analyzed. Here, semi-quantitative RT-PCR and microarray analyses were used to define expression of all FGF ligand mRNA. RT-PCR was done for developmentally important FGF subfamilies, FGF10/FGF22 and FGF8/FGF17/FGF18 as well as FGF11. FGF4 and FGF18 are detected at highest levels by RT-PCR and microarrays. FGF10 was detected at low levels in both assays. FGF11 was detected at moderate levels by microarray, but not by RT-PCR. FGF17 was detected at low levels by array and moderate levels by RT-PCR. FGF8 and FGF22 were detected by RT-PCR, but not by microarrays during late cleavage divisions. FGF8, FGF5, and FGF9 were detected in the oocyte by microarray. FGF2, FGF3, and FGF7 were not detected by RT-PCR or microarrays and FGF13, FGF14, and FGF23 were not detected by microarray. Since a major role of FGF is to maintain TS cells, we tested human and mouse placental cell lines and early gestation human placenta for expression of FGF ligands. Expression in mouse TS cells was compared with preimplantation embryos, and human placental cell line expression was compared with human placenta, to infer which ligands are expressed in placental lineage vs. other cell lineages. The data suggest that human and mouse placenta share FGF18 and its high expression suggests preimplantation and early placental function.

Animals↗
PubMed2006

Prenatal detection and evaluation of an extralobar pulmonary sequestration in the posterior mediastinum.

Extralobar pulmonary sequestration (EPS) is a rare developmental anomaly with aberrant nonfunctioning parenchymal tissue, associated with an increased risk of perinatal morbidity and, rarely, mortality owing to possible neonatal respiratory distress. In most cases supernumerary lobes are detected as isolated intra- or extrapleural lesions with independent systemic arterial blood supply. We report an atypical case of prenatal detection and perinatal outcome of a mediastinal EPS.

Adult↗
PubMed2006

A radioactive metal processing industry perspective source.

The current U.S. economic environment for the disposition of radioactive waste, including very-low-activity metals, is currently experiencing relatively low radioactive disposal costs and readily available disposal space. Despite the recent market increase in demand for recycled scrap metal commodities, there is still little change in the behavior of the nuclear industry (including radioactive waste processors and radioactive scrap metal recyclers) to pursue the recycling of potentially contaminated scrap metal. The relatively low cost of traditional radioactive waste disposal combined with the perceived risks associated with recycling of previously contaminated metals means that most U.S. radioactive facility managers and stakeholders will elect not to recycle. Current technology exists and precedence has been set for prescreening (by means of bulk radioactive assay techniques) scrap metal that is not contaminated and diverting it to industrial landfills for disposal. Other processes also allow some radiologically contaminated metals to be melted and recast into products with low, but acceptable, activity levels for restricted use in the nuclear industry. A new concept is being considered that would create a centralized licensed facility for the process and disposition of "very-low-activity" metals for "directed first use." The advantages to this type of approach would include a standardized method for licensing the clearance process.

Decision Making↗
PubMed2006

Change of refractive state and eye size in children of birth weight less than 1701 g.

AIMS: To determine the refractive status and ocular dimensions of a cohort of children at age 10-12 years with birth weight below 1701 g, and also the relation between the neonatal ophthalmic findings and subsequent refractive state. METHODS: 293 low birthweight children who had been examined in the neonatal period were assessed at 10-12 years of age. The examination consisted of autorefraction, keratometry, and A-scan. Results of right eyes were compared with published normative data. RESULTS: 293 of the birth cohort of 572 children consented to participate. The average mean spherical equivalent (MSE) in the low birthweight cohort was +0.691 dioptre, significantly higher than the control data (+0.30D, p = 0.02). The average change in MSE over the 10-12 year period was -1.00 dioptre (n = 256), but only 62.1% of cases showed a shift in refractive error of the appropriate magnitude and direction. The presence of any retinopathy of prematurity (ROP) increases the risk of developing anisometropia sixfold. CONCLUSIONS: Low birth weight and ROP both significantly impact the refractive state in the long term. At age 10-12 years children born preterm have an increased prevalence of all refractive errors. In low birthweight children refractive state is relatively stable over the first decade of life with a shift towards myopia of 1 dioptre.

Birth Weight↗
PubMed2006

Influence of family type and parenting behaviours on teenage sexual behaviour and conceptions.

BACKGROUND: Longitudinal data were used to explore relations between teenage pregnancy, sexual behaviour, and family type. The study examined whether students from lone parent and/or teenage mother initiated families more commonly report sex, lack of contraception at first sex, and/or conceptions by age 15/16, and whether such associations can be explained by low parental strictness, difficult parent-child communication, and/or low parental input into sex education. Up to date longitudinal UK research on family influences on conceptions is lacking, as is longitudinal research on family influences on sexual behaviour. No previous studies have comprehensively examined effects of parenting behaviours. Unlike previous research, this study tested theories suggesting that parenting deficits among lone parent and teenage initiated families increase risk of teenage pregnancy among their children. METHODS: Secondary analysis of data from a trial of sex education. RESULTS: Girls and boys from lone parent families or having mothers who were teenagers when they were born were more likely to report sex but not lack of contraception at first sex by age 15/16. Girls and boys with mothers having them as teenagers, and boys but not girls from lone parent families, were more likely to report being involved in conceptions by age 15/16. Only the association between teenage mother family and girls' conceptions was reduced by adjusting for a parenting behaviour measure. CONCLUSIONS: Students from lone parent families or having mothers who were teenagers when they were born are more likely to report early sexual debut and conceptions by age 15/16, but this is not generally explained by parenting style.

Adolescent↗
PubMed2005

How important is lateral masking in visual search?

Five experiments are presented, providing empirical support of the hypothesis that the sensory phenomenon of lateral masking may explain many well-known visual search phenomena that are commonly assumed to be governed by cognitive attentional mechanisms. Experiment I showed that when the same visual arrays are used in visual search and in lateral masking experiments, the factors (1) number of distractors, (2) distractor density, and (3) search type (conjunction vs disjunction) have the same effect on search times as they have on lateral masking scores. Experiment II showed that when the number of distractors and eccentricity is kept constant in a search task, the effect of reducing density (which reduces the lateral masking potential of distractors on the target) is to strongly reduce the disjunction-conjunction difference. In experiment III, the lateral masking potential of distractors on a target was measured with arrays that typically yield asymmetric search times in visual search studies (a Q among Os vs. an O among Qs). The lateral masking scores showed the same asymmetry. Experiment IV was a visual search study with such asymmetric search arrays in which the number of distractors and eccentricity was kept constant, while manipulating density. Reducing density (i.e., reducing lateral masking) produced a strong reduction of the asymmetry effect. Finally in experiment V, we showed that the data from experiment IV cannot be explained due to a difference between a fine and a coarse grain attentional mechanism. Taken together with eye movement data and error scores from experiment II and with similar findings from the literature, these results suggest that the sensory mechanism of lateral masking could well be a very important (if not the main) factor causing many of the well-known effects that are traditionally attributed to higher level cognitive or attentional mechanisms in visual search.

Attention↗
PubMed2005

Adipokines and the insulin resistance syndrome in familial partial lipodystrophy caused by a mutation in lamin A/C.

AIMS/HYPOTHESIS: Familial partial lipodystrophy (FPLD) and obesity are both associated with increased risks of type 2 diabetes and cardiovascular disease. Although adipokines have been implicated, few data exist in subjects with FPLD; therefore we investigated a family with FPLD due to a lamin A/C mutation in order to determine how abnormalities of the plasma adipokine profile relate to insulin resistance and the metabolic syndrome. METHODS: Plasma levels of adiponectin, leptin, resistin, IL-1beta, IL-6 and TNF-alpha in 30 subjects (ten patients, 20 controls) were correlated with indices of metabolic syndrome. RESULTS: Compared with controls, FPLD patients had significantly lower plasma levels of adiponectin (3.7+/-1.0 in FDLP cases vs 7.1+/-0.72 mug/ml in controls, p=0.02), leptin (1.23+/-0.4 vs 9.0+/-1.3 ng/ml, p=0.002) and IL-6 (0.59+/-0.12 vs 1.04+/-0.17 pg/ml, p=0.047) and elevated TNF-alpha (34.8+/-8.1 vs 13.7+/-2.7 pg/ml, p=0.028), whereas IL-1beta and resistin were unchanged. In both groups, adiponectin levels were inversely correlated with body fat mass (controls, r=-0.44, p=0.036; FDLP, r=-0.67, p=0.025), insulin resistance (controls, r=-0.62, p=0.003; FDLP, r=-0.70, p=0.025) and other features of the metabolic syndrome. TNF-alpha concentrations were positively related to fat mass (controls, r=0.68, p=0.001; FDLP, r=0.64, p=0.048) and insulin resistance (controls, r=0.86, p=0.001; FDLP, r=0.75, p=0.013). IL-6, IL-1beta and resistin did not demonstrate any correlations with the metabolic syndrome in either group. CONCLUSIONS/INTERPRETATION: Low adiponectin and leptin and high TNF-alpha were identified as the major plasma adipokine abnormalities in FPLD, consistent with the hypothesis that low adiponectin and high TNF-alpha production may be mechanistically related, and perhaps responsible for the development of insulin resistance and cardiovascular disease in FPLD.

Adiponectin↗
PubMed2005

Adenine nucleotide metabolism in human blood--important roles for leukocytes and erythrocytes.

Adenosine diphosphate (ADP) released into blood induces platelet aggregation and contributes to hemostasis and thrombosis. Released ATP can also induce platelet aggregation and there is evidence that blood leukocytes and also erythrocytes play important roles in this. Rapid metabolism of ADP and ATP by endothelial cells is important in protecting platelets from their effects. Here we have performed a systematic investigation of adenine nucleotide metabolism in human blood and the involvement of blood cells. Conversion of ATP to ADP in blood was due almost exclusively to the presence of leukocytes; plasma, platelets and erythrocytes made little or no contribution. Mononuclear leukocytes (MNLs) and polymorphonuclear leukocytes (PMNLs) were equally effective. Conversion of ADP to AMP was also promoted by leukocytes, with no involvement of platelets or erythrocytes. Some ADP was also converted to ATP in blood, apparently via an enzyme present in plasma, but ATP was then rapidly removed by the leukocytes. Conversion of AMP to adenosine occurred via a plasma enzyme with little or no contribution from any cellular element. As expected, in blood the adenosine produced was removed very rapidly by erythrocytes and then converted to inosine and then hypoxanthine. In the absence of erythrocytes plasma supported only a slow conversion of adenosine to inosine and hypoxanthine, which was not influenced by platelets or leukocytes. This study has demonstrated that leukocytes and erythrocytes play a major role in adenine nucleotide metabolism in blood and that these cells, as well as endothelial cells, may be important determinants of the effects of ATP and ADP on platelets.

Adenosine Diphosphate↗
PubMed2005

Structure-function analysis of a novel member of the LIV-1 subfamily of zinc transporters, ZIP14.

Here, we report the first investigation of a novel member of the LZT (LIV-1 subfamily of ZIP zinc Transporters) subfamily of zinc influx transporters. LZT subfamily sequences all contain a unique and highly conserved metalloprotease motif (HEXPHEXGD) in transmembrane domain V with both histidine residues essential for zinc transport by ZIP (Zrt-, Irt-like Proteins) transporters. We investigate here whether ZIP14 (SLC39A14), lacking the initial histidine in this motif, is still able to transport zinc. We demonstrate that this plasma membrane located glycosylated protein functions as a zinc influx transporter in a temperature-dependant manner.

Amino Acid Sequence↗
PubMed2005

My friend Dr Knox: a pupil writes about the anatomist.

Thomas Giordani Wright, a medical apprentice in Newcastle upon Tyne, attended Dr Robert Knox's anatomy classes in Edinburgh between November 1825 and April 1826, only two years before Burke and Hare began murdering people and selling the bodies of their victims to Knox's anatomy school. In March 1829, soon after the crimes came to light and Burke had been found guilty of murder and executed, Wright commented on the case in his diary, describing the practices in the dissection rooms and giving his views on Robert Knox, the teacher who had become his friend.

Anatomy↗
PubMed2005

Palatal discrepancies and postdams.

To investigate the variation in post-cure palatal discrepancy of dentures, 20 complete maxillary replica dentures were prepared on models with high and low palates and processed by conventional compression moulding and injection moulding. Measurements were made by travelling microscope of the sagittal midline discrepancies between palate and model on three occasions; after processing; after removal of part of the investing plaster; and after immersion in water for 1 month at 37 degrees C. The magnitudes of discrepancies were greatest distally, diminishing with distance anteriorly from the postdam. They increased with partial removal of plaster, and decreased slightly after immersion.

Acrylic Resins↗
PubMed2005

LARALink: a web application for cytogenetic linkage analysis.

Genomic and expression data have increased dramatically over the last several years. This is primarily due to the completion of the human genome project as well as an upsurge in the use of various high-throughput technologies. Recent attempts to correlate genomic and expression data have stimulated the scientific community to determine how this data can be used within a clinical setting (P Khatri et al., Genomics 2002: 79: 266; LJ van't Veer et al., Nature 2002: 415: 530). LARALink (Loci Analysis for Rearrangements Link) is a database-driven web application that utilizes several public datasets to analyze clinical cytogenetic data to identify candidate genes. LARALink allows UniGene clusters or single-nucleotide polymorphisms (SNPs) to be queried for multiple patients by cytoband, chromosome marker, or base pair. The results can be further refined with the use of an anatomical site, developmental stage, pathology, or cell-type expression filter. Once a set of UniGene clusters (expressed genes) has been identified either for a single patient or for a shared region among multiple patients, the expression-distribution profile, expressed sequence tags (ESTs), or online mendelian inheritance in man (OMIM) entries are displayed. The utility of this tool is shown by its application to both research and clinical medicine. LARALink is a public resource available at: http://www.laralink.bioinformatics.wayne.edu:8080/unigene.

Alzheimer Disease↗
PubMed2005

Case gender and severity in cerebral palsy varies with intrauterine growth.

BACKGROUND: There is an unexplained excess of cerebral palsy among male babies. There is also variation in the proportion of more severe cases by birth weight. It has recently been shown that the rate of cerebral palsy increases as intrauterine size deviates up or down from an optimum about one standard deviation heavier than population mean weight-for-gestation. AIMS: To determine whether the gender ratio or the severity of cases also varies with intrauterine size. METHODS: A total of 3454 cases of cerebral palsy among single births between 1976 and 1990 with sufficient data to assign case severity (based on intellectual impairment and walking ability) and to compare weight-for-gestation at birth to sex specific fetal growth standards, were aggregated from nine separate registers in five European countries. RESULTS: The greater the degree to which growth deviates either up or down from optimal weight-for-gestation at birth, the higher is the rate of cerebral palsy, the larger is the proportion of male cases, and the more severe is the functional disability. Compared to those with optimum growth the risk of more severe cerebral palsy in male babies is 16 times higher for those with a birth weight below the 3rd centile and four times higher when birth weight is above the 97th centile. In contrast, for mild cerebral palsy in female babies the excess risks at these growth extremes are about half these magnitudes. CONCLUSIONS: Among singleton children with cerebral palsy, abnormal intrauterine size, either small or large, is associated with more severe disability and male sex.

Birth Weight↗
PubMed2005

The effect of dislike of school on risk of teenage pregnancy: testing of hypotheses using longitudinal data from a randomised trial of sex education.

STUDY OBJECTIVE: To examine whether attitude to school is associated with subsequent risk of teenage pregnancy. To test two hypotheses that attitude to school is linked to pregnancy via pathways involving young people having "alternative" expectations or deficits in sexual health knowledge and confidence. DESIGN: Analysis of longitudinal data arising from a trial of sex education. Examination of associations between attitude to school and protected first sex, unprotected first sex, unprotected and protected last sex, and pregnancy, both crude and adjusting in turn for expectation of parenting by age 20, lack of expectation of education/training at age 20, and sexual health knowledge and confidence. SETTING: Schools in central and southern England. PARTICIPANTS: Girls of median age 13.7 years at baseline, 14.7 years at follow up 1, and 16.0 years at follow up 2. MAIN RESULTS: In unadjusted analysis, attitude to school was significantly associated with protected and unprotected first sex by follow up 1, protected first sex between follow up 1 and 2, unprotected last sex, and pregnancy. Dislike of school was more strongly associated with increased risk of these outcomes than was ambivalence to school. These associations remained after adjusting for socioeconomic status and for expectation of parenting, lack of expectation of education/training, and various indicators of knowledge and confidence about sexual health. CONCLUSIONS: Dislike of school is associated with subsequent increased risk of teenage pregnancy but the mechanism underlying any possible causal link is unlikely to involve "alternative" expectations or deficits in sexual health knowledge or confidence.

Adolescent↗