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Biomedical subjects

N Evans

Publications and source records attributed to N Evans.

At least 19 recordsLinked to original sources
PubMed2006

Degradation of tetraphenylphosphonium bromide at high pH and its effect on radionuclide solubility.

Recently, tetraphenylphosphonium bromide (TPPB) has been used to remove technetium from some radioactive waste streams. However, before TPPB could be approved for use it was necessary to show that TPPB and its degradation products would not have a significant detrimental effect on post-closure performance of a radioactive waste repository. TPPB is known to be stable at neutral pH, however, under alkaline conditions it degrades by an alkaline hydrolysis mechanism to triphenylphosphonium oxide (TPPO). Degradation can also occur by radiolysis to produce triphenylphosphine (TPP). The kinetics of the alkaline hydrolysis degradation of TPPB is described and the solubility of europium, iodine, nickel, technetium(VII) and uranium(VI) in aqueous solutions of TPPB and its degradation products is reported. These results were used to support the use of TPPB in removing technetium from some waste streams.

Hydrolysis↗
PubMed2006

Prenatal predictors of mortality in very preterm infants cared for in the Australian and New Zealand Neonatal Network.

AIM: To identify antenatal and perinatal risk factors for in-hospital mortality of babies born within the Australian and New Zealand Neonatal Network (ANZNN). METHODS: Data were collected prospectively as part of the ongoing audit of high-risk infants (birth weight <1500 g or gestation <32 weeks) admitted to all level III neonatal units in Australia and New Zealand. Antenatal and intrapartum factors to 1 min of age were examined in 11 498 infants with gestational age >24 weeks. Risk and protective factors for mortality were derived from logistic regression models fitted to 1998-9 data and validated on 2000-1 data. RESULTS: For the whole cohort of infants born between 1998 and 2001, prematurity was the dominant risk factor, infants born at 25 weeks having 32 times greater odds of death than infants born at 31 weeks. Low birth weight for gestational age also had a dose-response effect: the more growth restricted the infant the greater the risk of mortality; infants below the 3rd centile had eight times greater odds of death than those between the 25th and 75th centiles. Male sex was also a significant risk factor (odds ratio (OR) 1.55, 95% confidence interval (CI) 1.31 to 1.82). Maternal hypertension in pregnancy was protective (OR 0.46, 95% CI 0.36 to 0.50). The predictive model for mortality had an area under the receiver operating characteristic curve of 0.82. CONCLUSIONS: Risk of mortality can be predicted with good accuracy with factors up to the 1 min Apgar score. By using gestation rather than birth weight as the main indicator of maturity, these data confirm that weight for gestational age is an independent risk factor for mortality.

Australasia↗
PubMed2006

Dermal nickel exposure associated with coin handling and in various occupational settings: assessment using a newly developed finger immersion method.

BACKGROUND: The role of nickel in causing hand dermatitis in some occupations has been difficult to assess due to problems with reliable measurement of the exposure to nickel in the workplace and lack of a definitive threshold for nickel allergic contact dermatitis. It is not uncommon to find nickel allergy on patch testing but it is difficult to determine whether this is of relevance to occupational nickel exposure or simply a reflection of past exposure to nickel-plated jewellery or other nonoccupational nickel exposure. OBJECTIVES: To devise a simple and reproducible method to quantify the amount of nickel on the skin and to apply the technique to measure dermal nickel exposure in various occupational settings. METHODS: A rapid and simple sampling procedure was developed for determination of nickel on the skin of workers potentially exposed to nickel by exposing individuals to nickel-releasing coins and measuring exposure by immersing the exposed thumbs and index fingers directly into graduated sample tubes containing ultrapure water and aqueous nickel extracts. The solutions were analysed by inductively coupled plasma-optical emission spectrometry after stabilization with nitric acid. The method shows advantages over alternatives such as wipe testing and tape stripping in terms of extraction efficiency, speed and ease of operation in the field. A pilot survey of dermal nickel exposure for workers in several occupational settings was conducted. RESULTS: The study suggested that a 'normal' level of nickel on the skin is <10 ng cm(-2). Coin handling induced an appreciable increase in the amount of nickel on the skin within 2 min. Experiments indicated a linear relationship between coin handling (exposure time) and measured dermal nickel levels following standardized coin handling. A pilot survey, conducted among cashiers, shop assistants, bar staff, hairdressers and workers in the nickel industry revealed dermal nickel concentrations ranging from <0.9 to 7160 ng cm(-2). The levels of nickel on the skin of cashiers, shop assistants, bar staff and hairdressers were below the threshold level for water-soluble ionic nickel for occluded exposure at which 10% of nickel-allergic subjects react (0.01% or 100 parts per million, equivalent to 530 ng cm(-2)) and the five-times higher threshold for unoccluded exposure (500 parts per million). The levels in some nickel platers and nickel refinery workers approached or exceeded these levels. However, few cases of nickel dermatitis are observed in plating and refinery facilities, perhaps due to immune tolerance, self-selection or, for refinery workers, exposure to water-insoluble rather than water-soluble nickel compounds. The elicitation threshold for water-soluble nickel compounds cannot be compared directly with dermal exposure to water-insoluble nickel compounds as the latter release a significantly lesser amount of nickel ions. CONCLUSIONS: We describe a reproducible, simple and rapid procedure for the assessment of nickel levels in occupationally exposed individuals.

Fingers↗
PubMed2006

Which inotrope for which baby?

While we know a lot about blood pressure (BP) responses to various inotropes and a bit about systemic and organ blood flow responses, we know almost nothing about how different inotropes affect clinical outcomes. Low systemic blood flow (SBF) is common in the first 24 h after birth in very preterm babies (and more mature babies with severe respiratory problems) and is not always reflected by low BP. The causes of this low SBF are complex but may relate to maladaptation to high extrauterine systemic (and sometimes pulmonary) vascular resistance. After day 1, hypotensive babies are more likely to have normal or high SBF reflecting vasodilatation. Empirically, inotropes that reduce afterload (such as dobutamine) may be more appropriate in the transitional period, while those with more vasoconstrictor actions (such as dopamine) may be more appropriate later on. Defining the haemodynamic in an individual baby needs both BP and echocardiographic measures of SBF. Research in this area needs to move beyond just demonstrating changes in physiological variables to showing improvements in important clinical outcomes.

Cardiotonic Agents↗
PubMed2005

The PETRRA positron camera: design, characterization and results of a physical evaluation.

The PETRRA positron camera is a large-area (600 mm x 400 mm sensitive area) prototype system that has been developed through a collaboration between the Rutherford Appleton Laboratory and the Institute of Cancer Research/Royal Marsden Hospital. The camera uses novel technology involving the coupling of 10 mm thick barium fluoride scintillating crystals to multi-wire proportional chambers filled with a photosensitive gas. The performance of the camera is reported here and shows that the present system has a 3D spatial resolution of approximately 7.5 mm full-width-half-maximum (FWHM), a timing resolution of approximately 3.5 ns (FWHM), a total coincidence count-rate performance of at least 80-90 kcps and a randoms-corrected sensitivity of approximately 8-10 kcps kBq(-1) ml. For an average concentration of 3 kBq ml(-1) as expected in a patient it is shown that, for the present prototype, approximately 20% of the data would be true events. The count-rate performance is presently limited by the obsolete off-camera read-out electronics and computer system and the sensitivity by the use of thin (10 mm thick) crystals. The prototype camera has limited scatter rejection and no intrinsic shielding and is, therefore, susceptible to high levels of scatter and out-of-field activity when imaging patients. All these factors are being addressed to improve the performance of the camera. The large axial field-of-view of 400 mm makes the camera ideally suited to whole-body PET imaging. We present examples of preliminary clinical images taken with the prototype camera. Overall, the results show the potential for this alternative technology justifying further development.

Equipment Design↗
PubMed2005

In vitro mutation and selection of doubled-haploid Brassica napus lines with improved resistance to Sclerotinia sclerotiorum.

This paper describes a new protocol to develop doubled-haploid (DH) Brassica napus lines with improved resistance to Sclerotinia sclerotiorum. In this protocol, haploid seedlings derived from microspore cultures of B. napus were used to produce haploid calli for in vitro mutation-selection. For routine screening, mutation was induced by EMS (ethylmethane sulfonate) or occurred spontaneously, and screening for resistant mutants occurred on media with added oxalic acid (OA) as a selection agent. In tests with selected lines, the optimal concentration of EMS for mutation was determined to be 0.15%, and the optimal concentration of OA for in vitro screening was 3 mmol/l (half lethal dose was 3.1 mmol/l) for the first cycle of screening. There was an accumulated effect of OA toxicity on calli over two cycles of screening, but the growth and capacity of the surviving calli for regenerating seedlings were not affected by OA. Of the 54 DH lines produced from the in vitro mutation-selection, two DH lines of resistant mutants, named M083 and M004, were selected following seedling and glasshouse tests. The resistance of M083 and M004 to S. sclerotiorum following tests with both mycelial inoculum and OA was greater than that of their donor lines and the resistant control Zhongyou 821. In both glasshouse and field disease nurseries, disease indices on M083 and M004 were less than 50% of those of the control. The time required for M083 and M004 to mature was 14 days and 10 days shorter, respectively, than that of their donor lines. Furthermore, M083 had more pods per inflorescence, a greater 1,000 seed weight and higher yield than its donor line. Random amplified polymorphic DNA characterisation showed that M083 had DNA band patterns that differed from its donor line.

Ascomycota↗
PubMed2004

Calcific myonecrosis: a report of ten new cases with an emphasis on MR imaging.

The aim of this study is to report the typical radiographic and MR imaging features of calcific myonecrosis, which help to distinguish this rare entity from other causes of a calcifying calf mass. Ten patients with a final diagnosis of calcific myonecrosis were referred to a specialist orthopaedic oncology service in a 5-year period with the presumptive diagnosis of malignancy based on recent clinical presentation and imaging findings. Radiographs were available for retrospective review in all ten cases and MR imaging in six. All patients presented with a slow-growing painless calf mass. All gave a history of major trauma to the lower leg many years before, but in only two cases did the referring clinician query whether trauma might be a contributory factor. Radiographs showed well-defined fusiform mineralised masses up to 25 cm in length arising within the calf. The calcification was consistently peripheral and plaque-like. Ossification was not present. MR imaging showed the anterior compartment to be involved in four cases and all compartments in two. T1- and T2-weighted images showed peripheral low signal intensity, more prominent on the T2-weighted images, because of the peripheral mineralization. The contents of the masses were variable on T1-weighted images depending on the differing amounts of blood breakdown products and were heterogeneous on T2-weighted images. The latter may be explained by a combination of the mineralisation and T2 shortening due to blood breakdown products. A gadolinium chelate, administered in two cases, failed to show any appreciable enhancement. Calcific myonecrosis has characteristic clinical, radiographic and MR features that should make the condition easy to recognise. Despite its rarity, it should be included in the differential diagnosis of focal mineralisation of the calf.

Adult↗
PubMed2004

Differential diagnosis of tumours and tumour-like lesions of the infrapatellar (Hoffa's) fat pad: pictorial review with an emphasis on MR imaging.

A variety of intrinsic and extrinsic tumours and tumour-like conditions may affect the infrapatellar (Hoffa's) fat pad (IFP). MR imaging is the technique of choice in evaluating these conditions, but correlation with radiographs is important to identify those lesions producing mineralization. This pictorial review illustrates the spectrum of mass-like lesions that can affect the IFP, emphasizing the radiographic and MR findings that suggest a specific diagnosis.

Bone Neoplasms↗
PubMed2004

Imaging features of intraosseous ganglia: a report of 45 cases.

The aim of this study is to report the spectrum of imaging findings of intraosseous ganglia (IG) with particular emphasis on the radiographic and magnetic resonance (MR) features. Forty-five patients with a final diagnosis of IG were referred to a specialist orthopaedic oncology service with the presumptive diagnosis of either a primary or secondary bone tumour. The diagnosis was established by histology in 25 cases. In the remainder, the imaging features were considered characteristic and the lesion was stable on follow-up radiographic examination. Radiographs were available for retrospective review in all cases and MR imaging in 29. There was a minor male preponderance with a wide adult age range. Three quarters were found in relation to the weight-bearing long bones of the lower limb, particularly round the knee. On radiographs all were juxta-articular and osteolytic; 74% were eccentric in location, 80% had a sclerotic endosteal margin and 60% of cases showed a degree of trabeculation. Periosteal new bone formation and matrix mineralization were not present. Of the 29 cases that underwent MR imaging, 66% were multiloculated. On T1-weighted images the IG contents were isointense or mildly hypointense in 90% cases. Forty-one per cent of the cases showed a slightly hyperintense rim lining that enhanced with a gadolinium chelate. Thirty-eight per cent were associated with soft tissue extension and 17% with a defect of the adjacent articular cortex. Fifty-five per cent showed surrounding marrow oedema on T2-weighted or STIR images and two cases (7%) a fluid-fluid level prior to any surgical intervention. The authors contend that it is semantics to differentiate between an IG and a degenerate subchondral cyst as, while the initial pathogenesis may vary, the histological endpoint is identical, as are the imaging features apart from the degree of associated degenerative joint disease. IGs, particularly when large, may be mistaken for a bone tumour. Correlation of the typical radiographic and MR imaging features will indicate the correct diagnosis and obviate the need for biopsy.

Adult↗
PubMed2004

The MR imaging appearances and natural history of seromas following excision of soft tissue tumours.

Fluid collections (seromas) may accumulate at the site of surgery following excision of musculoskeletal soft tissue tumours. The aim of this retrospective study was to review the magnetic resonance (MR) imaging features of postoperative seromas identifying changes over time on follow-up scans. A total of 170 MR scans from 80 patients were reviewed showing one or more seromas. All patients had undergone previous surgery for a musculoskeletal soft tissue tumour. The typical MR appearances of a seroma were shown to be a well-defined oval or rounded (54%) soft tissue mass, arising at the site of previous surgery, with a thin, dark pseudocapsule, surrounding soft tissue oedema (80%), homogeneous contents that are hypointense (relative to adjacent muscle) on T1-weighted images (74%) and hyperintense on T2-weighted and STIR images (79%). Approximately one-quarter of cases revealed atypical features including hyperintense contents on T1-weighted (26%) and/or heterogeneous contents on T2-weighted images (21%), reflecting the breakdown of blood products and organization of the fluid collection. A distinctive fine feathery pattern arising from the inner surface of the seroma or from septations was identified in 10% of cases. In those patients who underwent one or more follow-up scans, the volume of the seromas decreased in 66% cases, remained unchanged in 15% and increased in 19%. Seromas are not an uncommon finding (<10% of cases) following surgery for a soft tissue tumour. The majority of cases show the typical MR features of a fluid collection. The pitfalls in differentiating an atypical seroma from a recurrent soft tissue sarcoma are discussed.

Adolescent↗
PubMed2004

Early volume expansion for prevention of morbidity and mortality in very preterm infants.

BACKGROUND: Reduced perfusion of organs such as the brain, heart, kidneys and the gastrointestinal tract may lead to acute dysfunction and be associated with permanent injury. Various strategies have been used to provide cardiovascular support to preterm infants including inotropes, corticosteroids and volume expansion. OBJECTIVES: In very preterm infants, does early volume expansion reduce morbidity and mortality. If volume expansion is effective, what type of volume expansion is most effective. SEARCH STRATEGY: The standard search strategy of the Neonatal Review Group was used. See Review Group details for more information. This was supplemented by additional searches of the Oxford Database of Perinatal Trials, and updated search performed of the Cochrane Central Register of Controlled Trials (CENTRAL, Cochrane Library Issue 1, 2004), MEDLINE (1996-January 2004), EMBASE (1980-January 2004), previous reviews including cross references (all articles referenced), abstracts and conferences (Perinatal Society of Australia and New Zealand, and Pediatric Academic Societies and American Academy of Pediatrics meetings 1998-2003). SELECTION CRITERIA: Randomised trials of early volume expansion with normal saline, fresh frozen plasma, albumin, plasma substitutes or blood compared to no treatment or another form of volume expansion in preterm infants < 32 weeks gestation or < 1500g were included. Volume expansion was defined as at least 10 mls/kg given in the first 72 hours of life. DATA COLLECTION AND ANALYSIS: Standard methods of the Neonatal Review Group with use of relative risk (RR), risk difference (RD) and weighted mean difference (WMD). The fixed effects model using RevMan 4.1 was used for meta-analysis. Data from individual studies were only eligible for inclusion if a least 80% of infants were reported for that outcome. MAIN RESULTS: Seven studies were included. Five studies, four with data for mortality, compared volume to no treatment. Most studies enrolled very preterm infants on the basis of gestation or birthweight. Two studies comparing different types of volume expansion enrolled very preterm infants with hypotension. No study enrolled infants on the basis of low blood flow. One study examined the effect of volume expansion on blood flow but in normotensive very preterm infants. Comparing volume and no treatment, 4 studies with a total of 940 very preterm infants reported no significant difference in mortality (RR 1.11, 95% CI 0.88, 1.40). The large NNNI 1996 study reported no significant difference in severe disability (RR 0.80, 95% CI 0.52, 1.23), cerebral palsy (RR 0.76, 95% CI 0.48, 1.20) and combined death or severe disability (RR 1.00, 95% CI 0.80, 1.24). Although one small study (Beverley 1985) reported reduced P/IVH with volume expansion, this was not supported by any other study. No significant difference was reported in grade 3-4 P/IVH and combined death or grade 3-4 P/IVH. One study (NNNI 1996) reported no significant difference in the incidence of hypotension. The finding of decreased necrotising enterocolitis and increased sepsis in infants who received fresh frozen plasma compared to a gelatin-based plasma substitute or no treatment in one study should be treated with caution. No significant differences in mortality or disability were found in this study. Comparing albumin and saline in hypotensive infants, one study (Lynch 2002) reported a significant increase in mean BP and reduced incidence of treatment failure (persistent hypotension). The other study (So 1997) and the meta-analysis of the two studies found no significant difference in treatment failure (RR 0.75, 95% CI 0.53, 1.06) or in any other clinical outcome. REVIEWERS' CONCLUSIONS: There is no evidence from randomised trials to support the routine use of early volume expansion in very preterm infants without cardiovascular compromise. There is insufficient evidence to determine whether infants with cardiovascular compromise benefit from volume expansion. There is insufficient evidence to determine what type of volume expansion should be used in preterm infants (if at all) or for the use of early red cell transfusions. The significance of the finding of a significant increase in blood pressure in hypotensive preterm infants in one trial comparing albumin and saline is unclear, but the overall meta-analyses found no other significant clinical benefit in using albumin compared to saline.

Blood Volume↗
PubMed2004

One-year neurodevelopmental outcome after moderate newborn hypoxic ischaemic encephalopathy.

OBJECTIVES: To define the 1-year neurodevelopmental outcome for survivors of moderate (Sarnat stage 2) neonatal hypoxic-ischaemic encephalopathy (HIE) to facilitate appropriate parental counselling. METHODS: Hospital-based retrospective review of admissions to a tertiary newborn intensive care unit between 1988 and 2000. All babies admitted for seizures were reviewed and those in whom the probable diagnosis was moderate HIE were identified from chart review. Perinatal variables, number of anticonvulsants, duration of hospital stay and 1-year neurodevelopmental outcome was recorded in survivors. RESULTS: Fifty-three babies who survived probable moderate HIE were identified. Forty-two of these were seen at 1 year of age. Of these, 22 (52%) had normal development and neurological examination and four (9.5%) had mild developmental delay with normal neurological examination. Thirteen babies (31%) had cerebral palsy, 11 of whom also had developmental delay. Two infants (5%) who had been severely impaired at 6 months died before 1 year of age. Overall, 36% of survivors of the neonatal period had significant disability and or had died by 1 year of age. Duration of anticonvulsant treatment and length of hospital stay were significantly related to adverse outcome. CONCLUSIONS: These data suggest morbidity rates after moderate HIE in the upper end of the range previously described in the literature. Systematic longer-term follow up of this high-risk group of infants is needed.

Apgar Score↗
PubMed2004

Clinical detection of low upper body blood flow in very premature infants using blood pressure, capillary refill time, and central-peripheral temperature difference.

OBJECTIVE: To determine the accuracy of blood pressure (BP), capillary refill time (CRT), and central-peripheral temperature difference (CPTd) for detecting low upper body blood flow in the first day after birth. METHODS: A prospective, two centre cohort study of 128 infants born at < 30 weeks gestation. Invasive BP (n = 108), CRT (n = 128), and CPTd (n = 46) were performed immediately before echocardiographic measurement of superior vena cava (SVC) flow at three, 5-10, and 24 hours after birth. RESULTS: Forty four (34%) infants had low SVC flow (< 41 ml/kg/min) in the first day, 13/122 (11%) at three hours, 39/126 (31%) at 5-10 hours, and 4/119 (3%) at 24 hours. CPTd did not detect infants with low flows. Combining all observations in the first 24 hours, CRT > or = 3 seconds had 55% sensitivity and 81% specificity, mean BP < 30 mm Hg had 59% sensitivity and 77% specificity, and systolic BP < 40 mm Hg had 76% sensitivity and 68% specificity for detecting low SVC flow. Combining a mean BP < 30 mm Hg and/or central CRT > or = 3 seconds increases the sensitivity to 78%. CONCLUSIONS: Low upper body blood flow is common in the first day after birth and strongly associated with peri/intraventricular haemorrhage. BP and CRT are imperfect bedside tests for detecting low blood flow in the first day after birth.

Area Under Curve↗
PubMed2004

Managing the cost of cardiovascular prevention in primary care.

Prescribing costs for the prevention of cardiovascular disease are rising nationally, particularly in relation to implementation of the National Service Framework for coronary heart disease. Prescribing effective treatment that is going to benefit the patient's overall management--evidence based medicine--is the key to funding drugs for cardiovascular prevention. It is clear that there is a lot of waste within the system. If the current waste in prescribing can be reduced, it should be possible to fund new developments, not only in cardiovascular disease but also in other therapeutic areas.

Cardiovascular Diseases↗
PubMed2003

MR imaging in the assessment of residual tumour following inadequate primary excision of soft tissue sarcomas.

The purpose of this retrospective study was twofold: firstly, to assess the ability of MR imaging in confirming/excluding the presence of residual tumour following inadequate primary excision of soft tissue sarcomas; and secondly, to assess the accuracy of the original radiologists report as compared with a retrospective review of the scan hard copy in confirming/excluding. A total of 111 cases were identified that fulfilled the inclusion criteria of inadequate primary surgery followed by a MR scan and subsequent wide re-excision of the surgical field. The gold standard for the assessment of the MR imaging studies was histological examination of the re-excision specimens. Histological examination revealed residual tumour in 63 (56.7%) cases. In 48 cases the residual tumour was classified macroscopic (maximum diameter >10 mm) and 15 cases microscopic (maximum diameter </=10 mm). The original radiologists reports failed to indicate the presence or absence of tumour in 7 (6.3%) cases. In the remaining 104 cases the diagnostic performance of MR imaging gave a sensitivity of 0.64, specificity of 0.93, positive predictive value of 0.93 and negative predictive value of 0.67. In 12 of the 21 false-negative scans the residual tumour was microscopic. Subjective assessment of the radiologist's reports indicated that the proportion of equivocal reports was much higher in both the false-negative and false-positive groups as compared with the true groups. An unblinded retrospective review of the scan hard copies only differed from the original radiologists report in 8 (7.2%) cases. Contrast-enhanced sequences were not routinely obtained in this series. The results suggest that the poor negative predictive value can be attributed more to limitations of the MR scan and not to failures in observation or interpretation by the radiologists. Despite the low negative predictive value, MR imaging remains useful in planning the re-excision surgery by identifying the site and extent of the original operation and size of major residual tumour.

Adolescent↗
PubMed2003

Transvenous cardioversion--a novel asymmetric rectangular biphasic waveform from a radiofrequency defibrillator compared with conventional waveforms in atrial fibrillation.

BACKGROUND: We investigated a novel device that delivered biphasic and monophasic shocks without tilt, in transvenous cardioversion of atrial fibrillation (AF). The device contains a radiofrequency (RF) transmitting primary, a 15mm air gap and a passive secondary unit that produces the required direct current waveform. METHODS: The device was assessed in 10 anaesthetised and ventilated sheep (65 +/- SD 12kg). Defibrillation leads were positioned in the distal coronary sinus and the lateral right atrium. The novel RF defibrillator was assessed using rectangular monophasic or biphasic pulses and compared to conventional (C) tilted waveforms (Ventritex HVS-02). During AF placebo shocks were delivered to a 50 Omega dummy load. Sustained AF was induced by rapid atrial pacing and 5 attempts at cardioversion were made for each waveform. Success was defined as reversion to sinus rhythm within 5 beats of shock delivery. RESULTS: No arrhythmic complications were observed for the 400 shocks delivered. CONCLUSION: A reduction in phase 2 voltage does not affect the efficacy of rectangular waveforms but does facilitate energy reduction. Asymmetric rectangular biphasic waveforms with phase 2 voltage at 50% of phase 1 are more efficacious than equivalent voltage conventional waveforms for transvenous cardioversion of AF. The novel defibrillator is safe and effective. Design modifications will enable this device to be used as an implantable defibrillator with an external RF power source.

Animals↗
PubMed2003

Differential nicotinic acetylcholine receptor subunit expression in the human hippocampus.

Neuronal nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels composed of alpha and beta subunits with specific structural, functional and pharmacological properties. In this study the distribution of alpha3, alpha4, alpha7, beta2 and beta4 nAChR subunits in the human hippocampus was investigated using immunohistochemistry. Most pyramidal neurons, pre-alpha cells of the entorhinal cortex and dentate granule cells were immunoreactive for all subunits. Small islands of alpha7 immunoreactive cells were present in the outer presubiculum. alpha4 and beta2, and alpha3, alpha4 and beta2 immunoreactive fibre tracts were present in the stratum radiatum and subiculum, respectively, suggesting nAChRs may play a role in modulating inputs to the hippocampus via Schaffer collaterals and along the perforant pathway. Some astrocytes were immunoreactive for alpha3, alpha7 and beta4 subunits. Immunoreactivity to all subunits was noted in association with blood vessels. These results indicate the involvement of multiple nAChR subtypes in the modulation of both neuronal and non-neuronal functions in the human hippocampus.

Adult↗