Search PubMed⌕ Search

Biomedical subjects

S Sawyer

Publications and source records attributed to S Sawyer.

At least 19 recordsLinked to original sources
PubMed2003

Molecular diversity of RNA-2 genome segments in pecluviruses causing peanut clump disease in West Africa and India.

The complete nucleotide sequence of RNA-2 genome segments of four isolates of Peanut clump virus (PCV) and two isolates of Indian peanut clump virus (IPCV) were determined. Comparisons among the complete RNA-2 sequences of six isolates from this study and two published earlier, revealed a high degree of variability in size (between 4290 and 4652 nucleotides) and nucleotide sequence identities (between 58 % and 79 %). Amino acid sequence alignments of the five open reading frames (ORF) showed that ORF 4, which encodes the second of the triple gene block proteins, is highly conserved (90 to 98 % identical) whereas the protein encoded by ORF 2, whose function is unknown, is less conserved (25 to 60 % identical). The coat protein of the eight isolates showed amino acid identities between 37 % and 89 % and contained several conserved residues. Phylogenetic comparisons, based on complete RNA-2 sequences, revealed that the eight isolates grouped into two distinct clusters with no geographical distinction between PCV and IPCV isolates. Phylogenetic tree topologies for individual ORFs showed an overall similarity with that obtained from entire RNA-2 sequences, although the relative positions of individual isolates vary within each cluster. The results indicate that there is substantial divergence among the RNA-2 genomes of pecluviruses and suggest that different proteins have evolved differently, possibly due to different selection pressures.

Africa, Western↗
PubMed2003

General anaesthesia or conscious sedation for painful procedures in childhood cancer: the family's perspective.

BACKGROUND: Until recently, midazolam sedation was routinely used in our institution for bone marrow aspirates and lumbar punctures in children with cancer. It has been perceived by many doctors and nurses as being well tolerated by children and their families. AIM: To compare the efficacy of inhalational general anaesthesia and midazolam sedation for these procedures. METHODS: A total of 96 children with neoplastic disorders, who received either inhalational general anaesthesia with sevoflurane, nitrous oxide, and oxygen (GA) or sedation with oral or nasal midazolam (SED) as part of their routine preparation for procedures were studied. The experiences of these children were examined during their current procedure and during their first ever procedure. Main outcome measures were the degree of physical restraint used on the child, and the levels of distress and pain experienced by the child during the current procedure and during the first procedure. The family's preference for future procedures was also determined. RESULTS: During 102 procedures under GA, restraint was needed on four occasions (4%) when the anaesthetic mask was first applied, minimal pain was reported, and children were reported as distressed about 25% of the time. During 80 SED procedures, restraint was required in 94%, firm restraint was required in 66%, the child could not be restrained in 14%, median pain score was 6 (scale 0 (no pain) to 6 (maximum pain)), and 90% of the parents reported distress in their child. Ninety per cent of families wanted GA for future procedures. Many families reported dissatisfaction with the sedation regime and raised concerns about the restraint used on their child. CONCLUSIONS: This general anaesthetic regime minimised the need for restraint and was associated with low levels of pain and distress. The sedation regime, by contrast, was much less effective. There was a significant disparity between the perceptions of health professionals and those of families with respect to how children coped with painful procedures.

Adolescent↗
PubMed2001

Directional selection and the site-frequency spectrum.

In this article we explore statistical properties of the maximum-likelihood estimates (MLEs) of the selection and mutation parameters in a Poisson random field population genetics model of directional selection at DNA sites. We derive the asymptotic variances and covariance of the MLEs and explore the power of the likelihood ratio tests (LRT) of neutrality for varying levels of mutation and selection as well as the robustness of the LRT to deviations from the assumption of free recombination among sites. We also discuss the coverage of confidence intervals on the basis of two standard-likelihood methods. We find that the LRT has high power to detect deviations from neutrality and that the maximum-likelihood estimation performs very well when the ancestral states of all mutations in the sample are known. When the ancestral states are not known, the test has high power to detect deviations from neutrality for negative selection but not for positive selection. We also find that the LRT is not robust to deviations from the assumption of independence among sites.

Alleles↗
PubMed2000

Mcm10 and the MCM2-7 complex interact to initiate DNA synthesis and to release replication factors from origins.

MCM2-7, a complex of six subunits, is an essential component of the prereplication chromatin that is assembled at Saccharomyces cerevisiae replication origins during G(1) phase. It is also believed to be the processive helicase at growing forks. To elucidate the action of MCM2-7 during the transition from initiation to elongation replication, we have focused our studies on Mcm10, a replication initiation protein that physically interacts with members of the MCM2-7 complex. We show that Mcm10 is a chromatin-associated protein that mediates the association of the MCM2-7 complex with replication origins. Furthermore, diminished interaction between Mcm10 and Mcm7, a subunit of the MCM2-7 complex, by a mutation in either Mcm10 or Mcm7 inhibits replication initiation. Surprisingly, a double mutant containing both the mcm10-1 and mcm7-1 (cdc47-1) alleles restores interaction between Mcm10 and Mcm7 and corrects all of the defects exhibited by each of the single mutants, including the stalling of replication forks at replication origins typically seen in mcm10-1 cells. This mutual compensation of defects between two independently isolated mutations is allele specific. These results suggest that Mcm10, like Mcm7, is a critical component of the prereplication chromatin and that interaction between Mcm10 and Mcm7 is required for proper replication initiation and prompt release of origin-bound factors.

Alleles↗
PubMed2000

Attentional function in secondary school students receiving isoniazid prophylaxis for tuberculosis infection.

Reports have suggested that isoniazid treatment may be associated with poor concentration and subtle reduction in memory. This study examines attentional function and processing speed in a group of 25 adolescents who received isoniazid prophylaxis for at least 6 months. As adolescents often face major educational assessment milestones, such cognitive side effects may have important implications. Participants were assessed before treatment, 1 month into treatment and at least 1 week after treatment cessation. Measures included the Paced Auditory Serial Addition Test and subtests of the appropriate Wechsler scale sensitive to attention and speed of information processing. Isoniazid does not appear to cause significant adverse effects on attentional function in adolescents.

Adolescent↗
PubMed2000

Evaluation of an automated system for the collection of packed RBCs, platelets, and plasma.

BACKGROUND: This study evaluated the quality of WBC-reduced platelets, RBCs, and plasma collected on a new system (Trima, Gambro BCT) designed to automate the collection of all blood components. The study also evaluated donor safety and suitability of these components for transfusion. STUDY DESIGN AND METHODS: In Phase I, the quality of the components collected on the new system was evaluated by standard in vitro and in vivo testing methods. Results were compared to those from control components collected by currently approved standard methods. In Phase II, additional collections were performed to evaluate the acceptability of the new system and the safety of platelets collected. RESULTS: In vivo 24-hour RBC recovery was 76.8 +/- 3.1 percent for the test RBC units and 77.1 +/- 4.4 percent recovery for whole-blood (control) RBCs. The differences between test and control platelet results in the in vivo and in vitro assays were not clinically significant. Plasma clotting factors and fibrinogen levels met international standards. The system was well accepted by donors, and no major adverse donor reactions were reported for the 68 procedures performed. No problems were reported with transfusing the blood components collected. CONCLUSION: Blood components collected with the Trima are equivalent to currently available components, and they meet the applicable regulatory standards. This system provides consistent, standardized components with predictable yields. It provides the option of fully automating the collection of all blood components.

Adult↗
PubMed2000

Obesity in childhood and adolescence.

BACKGROUND: Obesity in childhood and adolescence is increasing in developed countries around the world. Management is often difficult and can be unsuccessful. OBJECTIVE: The epidemiology, causes and complications of obesity in childhood and adolescence are described, and a general clinical approach to weight management is provided. DISCUSSION: In general, a comprehensive history and examination can elicit medical causes of obesity. This paper does not seek to expand on medical causes but rather focuses on the clinical issues dealing with management of the overweight child or adolescent. This approach relies on actively engaging the child or young person, as well as involving the entire family in the process. Weight management consists of a combination of healthy eating behaviour and engaging in physical activity.

Adolescent↗
PubMed1999

Possible emergence of new geminiviruses by frequent recombination.

Although exchange of genetic information by recombination plays a role in the evolution of viruses, the extent to which it generates diversity is not clear. We analyzed genomes of geminiviruses for recombination using a new statistical procedure developed to detect gene conversions. Geminiviruses (family, Geminiviridae) are a group of plant viruses characterized by a genome of circular single-stranded DNA (approximately 2700 nucleotides in length) encapsidated in twinned quasi-isometric particles. Complete nucleotide sequences of geminiviruses were aligned, and recombination events were detected by searching pairs of viruses for sequences that are significantly more similar than expected based on random distribution of polymorphic sites. The analyses revealed that recombination is very frequent and occurs between species and within and across genera. Tests identified 420 statistically significant recombinant fragments distributed across the genome. The results suggest that recombination is a significant contributor to geminivirus evolution. The high rate of recombination may be contributing to the recent emergence of new geminivirus diseases.

Evolution, Molecular↗
PubMed1999

Quality and clinical response to transfusion of prestorage white cell-reduced apheresis platelets prepared by use of an in-line white cell-reduction system.

BACKGROUND: This study evaluated the quality and clinical effectiveness of white cell (WBC)-reduced apheresis platelets collected by the use of a new technology, fluidized particle-bed separation. STUDY DESIGN AND METHODS: In phase 1, six suitable donors underwent two separate plateletpheresis procedures on one occasion, each separated by less than 10 minutes. In random order, a control unit was collected with the COBE Spectra and a test unit with the Spectra Leukocyte-Reduction System (LRS). The quality of apheresis platelet components was assessed by an in vitro test panel, and residual WBCs were counted by Nageotte chamber and flow cytometric methods. For the in vivo studies, the test and control units were randomly labeled with either 51Cr or 111In at the end of storage and transfused simultaneously to the donor. Samples were taken for calculation of platelet survival and recovery. In phase II, 109 thrombocytopenic patients were given platelets collected by use of the Spectra LRS. RESULTS: Test platelets had significantly fewer residual WBCs (median 7.6 x 10(4)) than control platelets (median 3.9 x 10(5)), with equivalent in vitro function values. Test and control platelets had similar recovery and survival. Transfused platelets collected by use of the LRS achieved a mean 1-hour corrected-count increment of 19.3. CONCLUSION: The LRS collects platelet components with significantly lower WBC contamination without adverse effects on the function or in vivo survival of the platelets.

Blood Platelets↗
PubMed1999

A novel approach to monitoring adherence to preventive therapy for tuberculosis in adolescence.

OBJECTIVES: To evaluate the usefulness of a microelectronic tablet-dispenser for monitoring adherence to preventive therapy for tuberculosis infection in adolescents. METHODOLOGY: Twenty-one patients with positive Mantoux tests were treated with isoniazid (INH), dispensed in a microelectronic tablet-dispenser that recorded the date, time and duration that the container was opened. Other measures of adherence included attendance at clinic, patient self-report, tablet count, and measurement of urinary INH metabolites. RESULTS: The mean adherence rates were: 83% using attendance at clinic, 91% using tablet counts, 79% using urine assays, and 66% using the electronic tablet-dispenser. Self-reporting appeared to over-estimate adherence. CONCLUSION: Adherence to 6 months of INH calculated using different measures is higher in this study than in previous reports. Microelectronic tablet-dispensers are an effective method to objectively measure adherence on a daily basis. Other measures are less helpful.

Adolescent↗
PubMed1998

Arterial heparin deposition: role of diffusion, convection, and extravascular space.

Transvascular transport has been studied with atherogenic, tracer, and inert compounds such as low-density lipoprotein, horseradish peroxidase, and albumin, respectively. Few studies used vasoactive compounds, and virtually all studies examined entry from the lumen and not from the perivascular space. We compared several mechanisms that govern arterial heparin deposition after administration to the perivascular and endovascular aspects of the calf carotid artery in vitro and the rabbit iliac artery in vivo. In the absence of transmural hydrostatic pressure gradients, heparin deposition following endovascular administration was unaffected by deendothelialization and was indistinguishable from perivascular delivery. Deposition in the former was enhanced by the addition of a pressure gradient and to a greater extent in denuded arteries, indicating that convection influences transport but is dampened by the endothelium. Neither the endothelium nor the adventitia pose significant resistances to heparin. Deposition in vivo was greater following endovascular hydrogel release than perivascular application from similar devices to native or denuded arteries. The loss of drug to extra-arterial microvessels exceeded the loss of drug to the lumen flow. These findings are essential for describing vascular pharmacokinetics and for implementing local pharmacotherapies.

Animals↗
PubMed1998

Smoking prevention and cessation in adolescents.

Tobacco smoking is the most important preventable health risk factor in Australia. It has lost popularity and acceptability in Australia as a result of public health campaigns and their reinforcement through government legislation. The rate of smoking in Australia has gradually declined due to increased cessation in adults. Adolescents, however, are smoking as much as ever. The aim of this paper is to provide family practitioners with practical, simple clinical strategies to reduce teenage smoking.

Adolescent↗
PubMed1997

Interferon-gamma protects against herpes simplex virus type 1-mediated neuronal death.

Host inflammatory mediators, such as interferons, play a protective role in infection, but the mechanism is undefined and may differ between tissue compartments. To determine whether interferon-gamma (IFN-gamma) elicitation prevents destructive encephalitis in herpes simplex virus type 1 (HSV-1) infection of the central nervous system, IFN-gamma-knockout (GKO) mice were challenged intravitreally with HSV-1 strain F, inciting infection of the eyes and the brain. Indeed, the GKO mice showed encephalitis with ataxia, whereas nontransgenic controls remained asymptomatic. Morphology and digoxigenin labeling of DNA fragments revealed increased apoptosis in the brains of GKO mice compared with controls, although viral replication was not influenced at early stages of infection. Greater numbers of apoptotic cells in the brains of GKO mice correlated with neurological symptoms, as well as lower expression of the protective protooncogene bcl-2. Thus, IFN-gamma inhibits apoptosis, affording neuronal protection from destructive encephalitis during viral infection of the central nervous system.

Animals↗
PubMed1997

Effects of short and long term ethanol on the activation of signal transducer and activator transcription factor 3 in normal and regenerating liver.

Interleukin-6 (IL-6) induced activation of Signal Transducer and Activator Transcription Factor 3 (Stat3) is a critical step in liver regeneration. Chronic ethanol consumption is known to increase the plasma concentration of IL-6, yet the ability of the liver to regenerate and the regenerative induction of several IL-6 initiated events are impaired in chronic alcoholic liver disease. We hypothesized that chronic ethanol consumption inhibits IL-6 dependent signal transduction. To test this hypothesis, the effect of ethanol on the Stat3 signal transduction pathway was studied in the adult rat liver. In vitro treatment of freshly isolated normal adult rat hepatocytes with 50-100 mM ethanol for 30 min blocked IL-6-induced Stat3 activation. Long-term ethanol intake in vivo significantly attenuated the activation of Stat3 induced either in vivo by partial hepatectomy or in vitro by IL-6. In contrast, short-term ethanol consumption enhanced the regenerative induction of Stat3 but inhibited IL-6 induced Stat3 activation. These data suggest that the inhibition of liver regeneration by chronic ethanol consumption is, at least in part, mediated by modulating the activation of Stat3.

Administration, Oral↗
PubMed1997

Studies on platelets exposed to or stored at temperatures below 20 degrees C or above 24 degrees C.

BACKGROUND: Platelet concentrates (PCs) may be subjected to temperatures outside 20 to 22 degrees C during shipping or storage, which may have an adverse effect on platelet quality. STUDY DESIGN AND METHODS: These studies systematically evaluated the effect of short-term exposure (< or = 24 hours) of platelets to temperatures above 22 degrees or below 20 degrees C as part of standard 5-day PC storage at 22 degrees C, as well as the effect of long-term storage (5 days) at 24 and 26 degrees C. For the short-term exposure studies, up to 6 units of Day 1 standard PCs were mixed, split, and returned to the containers. Test units were then stored without agitation in an incubator at a specific temperature (4, 12, 16, or 18 degrees C) for various times up to 24 hours, after which they were stored with agitation at 22 degrees C. One unit acted as control and was stored at 20 to 22 degrees C throughout the 5-day storage period. Loss of platelet discoid shape was determined photometrically by the extent of shape change assay, by an increase in apparent platelet size by morphologic evaluation, and by swirling. RESULTS: A gradual loss of platelet discoid shape occurred at temperatures below 20 degrees C. For similar periods, a greater difference between test and control PCs was observed in units held at 4 degrees C than in those held at 16 degrees C. The data were fitted to an equation to relate platelet discoid shape (% of control) to exposure temperature and time. Assuming that a 20-percent decrease or more in the extent of shape change assay represents a significant loss in platelet viability, the equation predicts that such a loss occurs when the platelets are exposed to 16 degrees C for > or = 16 hours, to 12 degrees C for > or = 10 hours, or to 4 degrees C for > or = 6 hours, whereas exposure to 18 degrees C for < or = 24 hours has no significant effect. Storage for 5 days at temperatures < or = 26 degrees C was not associated with any significant reduction in platelet discoid shape or other measures of platelet quality. CONCLUSION: There was a gradual loss of platelet discoid shape at exposure temperatures < 20 degrees C, which worsened as temperatures decreased and exposure times increased to 24 hours. This relationship can be described in an equation that could be used as a guideline for allowable exposure conditions.

Blood Platelets↗