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Biomedical subjects

Andrew Smith

Publications and source records attributed to Andrew Smith.

At least 91 records · Page 5Linked to original sources
PubMed2004

AAV vector delivery to cells in culture.

Adeno-associated virus (AAV) gene delivery vectors are being investigated as vehicles for gene therapy for a wide variety of hereditary and acquired human diseases. AAV's inability to self-propagate, ability to be maintained as an episome in the transduced cell, and relatively innocuous effects on the immune system make it the vector of choice for prolonged in vivo gene expression. AAV type 2 is the most commonly used serotype for gene delivery. AAV2 vectors will deliver DNA to a wide variety of cell types. The development of vectors derived from the other five serotypes has expanded the tissue tropism of the AAV vector system. Tropism depends on the presence of cell-surface receptor elements on the target cell. For AAV2, heparin sulfate proteoglycan (7), alpha2betaV integrin (8) and the fibroblast growth factor receptor-1 (FGFR-1) (9) are believed to mediate the initial internalization steps in infection. The ubiquity of these cell-surface components confers a wide tropism on AAV2 vectors.

Cell Culture Techniques↗
PubMed2004

Surveys of plasma vitellogenin and intersex in male flounder (Platichthys flesus) as measures of endocrine disruption by estrogenic contamination in United Kingdom estuaries: temporal trends, 1996 to 2001.

Plasma vitellogenin (VTG) concentrations and the presence of the ovo-testis (intersex) condition have been recorded in male flounder (Platichthys flesus) captured from several United Kingdom (UK) estuaries since 1996 as part of the endocrine disruption in the Marine Environment (EDMAR) project and earlier programs. It has been confirmed that plasma VTG concentrations in male flounder have remained elevated in several UK estuaries (e.g., Tees, Mersey, and Tyne) throughout the period covered by this study. However, the time-series data indicate that plasma VTG, a measure of environmental estrogen contamination, has decreased in fish captured from several estuaries, especially those of the Tyne and Mersey. Shorter time-series data sets from the Forth and Clyde estuaries also suggest a decrease in estrogen contamination at these sites. Trends associated with specific point sources of estrogenic contamination show site-specific patterns. For instance, plasma VTG levels in male flounder captured near the Howdon sewage treatment outfall (Tyne) have shown a steady decline to near baseline levels in 2001, while the plasma of male fish captured at a site adjacent to the Dabholm Gut discharge in the Tees estuary have shown little evidence of a sustained decline. The occurrence of the intersex condition was detected at a low but consistent prevalence through the study period, with the majority of cases recorded in fish captured from the Tyne and Mersey estuaries. The data set does not allow conclusions to be drawn about any temporal trends associated with this condition. The significance of the findings and possible mitigating influences are discussed in terms of the impacts on wild fish and the role of effluent treatment in reducing these.

Animals↗
PubMed2004

SARS among critical care nurses, Toronto.

To determine factors that predispose or protect healthcare workers from severe acute respiratory syndrome (SARS), we conducted a retrospective cohort study among 43 nurses who worked in two Toronto critical care units with SARS patients. Eight of 32 nurses who entered a SARS patient's room were infected. The probability of SARS infection was 6% per shift worked. Assisting during intubation, suctioning before intubation, and manipulating the oxygen mask were high-risk activities. Consistently wearing a mask (either surgical or particulate respirator type N95) while caring for a SARS patient was protective for the nurses, and consistent use of the N95 mask was more protective than not wearing a mask. Risk was reduced by consistent use of a surgical mask, but not significantly. Risk was lower with consistent use of a N95 mask than with consistent use of a surgical mask. We conclude that activities related to intubation increase SARS risk and use of a mask (particularly a N95 mask) is protective.

Cohort Studies↗
PubMed2004

Physiological and behavioral responses to an exposure of pitch illusion in the simulator.

BACKGROUND: It has been suggested that a pilot's physiological and behavioral responses during disorientation can provide a real-time model of pilot state in order to optimize performance. We investigated whether there were consistent behavioral or physiological "markers" that can be monitored during a single episode of disorientation. METHODS: An Integrated Physiological Trainer with a closed loop interactive aircraft control and point of gaze/eye-tracking device was employed. There were 16 subjects proficient in maintaining straight and level flight and with procedures in changing attitude who were exposed to yaw rotation and a brief head roll to 35 +/- 2 degrees. On return to upright head position, subjects were required to initiate either an ascent or descent to a prescribed attitude. BP, HR, skin conductance, eye movements, and point of gaze were monitored throughout the onset, duration, and immediately after the disorientation insult. Simultaneously, airspeed and power settings were recorded. RESULTS: Compared with the control condition, a significant increase (p < 0.01) in HR, HR variability, and mean arterial BP was observed during the disorientation. Flight performance decrement was reflected by a significant delay in setting power for attitude change and deviation in maintaining airspeed (p < 0.01). CONCLUSION: Changes in cardiovascular responses appear to be correlated with the onset of disorientation. The correlation of changing eye-tracking behavior and flight performance decrement is consistent with our previous findings. Further study is required to determine whether these findings can be extrapolated to repeated exposures and to other disorientation scenarios.

Adult↗
PubMed2003

Biological variation for N-terminal pro- and B-type natriuretic peptides and implications for therapeutic monitoring of patients with congestive heart failure.

Given the limitations of low enrollments, this study suggests that a change of 130% for B-type natiuretic peptide (BNP) and 90% for N-terminal (NT)-proBNP are necessary before results of serially collected data can be considered statistically different. This study also shows that there are important differences in the performance of BNP versus NT-proBNP in monitoring patients with congestive heart failure that need to be further explored.

Adult↗
PubMed2003

Inhibition of LPS-induced splenocyte proliferation by ortho-substituted polychlorinated biphenyl congeners.

Polychlorinated biphenyls (PCBs) are persistent environmental contaminants, and their ubiquitous nature has prompted studies of their potential health hazards. As a result of their lipophilic nature, PCBs accumulate in breast milk and subsequently affect the health of offspring of exposed individuals. Biological effects of PCBs in animals have mostly been attributed to coplanar congeners, although effects of ortho congeners also have been demonstrated. To investigate the relationship of immunotoxicity and chlorine substitution pattern, the effects of PCB congeners and mixtures of ortho and non-ortho-substituted constituents of Aroclor 1242 on splenocytes from C57B1/6 mice were examined. The immunotoxic endpoints investigated included splenocyte viability, lipopolysaccharide (LPS)-induced splenocyte proliferation, and LPS-induced antibody secretion. Congeners with multiple ortho chlorines preferentially inhibited splenocyte proliferation as compared with non- or mono-ortho-substituted congeners. However, mixtures of non- and mono-ortho-substituted congeners and multi-ortho-substituted congeners inhibited LPS-induced splenocyte proliferation and antibody secretion at similar concentrations. Exposure of splenocytes to these mixtures did not activate the aryl hydrocarbon receptor (AhR) signal transduction pathway. These results suggest individual multi-ortho-substituted congeners preferentially inhibit LPS-induced splenocyte proliferation, while congeners not exhibiting an effect individually may have additive effects in a mixture to produce an immunotoxic response through an AhR-independent pathway.

Animals↗
PubMed2003

LFA-1-induced T cell migration on ICAM-1 involves regulation of MLCK-mediated attachment and ROCK-dependent detachment.

This study analyzes signaling events initiated through binding of the leukocyte integrin LFA-1 to ICAM-1, which leads to T cell attachment, polarization and random migration. These events are critically dependent on dynamic changes in the acto-myosin cytoskeleton under the regulation of myosin light chain kinase and ROCK (Rho kinase). A key finding is that the activity of these two kinases is spatially segregated. Myosin light chain kinase (MLCK) must operate at the leading edge of the T cell because blocking its activity causes the polarized T cell to retract from the front of the cell. These activities are mirrored by inhibiting calmodulin, the activator of MLCK. In contrast inhibition of ROCK (and RhoA) has the effect of preventing detachment of the T cell trailing edge, showing that this kinase operates at the rear of the cell. This compartmentalized activity of the two kinases is reflected in their localization within the T cell. Myosin light chain kinase is concentrated at the leading edge, overlapping F-actin, whereas ROCK is more widely distributed in the trailing edge of the T cell. Thus these two kinases perform two different functions in the migrating T cell, with myosin light chain kinase activity important for attachment and movement at the leading edge and ROCK activity required for the detachment of the trailing edge. These two actomyosin-dependent processes operate coordinately to cause forward migration of a T cell.

Cell Adhesion↗
PubMed2003

NAD+-dependent DNA ligases of Mycobacterium tuberculosis and Streptomyces coelicolor.

Sequencing of the genomes of Mycobacterium tuberculosis H37Rv and Streptomyces coelicolor A3(2) identified putative genes for an NAD(+)-dependent DNA ligase. We have cloned both open reading frames and overexpressed the protein products in Escherichia coli. In vitro biochemical assays confirm that each of these proteins encodes a functional DNA ligase that uses NAD(+) as its cofactor. Expression of either protein is able to complement E. coli GR501, which carries a temperature-sensitive mutation in ligA. Thus, in vitro and in vivo analyses confirm predictions that ligA genes from M. tuberculosis and S. coelicolor are NAD(+)-dependent DNA ligases.

Amino Acid Sequence↗
PubMed2003

SKAP-55 regulates integrin adhesion and formation of T cell-APC conjugates.

Src kinase-associated phosphoprotein of 55 kDa (SKAP-55; encoded by SCAP1) is a T cell adaptor protein of unknown function that contains a pleckstrin homology and an SH3 domain. Here we show that SKAP-55 regulates integrin-mediated adhesion and conjugate formation between T cells and antigen-presenting cells (APCs). SKAP-55 enhances adhesion to fibronectin and intercellular adhesion molecule-1 (ICAM-1), colocalizes with actin at the T cell-APC synapse and promotes the clustering of lymphocyte-associated antigen-1 (LFA-1). Enhanced conjugation is comparable to that induced by adhesion and degranulation-promoting adaptor protein (ADAP), a binding partner of SKAP-55, and is abrogated by deletion of the SKAP-55 SH3 domain. Conjugate formation is accompanied by the translocation of SKAP-55 to membrane rafts, an event that is regulated by both LFA-1 and T cell receptor ligation. Our findings identify a mechanism by which SKAP-55 modulates T cell responses to antigen.

Animals↗
PubMed2003

Passing on tacit knowledge in anaesthesia: a qualitative study.

OBJECTIVE: To explore the acquisition of knowledge in anaesthetic practice using qualitative methods. METHODS: An ethnographic study examining the nature of expertise in anaesthesia in one English hospital. The study used qualitative research methods, including observation of anaesthetic practice and interviews with members of the anaesthetic team. An integral part of the study was a process of feedback to the anaesthetic team including presenting observational data and conducting debriefing interviews with individual team members. RESULTS: The study highlights the continued importance of the clinical apprenticeship in passing on knowledge, but also emphasizes the central role of practising independently in the acquisition of skills. Anaesthetists who participated in debriefing interviews or read observational transcripts found the experience valuable for thinking about their own practice. DISCUSSION: One suggestion arising from the use of qualitative methods in this setting is that the type of detailed, systematic observation and data recording used in this study could be beneficial in the training and, possibly, appraisal of anaesthetists. This novel and innovative application of qualitative methods in anaesthesia is described and discussed with a view to broadening the debate about specialist training.

Anesthesia↗
PubMed2003

Oral focal mucinosis: report of 15 cases and review of the literature.

AIMS: To describe 15 cases of oral focal mucinosis (OFM) and compare these to previously reported cases. METHODS: Cases diagnosed as OFM in the period 1981-2003-were reviewed. Clinical information provided at the time of submission of each specimen was retrieved and supplemented by additional clinical details provided by the respective clinician at the time of compilation of this paper. The literature was reviewed. RESULTS: OFM presented as an innocuous soft tissue swelling that may be either pedunculated or sessile. The gingiva was confirmed as the most common site for OFM, with a predominance of females affected. Microscopically, OFM is characterised by an area of myxoid tissue which is usually well-defined. The lesion is periodic acid-Schiff (PAS)-negative and alcian blue-positive, with pre-digestion with hyaluronidase preventing the alcian blue staining. As the differential diagnosis includes myxoid neural lesions, S100 staining is important in establishing the diagnosis, with cases of OFM being negative. CONCLUSIONS: The cause of OFM remains unknown. The cases presented in this paper bring OFM to the attention of anatomical pathologists when considering the differential diagnosis of myxoid lesions of the oral cavity.

Adolescent↗
PubMed2003

A transition probability model for amino acid substitutions from blocks.

Substitution matrices have been useful for sequence alignment and protein sequence comparisons. The BLOSUM series of matrices, which had been derived from a database of alignments of protein blocks, improved the accuracy of alignments previously obtained from the PAM-type matrices estimated from only closely related sequences. Although BLOSUM matrices are scoring matrices now widely used for protein sequence alignments, they do not describe an evolutionary model. BLOSUM matrices do not permit the estimation of the actual number of amino acid substitutions between sequences by correcting for multiple hits. The method presented here uses the Blocks database of protein alignments, along with the additivity of evolutionary distances, to approximate the amino acid substitution probabilities as a function of actual evolutionary distance. The PMB (Probability Matrix from Blocks) defines a new evolutionary model for protein evolution that can be used for evolutionary analyses of protein sequences. Our model is directly derived from, and thus compatible with, the BLOSUM matrices. The model has the additional advantage of being easily implemented.

Amino Acid Substitution↗
PubMed2003

Alternative venous outflow vessels in microvascular breast reconstruction.

The lack of adequate recipient vessels often complicates microvascular breast reconstruction in patients who have previously undergone mastectomy and irradiation. In addition, significant size mismatch, particularly in the outflow veins, is an important contributor to vessel thrombosis and flap failure. The purpose of this study was to review the authors' experience with alternative venous outflow vessels for microvascular breast reconstruction. In a retrospective analysis of 1278 microvascular breast reconstructions performed over a 10-year period, the authors identified all patients in whom the external jugular or cephalic veins were used as the outflow vessels. Patient demographics, flap choice, the reasons for the use of alternative venous drainage vessels, and the incidence of microsurgical complications were analyzed. The external jugular was used in 23 flaps performed in procedures with 22 patients. The superior gluteal and transverse rectus abdominis musculocutaneous (TRAM) flaps were used in the majority of the cases in which the external jugular vein was used (72 percent gluteal, 20 percent TRAM flap). The need for alternative venous outflow vessels was usually due to a significant vessel size mismatch between the superior gluteal and internal mammary veins (74 percent). For three of the external jugular vein flaps (13 percent), the vein was used for salvage after the primary draining vein thrombosed, and two of three flaps in these cases were eventually salvaged. In three patients, the external jugular vein thrombosed, resulting in two flap losses, while the third was salvaged using the cephalic vein. A total of two flaps were lost in the external jugular vein group. The cephalic vein was used in 11 flaps (TRAM, 64.3 percent; superior gluteal, 35.7 percent) performed in 11 patients. In five patients (54.5 percent), the cephalic vein was used to salvage a flap after the primary draining vein thrombosed; the procedure was successful in four cases. In three patients, the cephalic vein thrombosed, resulting in two flap losses. One patient suffered a thrombosis after the cephalic vein was used to salvage a flap in which the external jugular vein was initially used, leading to flap loss, while a second patient experienced cephalic vein thrombosis on postoperative day 7 while carrying a heavy package. There was only one minor complication attributable to the harvest of the external jugular or cephalic vein (small neck hematoma that was aspirated), and the resultant scars were excellent. The external jugular and cephalic veins are important ancillary veins available for microvascular breast reconstruction. The dissection of these vessels is straightforward, and their use is well tolerated and highly successful.

Anastomosis, Surgical↗
PubMed2003

Improving recipient vessel exposure during microvascular breast reconstruction.

Microvascular tissue transfer has become the gold standard for breast reconstruction. The primary drawback to these procedures is the technical expertise required for microsurgical anastomosis. This problem is compounded by the difficulties in the exposure of recipient vessels deep within the axilla. Previous techniques used for exposure of these vessels are difficult to setup, provide less than optimal exposure, and have been associated with brachial plexus injuries. The authors retrospectively review their experience using the pediatric OMNI retractor for exposure of recipient vessels during microvascular breast reconstruction. Patient demographics, flap choice, recipient vessels, the incidence of neuropraxia/brachial plexopathy, and microvascular complications were analyzed. Patients in whom more traditional methods of vessel exposure were used (ie, Gelpi retractors, arm positioning, fish hooks; 517 reconstructions in 392 patients) were compared with patients in whom vessel exposure was performed using the pediatric OMNI retractor (699 reconstructions in 571 patients). No differences were noted in comorbid conditions or the incidence of microvascular complications. However, the use of the pediatric OMNI was associated with a significant reduction in operative time in unilateral reconstructions (6:23 +/- 0.05 h vs 7:48 +/- 0.05 h; P <0.01) and decreased incidence of brachial plexus injury (0.17% vs 3.3%; P <0.01). The authors think the decreased neuropraxia rate is the result of better exposure afforded by the pediatric OMNI retractor, which improves exposure and eliminates the need for excessive arm abduction or awkward positioning during the dissection and anastomosis of axillary recipient vessels.

Adolescent↗