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Biomedical subjects

K W Dunn

Publications and source records attributed to K W Dunn.

At least 19 recordsLinked to original sources
PubMed2006

Digitisation of the total burn surface area.

The assessment of surface area of the body affected by a burn (TBSA) has long been estimated with manual charts. Initial assessment of burned patients is made frequently by clinicians with limited experience producing significant errors. Paper copies of burn charts are unwieldy, subject to loss and tend towards overestimation. Thus, a simple method of calculation, recording and transmission via email or telemedicine may produce benefits in both initial treatment and data recording. Although computer-based systems have been reported previously none have entered routine clinical practice in the UK. We devised a PC-based program, "Burn Calculator", whereby digital transcription of the burn allows automatic area calculation allowing not only a rapid, accurate figure for determination of fluid resuscitation, but also the potential for rapid electronic transmission. It also calculates fluid requirements to minimise errors during resuscitation. This initial pilot study compared figures from 50 paper charts with those from Burn Calculator to determine its accuracy and reproducibility. Previously reported variations in TBSA estimation were confirmed, as was the tendency towards TBSA underestimation resulting from transcription of a three-dimensional clinical situation to a two-dimensional representation. Burn Calculator showed high correlation (r=0.9850; p<0.0001) and reproducibility (R=0.9957) that would simplify assessment and referral plus facilitate data collection, interpretation and research.

Adolescent↗
PubMed2005

Performance comparison between the high-speed Yokogawa spinning disc confocal system and single-point scanning confocal systems.

Fluorescence microscopy of the dynamics of living cells presents a special challenge to a microscope imaging system, simultaneously requiring both high spatial resolution and high temporal resolution, but with illumination levels low enough to prevent fluorophore damage and cytotoxicity. We have compared the high-speed Yokogawa CSU10 spinning disc confocal system with several conventional single-point scanning confocal (SPSC) microscopes, using the relationship between image signal-to-noise ratio and fluorophore photobleaching as an index of system efficiency. These studies demonstrate that the efficiency of the CSU10 consistently exceeds that of the SPSC systems. The high efficiency of the CSU10 means that quality images can be collected with much lower levels of illumination; the CSU10 was capable of achieving the maximum signal-to-noise of an SPSC system at illumination levels that incur only at 1/15th of the rate of the photobleaching of the SPSC system. Although some of the relative efficiency of the CSU10 system may be attributed to the use of a CCD rather than a photomultiplier detector system, our analyses indicate that high-speed imaging with the SPSC system is limited by fluorescence saturation at the high levels of illumination frequently needed to collect images at high frame rates. The high speed, high efficiency and freedom from fluorescence saturation combine to make the CSU10 effective for extended imaging of living cells at rates capable of capturing the three-dimensional motion of endosomes moving up to several micrometres per second.

Animals↗
PubMed2005

Informed consent should be obtained from patients to use products (skin substitutes) and dressings containing biological material.

BACKGROUND: Biological products (tissue engineered skin, allograft and xenograft, and biological dressings) are widely used in the treatment of burns, chronic wounds, and other forms of acute injury. However, the religious and ethical issues, including consent, arising from their use have never been addressed in the medical literature. AIMS: This study was aimed to ascertain the views of religious leaders about the acceptability of biological products and to evaluate awareness among healthcare professionals about their constituents. METHODS: The religious groups that make up about 75% of the United Kingdom population were identified and a questionnaire on 11 biological products was sent to its leaders. Another questionnaire concerning 17 products (11 biological and 6 synthetic dressings) was sent to 100 healthcare professionals working in seven specialist units in the UK. RESULTS: All religious leaders (100% response rate) replied, some after consultation with international bodies. Among them, 77% said that patients should be informed of the constituents of the biological products and consent obtained. Some leaders expressed concerns about particular products including the transmission of viral and prion diseases, cruelty to animals, and material derived from neonates. None of the healthcare professionals (73% response rate) surveyed knew the constituents of all the products correctly. CONCLUSION: Ignoring religious sensitivities and neglecting consent in the usage of biological products could have very serious implications, including litigation. Hospitals and manufacturers should take immediate measures to enlighten healthcare professionals of the constituents of these products so that they can obtain informed consent from patients.

Attitude to Health↗
PubMed2003

An investigation of the suitability of bra fit in women referred for reduction mammaplasty.

Reduction mammaplasty is rationed in NHS plastic surgery provision, despite abundant evidence that most women who undergo this operation obtain significant improvement in their physical health and quality of life. We suspected that women seeking reduction mammaplasty often wear ill-fitting bras, which may exacerbate some of their symptoms. Therefore, we studied 103 women who attended a nurse-run pre-assessment clinic, asking them what size bra they currently wore and then measuring them to see whether their bra size was correct. We also questioned bra manufacturers, designers and shop bra fitters about bra manufacture, sizing and fitting techniques, and we reviewed these findings. Of the 102 women suitable for inclusion in the study, all wore the wrong size bra. Their mean 'claimed' back measurement was 36 inches (range: 30-42 in.) and their mean cup size was F (range: C-J). We found that all but one underestimated their back measurement (by a mean of 4 in.; range: -2-10 in.) and overestimated their cup size (by a mean of three sizes; range: one size smaller to seven sizes larger) when compared with manufacturers' fitting guidelines. Multiple regression analysis used to assess the relationships of various factors to incorrect bra sizing showed a strong link (Pearson correlation=0.54; P<0.001) between obesity and inaccurate back measurement. The reasons why women with breast hypertrophy wear incorrectly fitting bras are discussed. We conclude that obesity, breast hypertrophy, fashion and bra-fitting practices combine to make those women who most need supportive bras the least likely to get accurately fitted bras, so exacerbating the symptoms for which they seek surgery.

Adolescent↗
PubMed2003

Implications for Burns Unit design following outbreak of multi-resistant Acinetobacter infection in ICU and Burns Unit.

We reviewed the emergence of 13 cases of multi-resistant Acinetobacter infection in burns patients over a 12-month period. The outbreak was started in a non-burn patient in the intensive care unit (ICU) that spread to burns patients in ICU and then the Burns Unit. The importance of opportunistic infection, potential risk factors, treatment and clinical outcome of Acinetobacter infection in burns patients from this cluster of cases is described. This paper implicates the movement of burns patients and medical equipment between ICU and the Burns Unit in the spread of this infection. Future design of Burn Units should aim to incorporate features to allow the management of all burns cases in one location with all intensive care, burns and theatre facilities built in close proximity.

Acinetobacter Infections↗
PubMed2001

Three-dimensional imaging of embryonic mouse kidney by two-photon microscopy.

Developing mammalian embryonic kidney becomes progressively more elaborate as the ureteric bud branches into undifferentiated mesenchyme. Morphological perturbations of nephrogenesis, such as those seen in inherited renal diseases or induced in transgenic animals, require careful and often tedious documentation by multiple methodologies. We have applied a relatively quick and simple approach combining two-photon microscopy and advanced three-dimensional (3-D) imaging techniques to visualize and evaluate these complex events. As compared with laser confocal microscopy, two-photon microscopy offers superior optical sectioning deep into biological tissues, permitting analysis of large, heterogeneous, 3-D structures such as developing mouse kidney. Embryonic and newborn mouse kidneys were fluorescently labeled with lectins, phalloidin, or antibody. Three-dimensional image volumes were then collected. The resulting volume data sets were processed using a novel 3-D visualization technique. Reconstructed image volumes demonstrate the dichotomous branching of ureteric bud as it progresses from a simple, symmetrical structure into an elaborate, asymmetrical collecting system of multiple branches. Detailed morphology of in situ cysts was elucidated in a transgene-induced mouse model of polycystic kidney disease. We expect this integration of two-photon microscopy with advanced 3-D image analysis will provide a powerful tool for illuminating a variety of complex developmental processes in multiple dimensions.

Animals↗
PubMed2001

The acute febrile response to burn injury in children may be modified by the type of intravenous fluid used during resuscitation--observations using fresh frozen plasma (FFP) or Hartmann's solution.

Fever is a common clinical problem in burned children. The purpose of this study was to compare rectal temperature (T(r)) in two groups of children with burns, > or =10% of the total body surface area (tbsa) who received fresh frozen plasma (FFP) or a crystalloid solution (Hartmann's) for restoration of blood volume. Twelve to 16 h after the burn T(r) reached a peak. The children who had received FFP for restoration of blood volume had significantly higher fever than those children who received crystalloid solutions only.

Acute Disease↗
PubMed2001

Brefeldin A rapidly disrupts plasma membrane polarity by blocking polar sorting in common endosomes of MDCK cells.

Recent studies showing thorough intermixing of apical and basolateral endosomes have demonstrated that endocytic sorting is critical to maintaining the plasma membrane polarity of epithelial cells. Our studies of living, polarized cells show that disrupting endocytosis with brefeldin-A rapidly destroys the polarity of transferrin receptors in MDCK cells while having no effect on tight junctions. Brefeldin-A treatment induces tubulation of endosomes, but the sequential compartments and transport steps of the transcytotic pathway remain intact. Transferrin is sorted from LDL, but is then missorted from common endosomes to the apical recycling endosome, as identified by its nearly neutral pH, and association with GFP chimeras of Rabs 11a and 25. From the apical recycling endosome, transferrin is then directed to the apical plasma membrane. These data are consistent with a model in which polarized sorting of basolateral membrane proteins occurs via a brefeldin-A-sensitive process of segregation into basolateral recycling vesicles. Although disruption of polar sorting correlates with dissociation of gamma-adaptin from endosomes, gamma-adaptin does not appear to be specifically involved in sorting into recycling vesicles, as we find it associated with the transcytotic pathway, and particularly to the post-sorting transcytotic apical recycling endosome.

Adaptor Protein Complex gamma Subunits↗
PubMed2000

Lysosomal accumulation of drugs in drug-sensitive MES-SA but not multidrug-resistant MES-SA/Dx5 uterine sarcoma cells.

Sequestration of drugs in intracellular vesicles has been associated with multidrug-resistance (MDR), but it is not clear why vesicular drug accumulation, which depends upon intracellular pH gradients, should be associated with MDR. Using a human uterine sarcoma cell line (MES-SA) and a doxorubicin (DOX)-resistant variant cell line (Dx-5), which expresses p-glycoprotein (PGP), we have addressed the relationship between multidrug resistance, vesicular acidification, and vesicular drug accumulation. Consistent with a pH-dependent mechanism of vesicular drug accumulation, studies of living cells vitally labeled with multiple probes indicate that DOX and daunorubicin (DNR) predominately accumulate in lysosomes, whose lumenal pH was measured at < 4.5, but are not detected in endosomes, whose pH was measured at 5.9. However, vesicular DOX accumulation is more pronounced in the drug-sensitive MES-SA cells and minimal in Dx5 cells even when cellular levels of DOX are increased by verapamil treatment. While lysosomal accumulation of DOX correlated well with pharmacologically induced differences in lysosome pH in MES-SA cells, lysosomal accumulation was minimal in Dx5 cells regardless of lysosomal pH. We found no differences in the pH of either endosomes or lysosomes between MES-SA and Dx5 cells, suggesting that, in contrast to other MDR cell systems, the drug-resistant Dx5 cells are refractory to pH-dependent vesicular drug accumulation. These studies demonstrate that altered endomembrane pH regulation is not a necessary consequence of cell transformation, and that vesicular sequestration of drugs is not a necessary characteristic of MDR.

Animals↗
PubMed2000

Experience with severe extensive blistering skin disease in a paediatric burns unit.

Vesiculobullous disorders are thankfully uncommon. A brief overview of the literature is presented together with our experience of managing these cases on a paediatric burns unit in the six years 1992 1998. The advantages of management on such a unit are outlined and include a facility for major dressings and frequent changes and a familiarity with fluid resuscitation in the child with major skin loss. The financial cost of treatment and rehabilitation of these children is high.

Burn Units↗
PubMed2000

Definition of distinct compartments in polarized Madin-Darby canine kidney (MDCK) cells for membrane-volume sorting, polarized sorting and apical recycling.

Previous studies of fibroblasts have demonstrated that recycling of endocytic receptors occurs through a default mechanism of membrane-volume sorting. Epithelial cells require an additional level of polar membrane sorting, but there are conflicting models of polar sorting, some suggesting that it occurs in early endosomes, others suggesting it occurs in a specialized apical recycling endosome (ARE). The relationship between endocytic sorting to the lysosomal, recycling and transcytotic pathways in polarized cells was addressed by characterizing the endocytic itineraries of LDL, transferrin (Tf) and IgA, respectively, in polarized Madin-Darby canine kidney (MDCK) cells. Quantitative analyses of 3-dimensional images of living and fixed polarized cells demonstrate that endocytic sorting occurs sequentially. Initially internalized into lateral sorting endosomes, Tf and IgA are jointly sorted from LDL into apical and medical recycling endosomes, in a manner consistent with default sorting of membrane from volume. While Tf is recycled to the basolateral membrane from recycling endosomes, IgA is sorted to the ARE prior to apical delivery. Quantifications of the efficiency of sorting of IgA from Tf between the recycling endosomes and the ARE match biochemical measurements of transepithelial protein transport, indicating that all polar sorting occurs in this step. Unlike fibroblasts, rab11 is not associated with Tf recycling compartments in either polarized or glass-grown MDCK cells, rather it is associated with the compartments to which IgA is directed after sorting from Tf. These results complicate a suggested homology between the ARE and the fibroblast perinuclear recycling compartment and provide a framework that justifies previous conflicting models of polarized sorting.

Animals↗
PubMed2000

Apical and basolateral endocytic pathways of MDCK cells meet in acidic common endosomes distinct from a nearly-neutral apical recycling endosome.

Quantitative confocal microscopic analyses of living, polarized MDCK cells demonstrate different pH profiles for apical and basolateral endocytic pathways, despite a rapid and extensive intersection between the two. Three-dimensional characterizations of ligand trafficking demonstrate that the apical and basolateral endocytic pathways share early, acidic compartments distributed throughout the medial regions of the cell. Polar sorting for both pathways occurs in these common endosomes as IgA is sorted from transferrin to alkaline transcytotic vesicles. While transferrin is directly recycled from the common endosomes, IgA is transported to a downstream apical compartment that is nearly neutral in pH. By several criteria this compartment appears to be equivalent to the previously described apical recycling endosome. The functional significance of the abrupt increase in lumenal pH that accompanies IgA sorting is not clear, as disrupting endosome acidification has no effect on polar sorting. These studies provide the first detailed characterizations of endosome acidification in intact polarized cells and clarify the relationship between the apical and basolateral endocytic itineraries of polarized MDCK cells. The extensive mixing of apical and basolateral pathways underscores the importance of endocytic sorting in maintaining the polarity of the plasma membrane of MDCK cells.

Animals↗
PubMed2000

Gentamicin traffics rapidly and directly to the Golgi complex in LLC-PK(1) cells.

To study the intracellular mechanisms of aminoglycoside toxicity, we used a 1:1 fluorescent conjugate of Texas Red and gentamicin (TRG) to quantify early uptake dynamics in renal epithelial (LLC-PK(1)) cells. Utilizing a protocol that quenches TRG fluorescence from lysosomes, the bulk of intracellular accumulation, we determined a portion rapidly trafficked directly to the Golgi complex when identified by a FITC-conjugated lectin from Lens culinaris agglutinin (LCA). A kinetic study over 120 min on cells showing total and quenched TRG fluorescence was then carried out, and the fluorescence intensity from the images was quantified. Trafficking of TRG to the Golgi complex occurred within 15 min and accounted for approximately 20% of total cellular accumulation in the kinetic study. Colocalization studies using compartment-specific markers, 6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]hexanoyl sphingosine (C6-NBD ceramide) and LCA, for the TGN trans-Golgi network, and the cis/medial-Golgi compartments, respectively, determined colocalization occurred with both Golgi compartments. These data support the existence of a pathway that directly and rapidly shuttles a portion of internalized gentamicin to the Golgi complex. We believe this pathway may be responsible for the early negative effects seen on protein synthesis in renal proximal epithelia after aminoglycoside administration.

Animals↗
PubMed2000

Optical aberrations and objective choice in multicolor confocal microscopy.

Refinements in design have simplified confocal microscopy to the extent that it has become a standard research tool in cell biology. However, as confocal microscopes have become more powerful, they have also become more demanding of their optical components. In fact, optical aberrations that cause subtle defects in image quality in wide-field microscopy can have devastating effects in confocal microscopy. Unfortunately, the exacting optical requirements of confocal microscopy are often hidden by the optical system that guarantees a sharp image, even when the microscope is performing poorly. Optics manufacturers provide a wide range of microscope objectives, each designed for specific applications. This report demonstrates how the trade-offs involved in objective design can affect confocal microscopy.

Animals↗
PubMed1999

Subcutaneous adrenaline infiltration in paediatric burn surgery.

Paediatric burn surgery may be associated with significant blood loss and postoperative pain. To investigate methods of reducing these symptoms, we studied a prospective series of 29 children with small to medium sized burns. Presurgically both the burn wound and split skin graft donor sites were injected with a 1:500,000 adrenaline solution, to which bupivicaine had been added. No patient required blood transfusion and no patient developed systemic side effects from the injected solution. Four patients required parenteral analgesia, two in the immediate postoperative period and two at first dressing change. In all other patients pain was controlled with oral analgesia alone. Mean graft take in our series was 95%, indicating that this technique does not compromise burn depth assessment, nor impair graft survival.

Anesthetics, Local↗