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Biomedical subjects

A Brooks

Publications and source records attributed to A Brooks.

At least 19 recordsLinked to original sources
PubMed2006

Distinct mechanisms of form-from-motion perception in human extrastriate cortex.

The exquisite sensitivity of the human visual system to form-from-motion (FfM) cues is well documented. However, identifying the neural correlates of this sensitivity has proven difficult, particularly determining the respective contributions of different motion areas in extrastriate visual cortex. Here we measured visual FfM perception and more elementary visual motion (VM) perception in a group of 32 patients suffering from acute posterior brain damage, and performed MRI-based lesion analysis. Our results suggest that severe FfM perception deficits without an associated deficit of VM perception are due to damage to ventral occipito-temporal cortex (VOT), whereas associated deficits of FfM and VM perception are due to damage either in proximity to area MT+/V5 or an area including lateral occipital complex (LOC) and VOT. These data suggest the existence of at least three functionally and anatomically distinct regions in human visual cortex that process FfM signals.

Adult↗
PubMed2006

Compensation of strong thermal lensing in high-optical-power cavities.

In an experiment to simulate the conditions in high optical power advanced gravitational wave detectors, we show for the first time that the time evolution of strong thermal lenses follows the predicted infinite sum of exponentials (approximated by a double exponential), and that such lenses can be compensated using an intracavity compensation plate heated on its cylindrical surface. We show that high finesse approximately 1400 can be achieved in cavities with internal compensation plates, and that mode matching can be maintained. The experiment achieves a wave front distortion similar to that expected for the input test mass substrate in the Advanced Laser Interferometer Gravitational Wave Observatory, and shows that thermal compensation schemes are viable. It is also shown that the measurements allow a direct measurement of substrate optical absorption in the test mass and the compensation plate.

Journal Article↗
PubMed2006

Auditory motion affects visual biological motion processing.

The processing of biological motion is a critical, everyday task performed with remarkable efficiency by human sensory systems. Interest in this ability has focused to a large extent on biological motion processing in the visual modality (see, for example, Cutting, J. E., Moore, C., & Morrison, R. (1988). Masking the motions of human gait. Perception and Psychophysics, 44(4), 339-347). In naturalistic settings, however, it is often the case that biological motion is defined by input to more than one sensory modality. For this reason, here in a series of experiments we investigate behavioural correlates of multisensory, in particular audiovisual, integration in the processing of biological motion cues. More specifically, using a new psychophysical paradigm we investigate the effect of suprathreshold auditory motion on perceptions of visually defined biological motion. Unlike data from previous studies investigating audiovisual integration in linear motion processing [Meyer, G. F. & Wuerger, S. M. (2001). Cross-modal integration of auditory and visual motion signals. Neuroreport, 12(11), 2557-2560; Wuerger, S. M., Hofbauer, M., & Meyer, G. F. (2003). The integration of auditory and motion signals at threshold. Perception and Psychophysics, 65(8), 1188-1196; Alais, D. & Burr, D. (2004). No direction-specific bimodal facilitation for audiovisual motion detection. Cognitive Brain Research, 19, 185-194], we report the existence of direction-selective effects: relative to control (stationary) auditory conditions, auditory motion in the same direction as the visually defined biological motion target increased its detectability, whereas auditory motion in the opposite direction had the inverse effect. Our data suggest these effects do not arise through general shifts in visuo-spatial attention, but instead are a consequence of motion-sensitive, direction-tuned integration mechanisms that are, if not unique to biological visual motion, at least not common to all types of visual motion. Based on these data and evidence from neurophysiological and neuroimaging studies we discuss the neural mechanisms likely to underlie this effect.

Acoustic Stimulation↗
PubMed2006

CMV-specific CD8 T-cell dynamics in the blood and the lung allograft reflect viral reactivation following lung transplantation.

Despite the potentially high burden of cytomegalovirus (CMV)-related disease following lung transplantation, the role of the cytotoxic T-lymphocyte (CTL) response to CMV in this patient group is ill-defined. We assessed the CMV-specific T-cell response in the blood and lung allograft of immunosuppressed lung transplant recipients receiving antiviral prophylaxis and following their withdrawal. While the proportion of CMV-specific CTL varied between patients, in the absence of CMV reactivation the level of CMV-specific CD8+ T cells in the blood remained stable over time. In the majority of patients CMV-specific cells could be detected in the lung allograft, often in the absence of viral DNA. Additionally, following primary CMV lung infection, CMV-specific CD8+ T cells were detected no earlier than 100 days post-transplantation but still prior to the detection of viral DNA in the lung allograft. Together these findings suggest that very low levels of CMV replication are sufficient to both prime and recruit CMV-specific CD8+ T cells to the MHC-mismatched lung allograft. The direct detection of CMV-specific T cells with an effector phenotype in the lung allograft suggests a protective antiviral function. This study provides a framework upon which the association between CMV and chronic allograft rejection can be further studied.

Adult↗
PubMed2006

Improving immunization coverage through budgeted microplans and sub-national performance agreements: early experience from Cambodia.

In recent years, Cambodia has demonstrated significant success in specific aspects of immunization with gains through campaign efforts in measles control and polio eradication. In contrast, routine immunization rates have failed to improve over the last five years. In response, the National Immunization Program of the Ministry of Health developed a coverage improvement planning (CIP) process. This paper describes the CIP process in Cambodia, including identified barriers to and strategies for improving coverage. Immunization coverage rose in 8 of 10 pilot districts in the year following the introduction of CIP in 2003. The mean increase in DPT3 coverage across pilot districts on an annual basis was 16%, which provides encouraging early evidence for the effectiveness of the intervention. Factors associated with success in coverage improvement included: (1) development of a needs-based micro-plan, (2) application of performance-based contracting between levels of management, (3) investment in social mobilization, (4) securing finance for health outreach programs and (5) strengthened monitoring systems. Lessons learned will guide program expansion to improve immunization coverage nationally.

Cambodia↗
PubMed2005

The relationship between impaired decision-making, sensation seeking and readiness to change in cigarette smokers.

OBJECTIVE: The study investigated whether impaired decision-making as measured by the Gambling Task and Sensation Seeking, on one hand, and nicotine-dependence and readiness to change, on the other hand, show mutual influences in cigarette smokers. METHODS: Cigarette smokers were classified as dependent or non-dependent smokers. Assessment included stages of change (RCQ), decisional balance (DBS), Sensation Seeking Scale Form-V (SSS-V), and performance on the Gambling Task (GT). RESULTS: With the exception of a significant higher score in the SSS-V subscale Experience Seeking in dependent smokers, correlations between nicotine-dependence and cognitive features were not significant. The directions of the non-significant differences were not consistent. No significant relationship was found between the SSS-V and the GT, on one hand, and the readiness to change smoking behaviour, on the other hand. CONCLUSIONS: The results of the present study suggest that impaired performance on the GT and high scores in Sensation Seeking do not play an important role in nicotine-dependence and readiness to change smoking behaviour or vice versa.

Adaptation, Psychological↗
PubMed2004

Factors affecting outcome in penetrating oesophageal trauma.

BACKGROUND: Penetrating oesophageal trauma is rare and the risk factors affecting outcome have not been clearly identified. Delayed management has been cited as a factor contributing to the high rates of morbidity and mortality, but evidence for this is lacking. METHODS: A retrospective study was undertaken of patients with penetrating oesophageal trauma presenting to a level I trauma centre over 8 years. Outcome was assessed in terms of mortality, morbidity (oesophageal and non-oesophageal), and length of hospital and intensive care unit (ICU) stays. RESULTS: Fifty-two patients with oesophageal injury who reached the operating theatre were included. The overall mortality rate was 6 per cent. Fifteen patients (29 per cent) developed oesophageal injury-related complications. Time from injury to management was the only important risk factor for the development of oesophageal complications (P = 0.001), but did not affect the length of ICU (P = 0.560) or hospital (P = 0.329) stay, incidence of non-oesophageal injury-related complications (P = 0.963) or death (P = 0.937). Patients with gunshot injuries spent longer in the ICU (P = 0.007) and the duration of hospital stay was longer for those with higher-grade oesophageal injuries (P = 0.025). CONCLUSION: The risk of oesophageal injury-related complications was directly related to the interval between the trauma and definitive management of the oesophageal injury.

Adolescent↗
PubMed2004

Toxicity of the entomopathogenic fungus, Metarhizium anisopliae (Deuteromycotina: Hyphomycetes) to adult females of the blowfly Lucilia sericata (Diptera: Calliphoridae).

The fungus Metarhizium anisopliae (Metchnikoff) (Deuteromycotina: Hyphomycetes) is a natural component of soil flora world-wide and is a causal agent of the green muscardine diseases of insects. The use of this pathogen as a potential biocontrol agent against adult females of the blowfly, Lucilia sericata (Meigen) (Diptera: Calliphoridae) was considered. The blowfly L sericata is an economically important agent of cutaneous myiasis of sheep, particularly in northern Europe. Exposure of flies to suspensions of fungal spores by immersion, topical application or tarsal contact with treated surfaces all resulted in high levels of fatal infection. Spores suspended in silicone oil resulted in higher levels of infection (50-70%) than those formulated in a 0.3 glitre(-1) solution of the detergent Tween 80 (10-20%). Spore concentration had a significant effect on levels of infection of flies, with the highest levels of mortality (64%) resulting from a suspension of 1 x 10(7) conidia ml(-1). The duration of tarsal contact had a significant effect on levels of infection. Mean infection levels of 30% were observed following exposure of free-flying adults to a single spore-treated, 5 x 15 cm2 cloth surface suspended from the roof of a cage (30 cm cube). The implications of the results for the potential use of M anisopliae in the biocontrol of blowflies are discussed.

Animals↗
PubMed2004

Emergency ultrasound in the acute assessment of haemothorax.

AIMS: To evaluate thoracic ultrasound for the detection of haemothorax in patients with thoracic trauma against established investigations. METHODS: Thoracic ultrasound was performed as an extension of the standard focused assessment with sonography for trauma (FAST) protocol used at the Queen's Medical Centre for the assessment of adult patients with torso trauma. Fluid was sought in both pleural cavities using a hand portable ultrasound system by one of two non-radiologists trained in FAST. Findings were compared against subsequent investigations/procedures performed at the discretion of the attending emergency physician-supine chest radiography, intercostal drain, computed tomography, or thoracotomy. The sensitivity of the technique and the time taken to diagnosis for each investigation were recorded. RESULTS: Sixty one patients, 54 (89%) after blunt trauma, underwent thoracic ultrasound evaluation during the study. Twelve patients had a haemothorax detected by ultrasound and confirmed by computed tomography or by tube thoracostomy. Four haemothoraces detected on ultrasound were not apparent on trauma chest radiography. There were 12 true positives, 48 true negatives, no false positives, and one false negative scan. The sensitivity of ultrasound was 92% and specificity 100% with a positive predictive value of 100% and negative predictive value 98% for the detection of haemothorax after trauma. CONCLUSIONS: Emergency ultrasound of the chest performed as part of the primary survey of the traumatised patient can rapidly and accurately diagnose haemothorax and is a valuable tool to augment the immediate clinical assessment of these patients.

Acute Disease↗
PubMed2004

Prospective evaluation of non-radiologist performed emergency abdominal ultrasound for haemoperitoneum.

OBJECTIVES: To evaluate non-radiologist performed emergency ultrasound for the detection of haemoperitoneum after abdominal trauma in a British accident and emergency department. METHODS: Focused assessment with sonography for trauma (FAST) was performed during the primary survey on adult patients triaged to the resuscitation room with suspected abdominal injury over a 12 month period. All investigations were performed by one of three non-radiologists trained in FAST. The ultrasound findings were compared against the investigation of choice of the attending surgeon/accident and emergency physician. The patients were followed up for clinically significant events until hospital discharge or death. RESULTS: One hundred patients who had sustained blunt abdominal trauma, were evaluated by FAST. Nine true positive scans were detected and confirmed by computed tomography, diagnostic peritoneal lavage, or laparotomy. There was one false positive in this group, giving a sensitivity of 100%, specificity 99%, and positive predictive value of 90%. Ten patients with penetrating injuries were evaluated with a sensitivity and specificity for FAST of 33% and 86% respectively. CONCLUSIONS: Emergency torso ultrasound for the detection of haemoperitoneum can be successfully performed by trained non-radiologists within a British accident and emergency system. It is an accurate and rapid investigation for blunt trauma, but the results should be interpreted with caution in penetrating injury.

Abdominal Injuries↗
PubMed2004

Emergency surgery in patients in extremis from blunt torso injury: heroic surgery or futile care?

BACKGROUND: Trauma strikes unexpectedly, frequently in the young and fit. When trauma victims arrive in the emergency room all possible steps, including surgery, are often undertaken in an attempt to achieve a successful outcome. However, for patients presenting in extremis, with cardiac arrest or exsanguinating blunt chest injury, the results of resuscitation and emergency surgery are extremely poor. PATIENTS AND SETTING: Eight patients in extremis with a mean injury severity score of 36, presented to the resuscitation room of Queens Medical Centre during 2001. On arrival all were in extremis or cardiac arrest after significant blunt injury to the torso, and during resuscitation had a brief loss of cardiac output. They underwent emergency surgery to control haemorrhage and correct injuries in an attempt to preserve life. Seven patients died within hours of their initial presentation either in theatre or the intensive care unit and one patient survived. CONCLUSIONS: Futile care in the management of severely injured patients is a controversial concept although the literature defines four concepts of futility within surgery. At present, while there remains even the remotest possibility of survival, there remains a strong incentive to act and reports of isolated survivors from studies of trauma patients in extremis or cardiac arrest continue to emerge. This may be seen as justification for either an aggressive surgical approach or an indication that surgery is futile. In an emerging culture of guidelines regarding effectiveness of treatment, is this an area in which such guidelines can or should be applied?

Accidents, Traffic↗
PubMed2002

Diagnostic peritoneal lavage analysis: should trauma guidelines be revised?

OBJECTIVES: Diagnostic peritoneal lavage (DPL) is used to detect intraperitoneal bleeding in patients sustaining blunt and penetrating abdominal trauma. The procedure should be performed by an experienced general surgeon, and the fluid obtained analysed by haematology technicians. Current Advanced Trauma Life Support guidelines are very clear on what constitutes a positive result, mandating laparotomy. The aim of this work was to assess whether DPL could actually be performed in practice. METHODS: A telephone survey was performed of a random selection of haematology technicians in 40 major trauma units in the UK, to assess whether they could actually analyse a DPL sample if it were sent to them. This was performed both during the day, and "out of hours". Secondly the experience of performing DPL was determined among 1797 general surgical trainees and consultants, by means of a questionnaire. RESULTS: Between 9 am and 5 pm 29 of 40 haematology technicians questioned were able to analyse a sample of DPL fluid. This compared with a figure of 9 of 40 when the questionnaire was administered "out of hours". A total of 854 (48%) questionnaires were received from surgical trainees and consultants. Approximately 60% of those questioned had performed less than 10 DPLs throughout the whole of their careers. DISCUSSION: These results suggest that UK surgeons have little experience in performing DPL, and even if they do it is unlikely that any haematology departments will be able to analyse the sample, especially if performed after 5 pm. ATLS guidelines should be changed, and this investigation abandoned in favour of abdominal ultrasound.

Abdominal Injuries↗
PubMed2002

Prospective evaluation of handheld ultrasound in the diagnosis of blunt abdominal trauma.

OBJECTIVES: To evaluate the Sonosite 180 handheld ultrasound in the diagnosis of haemoperitoneum in blunt abdominal trauma. METHODS: Trauma ultrasound using the Focused Assessment with Sonar for Trauma (FAST) technique was performed using the Sonosite 180 handheld ultrasound during the primary survey of adult patients triaged to the resuscitation room with multiple trauma or suspected abdominal injury. The ultrasound findings were compared against the investigation of choice of the attending surgeon/accident & emergency physician--CT, DPL, laparotomy or clinical observation. RESULTS: 50 patients who had sustained blunt abdominal trauma were evaluated using FAST. Satisfactory images were obtained in 96%. There were 5 true positive scans confirmed by CT, DPL or laparotomy. There were no false negative or false investigations. The sensitivity and specificity of handheld FAST was 100%. CONCLUSIONS: Handheld ultrasound using the Sonosite 180 system can be successfully used by appropriately trained doctors as the primary investigation in the acute evaluation of blunt abdominal trauma.

Abdominal Injuries↗
PubMed2002

The experience and training of British general surgeons in trauma surgery for the abdomen, thorax and major vessels.

BACKGROUND: The report Better Carefor the Severely Injured [London: The Royal College of Surgeons of England and the British Orthopaedic Association; 2000] states that an experienced general surgeon trained in the techniques required to perform life-saving emergency surgery is vital in the management of major trauma. The experience and training of general surgeons in the UK in the management of trauma to the abdomen, thorax and major vessels has never been assessed. METHOD: Postal questionnaire sent to UK general surgical consultants and Higher Surgical Trainees (HSTs). RESULTS: A total of 854 (48%) questionnaires were completed. Of respondents, 85% believe that major trauma should be directed to hospitals that provide a dedicated trauma service. Of non-vascular specialists, 43% felt their training was adequate to manage vascular trauma and only one-third of general surgical consultants felt adequately prepared to manage acute cardiothoracic injuries. The median number of trauma laparotomies undertaken annually was 2 for blunt injury and 1 for penetrating injury. Of HSTs, 21% had not performed a splenectomy for trauma and 44% had no experience of packing for liver injuries. CONCLUSIONS: There is limited experience and training in the surgical management of torso trauma in the UK. Implementation of the recommendations from Better Care for the Severely Injured will be hampered unless steps are taken to maximise experience and improve training.

Abdominal Injuries↗