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Biomedical subjects

B Webb

Publications and source records attributed to B Webb.

At least 19 recordsLinked to original sources
PubMed2006

A model of antennal wall-following and escape in the cockroach.

Cockroaches exploit tactile cues from their antennae to avoid predators. During escape running the same sensors are used to follow walls. We hypothesise that selection of these mutually exclusive behaviours can be explained without representation of the stimulus or an explicit switching mechanism. A neural model is presented that embodies this hypothesis. The model incorporates behavioural and neurophysiological data and is embedded in a mobile robot in order to test the response to stimuli in the real world. The system is shown to account for data on escape direction and high-speed wall-following in the cockroach, including the counter-intuitive observation that faster running cockroaches maintain a closer distance to the wall. The wall-following behaviour is extended to include discrimination of tactile escape cues according to behavioural context. We conclude by highlighting questions arising from the robot experiments that suggest interesting hypotheses to test in the cockroach.

Animals↗
PubMed2005

Detection of HCV and HIV-1 antibody negative infections in Scottish and Northern Ireland blood donations by nucleic acid amplification testing.

BACKGROUND AND OBJECTIVES: To reduce the risk of transfusion-transmissible viruses entering the blood supply, the nucleic acid amplification testing (NAT) was implemented to screen Scottish and Northern Irish blood donations in minipools. After 5 years of NAT for hepatitis C virus (HCV) and 2 years for human immunodeficiency virus-1 (HIV-1), the yield of serologically negative, nucleic acid positive 'window donations' and cost-benefit of NAT is under review. MATERIALS AND METHODS: When the Scottish National Blood Transfusion Service (SNBTS) implemented NAT in 1999, a fully automated 'black box' system was not available. Therefore, an 'in-house' assimilated NAT assay was developed, validated and implemented. The system is flexible and allows testing for additional viral markers to be introduced with relative ease. RESULTS: The HCV and HIV NAT assays have 95% detection levels of 7.25 IU/ml and 39.8 IU/ml, respectively, as determined by probit analysis. One HCV (1 in 1.9 million) and one HIV (1 in 0.77 million) window donation have been detected in 5 and 2 years, respectively, of NAT. CONCLUSION: The SNBTS NAT assays are robust and have performed consistently over the last 5 years. The design of the in-house system allowed HIV NAT to be added in 2003 at a relatively small additional cost per sample, although for both assays, the royalty fee far exceeds the cost of the test itself. Clearly NAT has a benefit in improving the safety of the blood supply although the risks of transfusion-transmitted viral infections, as reported in the Serious Hazards of Transfusion (SHOT) report, are extremely low. Also, in UK the yield of HCV antibody negative, NAT positive donations is far lower than predicted although the early detection of an HIV window period donation and the increase of HIV in the blood donor and general populations may provide a stronger case for HIV NAT. SUMMARY SENTENCE: The yield of HCV and HIV NAT in UK is significantly less than that anticipated from statistical models.

Adult↗
PubMed2001

Solution structure of the carboxyl-terminal cysteine-rich domain of the VHv1.1 polydnaviral gene product: comparison with other cystine knot structural folds.

Polydnaviruses are an unusual group of insect viruses that have an obligate symbiotic association with certain parasitic wasps. These viruses are transmitted with the wasp egg during oviposition into lepidopteran insects, enabling the survival and development of the egg inside the host larvae. We report the three-dimensional structure of a novel polydnaviral cysteine-rich motif (cys-motif), identified as the carboxyl-terminal domain of a two cys-motif containing polydnaviral VHv1.1 gene product, abbreviated "C-term VHv1.1". This 65-residue domain was identified experimentally by limited proteolysis of the full-length protein and was subsequently cloned in a bacterial expression system for NMR studies. The C-term VHv1.1 3D structure was determined in solution by two-dimensional (1)H NMR spectroscopy. Calculation of the structure was based on a total of 300 upper distance restraints and 20 dihedral angle constraints, and resulted in an ensemble of 25 representative conformers with an average rmsd of 0.47 A from the mean structure for core backbone atoms. The protein core is made of a four beta-strand scaffold held together in a compact structure by three disulfide bonds, which form a cystine knot. The four beta-strands are arranged in an unusual configuration to form a triple-stranded beta-sheet and double-stranded beta-sheet. Comparison with other classes of cystine knots provides indication that C-term VHv1.1 represents a new and distinct cystine knot motif. This analysis provides a structural basis for interpretation of the genetic and amino acid sequence data classifying polydnavirus gene products as members of cysteine-rich protein families.

Amino Acid Sequence↗
PubMed2001

Can robots make good models of biological behaviour?

UNLABELLED: How should biological behaviour be modelled? A relatively new approach is to investigate problems in neuroethology by building physical robot models of biological sensorimotor systems. The explication and justification of this approach are here placed within a framework for describing and comparing models in the behavioural and biological sciences. First, simulation models--the representation of a hypothesis about a target system--are distinguished from several other relationships also termed "modelling" in discussions of scientific explanation. Seven dimensions on which simulation models can differ are defined and distinctions between them discussed: 1. RELEVANCE: whether the model tests and generates hypotheses applicable to biology. 2. Level: the elemental units of the model in the hierarchy from atoms to societies. 3. Generality: the range of biological systems the model can represent. 4. Abstraction: the complexity, relative to the target, or amount of detail included in the model. 5. Structural accuracy: how well the model represents the actual mechanisms underlying the behaviour. 6. Performance match: to what extent the model behaviour matches the target behaviour. 7. Medium: the physical basis by which the model is implemented. No specific position in the space of models thus defined is the only correct one, but a good modelling methodology should be explicit about its position and the justification for that position. It is argued that in building robot models biological relevance is more effective than loose biological inspiration; multiple levels can be integrated; that generality cannot be assumed but might emerge from studying specific instances; abstraction is better done by simplification than idealisation; accuracy can be approached through iterations of complete systems; that the model should be able to match and predict target behaviour; and that a physical medium can have significant advantages. These arguments reflect the view that biological behaviour needs to be studied and modelled in context, that is, in terms of the real problems faced by real animals in real environments.

Behavior↗
PubMed2001

An exploratory study in a community National Health Service Trust to understand why enrolled nurses choose not to convert to first-level registration.

AIM: The aim of this research study was to more fully understand at local level what it was that prevented enrolled nurses (ENs) coming forward for conversion to the first level of the United Kingdom Central Council for Nursing, Midwifery and Health Visiting (UKCC) nursing register. BACKGROUND: An NHS Trust had first-level nursing shortages and looked to the 69 ENs nurses -- 12% of the nursing workforce -- to meet that shortfall via conversion to first-level UKCC nurse registration. Based on local surveys, their intention to convert was the same as national findings, in that high numbers said they wanted to convert. In addition, this NHS Trust provided support and fully funded conversion courses, yet they did not come forward. METHODS: A qualitative approach based on focus groups with ENs was adopted to research this 'problem' within the local organizational context. FINDINGS: ENs were unaware that fully funded course places were available, extremely fearful of the academic expectations of the conversion course and highly committed to family needs. Conclusions Nationally, policymakers advocated the retention of and/or the conversion of ENs, on the grounds that research participants did not perceive or believe that managers were supportive of this proposal. KEY RECOMMENDATIONS: Create managers who looked beyond the immediate 'problem' of nursing shortages and invested in ENs to retain them in the NHS workforce. Establish local policy and an implementation plan to address the needs of ENs in line with clinical governance and the local nurse retention strategy. Empower ENs who would secure solutions to the issues for themselves.

Career Choice↗
PubMed2001

Demonstration of different patterns of musculoskeletal, soft tissue and visceral involvement in melioidosis using 99m Tc stannous colloid white cell scanning.

Melioidosis is an infectious disease that can present with multiple foci of disease involvement. Assessment of disease extent can be difficult, especially in musculoskeletal, visceral and soft tissue infection. This study examined the usefulness of white cell scans in this condition. 99mTc stannous colloid white cell scanning was performed in 21 patients with culture-proven melioidosis. Scan results were compared with clinical assessment and correlated with other forms of imaging. White cell scans demonstrated all but one of the clinically apparent sites of musculoskeletal, visceral and other soft tissue infection. Unsuspected disseminated soft tissue lesions were seen in two patients, including femoral node uptake in both, and these patients subsequently presented with relapsing musculoskeletal disease. Unsuspected musculoskeletal disease was found in one patient. Clinically suspected musculoskeletal disease was accurately excluded by white cell scan in another patient. The results of white cell scanning were also examined in disease of other viscera. Renal and prostatic disease were visualized. Unsuspected parotid involvement was found in two patients. Only one of two spinal lesions was visualized. Pulmonary disease was not necessarily associated with abnormal uptake. White cell scanning is a quick and effective way of assessing the extent of musculoskeletal, visceral and soft tissue disease in melioidosis.

Adult↗
PubMed2001

View from the boundary.

Re-implementing biological mechanisms on robots not only has technological application but can provide a unique perspective on the nature of sensory processing in animals. To make a robot work, we need to understand the function as part of an embodied, behaving system. I argue that this perspective suggests that the terms "representation" and "information processing" can be misleading when we seek to understand how neurobiological mechanisms carry out perceptual processes. This argument is presented here with reference to a robot model of cricket behavior, which has demonstrated competence comparable to that of the insect, but utilizes surprisingly simple central processing. Instead it depends on sensory interfaces that are well matched to the task, and on the link between environment, action, and perception.

Animals↗
PubMed2000

What does robotics offer animal behaviour?

There is a growing body of robot-based research that makes a serious claim to be a new methodology for biology. Robots can be used as models of specific animal systems to test hypotheses regarding the control of behaviour. At levels from learning algorithms to specific dendritic circuits, implementing a proposed controller in a robotic device tests it against real environments in a way that is difficult to simulate. This often provides insight into the true nature of the problem. It also enforces complete specifications and combines bodies of data. Current work can sometimes be criticized for drawing unjustified conclusions given the limited evaluation and inevitable inaccuracies of robot models. Nevertheless, this approach has led to novel hypotheses for animal behaviour and seems likely to provide fruitful results in the future. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

MnSOD expression is increased in metastatic gastric cancer.

BACKGROUND: Manganese superoxide dismutase (MnSOD) catalyzes the scavenging of superoxide radicals in order to protect cells from the damage caused by reactive oxygen species. Previous studies implicate MnSOD in cancer progression, but its role in gastric cancer metastasis is poorly understood. MATERIALS AND METHODS: To determine whether MnSOD expression correlates with gastric cancer metastasis, we compared immunostaining for MnSOD in the primary tumors of gastric cancer patients with (n = 15) and without (n = 9) nodal metastases. These patients were matched for risk factors associated with gastric cancer metastasis, such as tumor site, depth, and grade. MnSOD expression was scored positive (increased) if MnSOD staining of tumor cells was more intense than MnSOD staining in corresponding normal gastric epithelial cells. Statistical analyses were via chi(2) test and Fisher's exact test. RESULTS: MnSOD expression was increased in 14 of the 15 (93%) metastatic tumors, compared to only 4 of the 9 (44%) nonmetastatic tumors (P = 0.015). There was no significant difference in staining when the two groups were compared based on tumor grade (P = 0.70) or depth of tumor cell invasion (T stage) (P = 0.22). CONCLUSIONS: MnSOD expression is upregulated in the primary tumors of gastric cancer patients with lymph node metastases. This finding supports an involvement of MnSOD and possibly the reactive oxygen status of the gastric tumor microenvironment in gastric cancer metastasis.

Adult↗
PubMed2000

A simple latency-dependent spiking-neuron model of cricket phonotaxis.

A simple hypothesis regarding the recognition behaviour of crickets for conspecific songs is implemented in a dynamic simulation of spiking neurons and tested on a robot base. The model draws on data from cricket neurophysiology but requires only four neurons to reproduce a wide range of the observed behaviour. The directional response depends on relative latencies in firing onset, and the 'recognition' emerges from the implicit filtering properties of leaky-integrate-and-fire neurons. Experimental conditions reproduced include tests of syllable rate preference, song from above with sound from one side, and choice between songs. The robot produces behaviour closely comparable to the cricket in all but a 'split-song' condition. A number of properties can be observed in the neural circuit that correspond to cricket neurophysiology including apparent 'recognition neurons'. Limitations of the model, extensions and alternative models are discussed.

Action Potentials↗
PubMed2000

Enrolled nurse conversion: a review of the literature.

AIM: The aim of this literature review was to examine the policies and professional literature from the last 50 years about the introduction, the role and subsequent plight of the enrolled nurse (also known as second level nurses), and the need to convert to the first level of the UKCC nursing register. BACKGROUND: Nurse shortages within the NHS have been cyclical since its inception in 1948. The policy decision to cease the training of enrolled nurses within the frame of modernizing the education and training of the nursing workforce had two distinct implications for enrolled nurses. Firstly, they could choose to stay as enrolled nurses or convert to first level nursing. Nevertheless, enrolled nurses have cited the lack of funded conversion course places, and managerial support for non-conversion. METHODS: A critical review of the national policies and professional literature concerned with the evaluation of enrolled nurses' contribution to the NHS. FINDINGS: It was argued that national policy needs to be supported on the ground, whereby enrolled nurses are proactively supported to come forward for conversion and/or meaningful roles are created and sustained where enrolled nurses continue to make a valuable contribution to the NHS agenda. Finally, the paper challenges all NHS organizations to consider the profile and value of enrolled nurses and become proactive in their recruitment and retention of this nursing group.

Education, Nursing, Baccalaureate↗
PubMed1999

The development and pharmacological characterization of calcium channel currents in cultured embryonic rat septal cells.

We characterized the development and pharmacology of Ca(2+) channel currents in NGF-treated embryonic day 21 cultured rat septal cells. Using standard whole-cell voltage clamp techniques, cells were held at -80 mV and depolarized to construct current-voltage relations in conditions that eliminated Na(+) or K(+) currents. Barium (10 mM) was used as the charge carrier. Maximum current was produced when cells were depolarized to 0 or +10 mV. Recordings from 77 cells revealed that Ca(2+) channel current density increases over time in culture from nearly 0 pA/pF on day 2 in vitro (0.65+/-0.65 pA/pF) to (6.95+/-1.59 pA/pF) on days 6-8. This was followed by a period where currents became nearly 3 times more dense (21.05+/-7.16 pA/pF) at days 9-17. There was little or no evidence for low voltage activated currents. Bath application of 50-100 microM CdCl(2) abolished approximately 95% of the current. Application of 10 microM nimodipine produced a 50.5+/-3.22% reduction in current, 2 microM omega-CTx-GVIA produced a 32.4+/-7.3% reduction, and application of 4 microM omega-Aga-IVA produced a 29.5+/-5.73% reduction in current. When all three inhibitors (10 microM nimodipine, 2 microM omega-CTx-GVIA, and 4 microM omega-Aga-IVA) were applied simultaneously, a residual current remained that was 18.0+/-4.9% of the total current and was completely abolished by application of CdCl(2). This is the first report to characterize Ca(2+) channel currents in cultured embryonic septal cells. These data indicate that there is a steady increase in Ca(2+) channel expression over time in vitro, and show that like other cultured neuronal cells, septal cells express multiple Ca(2+) channel types including L, N, P/Q and R-type channels.

Animals↗
PubMed1999

Squamous cell papillomatosis of esophagus following placement of a self-expanding metal stent.

The esophageal self-expanding metal stent has gained widespread acceptance for the management of tracheoesophageal fistulas and the palliative management of malignant esophageal strictures. The complications associated with its use can be classified as either immediate or delayed. The most frequent delayed complications include tumor ingrowth, stent migration, reflux of gastric contents, bleeding, and perforation. This case report illustrates an otherwise unrecognized delayed complication of a self-expanding metal stent. Near complete ingrowth of the stent by squamous mucosal hyperplasia occurred within six weeks of the metal stent's placement. This finding supports the hypothesis that mucosal injury and regeneration underlies the etiology of esophageal squamous cell papilloma formation.

Adenocarcinoma↗
PubMed1999

A framework for models of biological behaviour.

Modelling is most clearly understood as a adjunct in the process of deriving predictions from hypotheses. By representing a hypothesised mechanism in a model we hope by manipulating the model to understand the hypotheses' consequences. Eight dimensions on which models of biological behaviour can vary are described: the degree of realism with which they apply to biology; the level of biology they represent; the generality or range of systems the model is supposed to cover; the abstraction or amount of biological detail represented; the accuracy of representation of the mechanisms; the medium in which the model is built; the match of the model behaviour to biological behaviour; and the utility of the model in providing biological understanding and/or technical insight. It is hoped this framework will help to clarify debates over different approaches to modelling, particularly by pointing out how the above dimensions are relatively independent and should not be conflated.

Animals↗
PubMed1999

A neuromorphic hair sensor model of wind-mediated escape in the cricket.

Crickets are able to extract directional information about a wind stimulus through the filiform hairs located on their cerci. This paper describes the design and testing of a neuromorphic sensor that aims to achieve a close correlation with both the physical and functional properties of these hairs. An integrate and fire neural network is used to process the sensory information in real time. The resulting system is shown to be capable of extracting directional information from a wind stimulus and producing an appropriate motor control pattern.

Action Potentials↗
PubMed1999

Experience in treating recalcitrant scalp psoriasis with automated shampooing and debridement.

We report the cumulative clinical experience and financial implications of treating severe scalp psoriasis in an outpatient phototherapy center by means of an automated scalp debridement unit. Benefits of this approach included increased patient and staff satisfaction, enhanced response of recalcitrant scalp psoriasis, and detection of scalp dermatoses mimicking psoriasis.

Adolescent↗