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P J Allen

Publications and source records attributed to P J Allen.

At least 19 recordsLinked to original sources
PubMed2001

Immunohistochemical analysis of sentinel lymph nodes from patients with Merkel cell carcinoma.

BACKGROUND: Immunohistochemical analysis of sentinel lymph nodes from patients with breast carcinoma and melanoma has been shown to increase the sensitivity for detecting lymph node metastases. To the authors' knowledge, this technique has not been described in patients with Merkel cell carcinoma. METHODS: Lymphatic mapping and sentinel lymph node biopsy was performed on 26 patients with Merkel cell carcinoma between 1997 and 1999. All sentinel lymph nodes were analyzed with conventional hematoxylin and eosin (H&E) staining and then analyzed with immunohistochemical staining to evaluate whether this additional technique would increase the number of patients found to have lymph node metastasis. RESULTS: The median age of the patients in the current study was 67 years and the median tumor size at the time of presentation was 2 cm. Lymph node metastases were identified in 5 of the 26 patients (19%). Three of these five lymph node positive patients were identified with H&E staining. The remaining two patients were identified only after immunohistochemical analysis. The median follow-up in this group of lymph node positive patients was 14 months, with 2 of the 5 lymph node positive patients developing a recurrence. The median follow-up in the 21 patients who were lymph node negative was 19 months, with only 1 patient having developed a recurrence at the time of last follow-up. CONCLUSIONS: Immunohistochemical analysis of sentinel lymph nodes from patients with Merkel cell carcinoma appears to increase the sensitivity of detecting clinically occult lymph node metastases.

Adult↗
PubMed2001

Polymyography combined with time-locked video recording (video EMG) for presurgical assessment of patients with cervical dystonia.

We assessed 26 patients with cervical dystonia, in whom botulinum toxin (BT) injections had failed, before selective peripheral denervation. We decided to base the decision which muscle should be denervated on both clinical information and EMG data and focussed on the following features: activity at onset or during 'dystonic spasms' (according to the concept of the 'leading' dystonic muscle), paradoxical activity during voluntary head movements causing restriction of head movements opposite the side of head turn or tilt and activity when symptoms deteriorated during walking. To identify these muscles we developed a new recording system that integrates simultaneous video-taping and polymyography (video EMG) by means of a digital counter, driven by the recording software (resolution 0.1 s), that was fixed in view of the video camera. This system time-locked clinical signs with relevant EMG activity thus allowing demonstration of the above features. These were found in 68% of dystonic muscles with each of them being present in approximately 40%. Video EMG allows an integrated approach to identify overactive neck muscles in patients with cervical dystonia taking into account both relevant clinical findings and EMG data.

Adult↗
PubMed2000

EEG recording during fMRI experiments: image quality.

Electroencephalographic (EEG) monitoring during functional magnetic resonance imaging (fMRI) experiments is increasingly applied for studying physiological and pathological brain function. However, the quality of the fMRI data can be significantly compromised by the EEG recording due to the magnetic susceptibility of the EEG electrode assemblies and electromagnetic noise emitted by the EEG recording equipment. We therefore investigated the effect of individual components of the EEG recording equipment on the quality of echo planar images. The artifact associated with each component was measured and compared to the minimum scalp-cortex distance measured in normal controls. The image noise originating from the EEG recording equipment was identified as coherent noise and could be eliminated by appropriate shielding of the EEG equipment. It was concluded that concurrent EEG and fMRI could be performed without compromising the image quality significantly if suitable equipment is used. The methods described and the results of this study should be useful to other researchers as a framework for testing of their own equipment and for the selection of appropriate equipment for EEG recording inside a MR scanner.

Adolescent↗
PubMed2000

Identification of intervals on chromosomes 1, 3, and 13 linked to the development of lupus in BXSB mice.

OBJECTIVE: To identify intervals containing systemic lupus erythematosus (SLE) susceptibility alleles in the BXSB strain of mice. METHODS: We analyzed 286 (B10 x [B10 x BXSB]F1) backcross mice for a range of phenotypic traits associated with the development of SLE in BXSB mice. The mice were genotyped using 93 microsatellite markers, and the linkage of these markers to disease was studied by extreme-phenotype and quantitative trait locus analysis. RESULTS: The disease phenotype in these backcross mice was less severe than that in BXSB mice. However, antinuclear antibody production was increased compared with the parental strain. We identified 4 areas of genetic linkage to disease on chromosome 1 (Bxs1-4), 1 on chromosome 3 (Bxs5), and another interval on chromosome 13 which were associated with various aspects of the phenotype. Bxs4 and Bxs5 are located in regions not previously linked to disease in other models of SLE. CONCLUSION: SLE in the BXSB mouse model has a complex genetic basis and involves at least 5 distinct intervals located on chromosomes 1 and 3. There is evidence that different intervals affect particular aspects of the SLE phenotype.

Alleles↗
PubMed2000

A method for removing imaging artifact from continuous EEG recorded during functional MRI.

Combined EEG/fMRI recording has been used to localize the generators of EEG events and to identify subject state in cognitive studies and is of increasing interest. However, the large EEG artifacts induced during fMRI have precluded simultaneous EEG and fMRI recording, restricting study design. Removing this artifact is difficult, as it normally exceeds EEG significantly and contains components in the EEG frequency range. We have developed a recording system and an artifact reduction method that reduce this artifact effectively. The recording system has large dynamic range to capture both low-amplitude EEG and large imaging artifact without distortion (resolution 2 microV, range 33.3 mV), 5-kHz sampling, and low-pass filtering prior to the main gain stage. Imaging artifact is reduced by subtracting an averaged artifact waveform, followed by adaptive noise cancellation to reduce any residual artifact. This method was validated in recordings from five subjects using periodic and continuous fMRI sequences. Spectral analysis revealed differences of only 10 to 18% between EEG recorded in the scanner without fMRI and the corrected EEG. Ninety-nine percent of spike waves (median 74 microV) added to the recordings were identified in the corrected EEG compared to 12% in the uncorrected EEG. The median noise after artifact reduction was 8 microV. All these measures indicate that most of the artifact was removed, with minimal EEG distortion. Using this recording system and artifact reduction method, we have demonstrated that simultaneous EEG/fMRI studies are for the first time possible, extending the scope of EEG/fMRI studies considerably.

Adult↗
PubMed2000

Effects of front and dual suspension mountain bike systems on uphill cycling performance.

PURPOSE: The purpose of this study was to evaluate the effects of front suspension (FS) and dual suspension (DS) mountain bike designs on time-trial performance and physiological responses during uphill cycling on a paved- and off-road course. METHODS: Six trained male cyclists (35.6 +/- 9 yr, 76.9 +/- 8.8 kg, VO2 peak 58.4 +/- 5.6 mL x kg(-1) x min-1)) were timed using both suspension systems on an uphill paved course (1.62 km, 183-m elevation gain) and an uphill off-road course (1.38 km, 123-m elevation gain). During the field trials, VO2 was monitored continuously with a KB1-C portable gas analyzer, and power output with an SRM training system. RESULTS: On the paved course, total ride time on FS (10.4 +/- 0.7 min) and DS (10.4 +/- 0.8 min) was not different (P > 0.05). Similarly, total ride time on the off-road course was not significantly different on the FS bike (8.3 +/- 0.7 min) versus the DS bike (8.4 +/- 1.1 min). For each of the course conditions, there was no significant difference between FS and DS in average minute-by-minute VO2, whether expressed in absolute (ABS; L x min(-1)) or relative (REL; mL x [kg body wt +/- kg bike wt(-1)] x min(-1) values. Average power output (W) was significantly lower for ABS FS versus DS (266.1 +/- 61.6 W vs 341.9 +/- 61.1 W, P < 0.001) and REL FS versus DS (2.90 +/- 0.55 W x kg(-1) vs 3.65 +/- 0.53 W x kg(-1), P < 0.001) during the off-road trials. Power output on the paved course was also significantly different for ABS FS versus DS (266.6 +/- 52 W vs 345.4 +/- 53.4 W, P < 0.001) and REL FS versus DS (2.99 +/- 0.55 W x kg(-1) vs 3.84 +/- 0.54 W x kg(-1), P < 0.001). CONCLUSION: We conclude that despite significant differences in power output between FS and DS mountain bike systems during uphill cycling, these differences do not translate into significant differences in oxygen cost or time to complete either a paved- or off-road course.

Adult↗
PubMed2000

Design of an intensive epilepsy monitoring unit.

Video-electroencephalography (EEG) telemetry is a crucial component in the comprehensive evaluation of patients with epilepsy. The reasons for patients needing to be monitored fall broadly into three groups: presurgical assessment (36% of our patients), diagnostic assessment (52%), and sleep disorders (12%). Video EEG can be used to differentiate unusual epilepsies from pseudo seizures or other causes of paroxysmal neurological events. The design of a unit depends on the case mix of patients expected to be referred. The key elements to a successful unit are a reliable, flexible, easy-to-use recording system and a team of dedicated, experienced staff, both nursing and technical. The unit at the National Hospital is a six-bed ward with 7 nurses to provide 24-hour coverage, 5 technicians working in shifts, and physics support. A minimum of two staff are on duty at all times. It operates on a five-day week with a throughput of approximately 500 patients per year. It is vital that investigations are performed as efficiently and effectively as possible, and the patient's safety and wellbeing is paramount at all times. Drug reduction is likely to be used to precipitate seizures, especially in those being considered for epilepsy surgery, and this poses a risk of provoked secondary generalized seizures. Continuous supervision of patients, and the ability to respond rapidly to a seizure, are therefore essential. We adopt a standardized easy-to-follow drug-reduction protocol, similar to that used by other centers.

Anticonvulsants↗
PubMed1999

Desmoid tumors of the chest wall.

Desmoid tumors are rare soft tissue neoplasms derived from fascial or musculoaponeurotic structures. These tumors are histologically benign but may behave aggressively at the local level with multiple recurrences after complete resection being common. Chest wall desmoids account for approximately 20% of all patients with desmoid tumors. Patients with these lesions are often asymptomatic and thus commonly present with lesions greater than 10 cm in size. The treatment for these neoplasms remains margin negative surgical excision, and, given the often large size at presentation, may require extensive chest wall resection. When this is required, chest wall reconstruction with either prosthetic material and/or autologous tissue may be performed. There may be recurrence in as many as 75% of patients. Neither adjuvant radiotherapy or chemotherapy have been shown to reduce the rate of recurrence. Recurrence should also be treated with surgical resection because patients who undergo complete surgical resection of recurrence are as likely to remain disease free after resection as patients who present with primary disease.

Biopsy↗
PubMed1999

Where have all the fathers gone? An extensive microsatellite analysis of paternity in the grey seal (Halichoerus grypus).

Microsatellites were used to conduct an extensive analysis of paternity of grey seals from two Scottish breeding colonies at North Rona (n = 1189) and the Isle of May (n = 694), spanning more than a decade. A maximum of 46% of pups at North Rona and 29% of pups at the Isle of May could be allocated a father, even though the majority of candidate males for specific study sites within each colony were believed to have been sampled. Based on the paternities which could be assigned, both colonies showed evidence of reproductive skew, apparently due to the presence of approximately five males who were exceptionally successful. Some males were assigned paternities at least 10 years before, and colleagues 10 years after, being sampled, implying a reproductive lifespan of at least 10 years, and there are indications that the real maximum lies in the range 15-20 years. Male grey seals appear to have at least two breeding strategies they can adopt. On land, some males benefit from a traditionally polygynous system. However, between 50 and 70% of grey seal pups born at a particular colony are not fathered by males who are likely to be sampled by us, implying that these males seldom venture ashore here. We conclude that aquatic mating may play a much larger role in the grey seal than has previously been thought.

Animals↗
PubMed1999

Reproducible localization of interictal epileptiform discharges using EEG-triggered fMRI.

We report preliminary experiences using fMRI triggered by EEG to localize the site of interictal epileptiform activity. EEG was recorded in the scanner and monitored on-line; the recording quality was good enough to allow the clear identification of spikes in the EEG. Snap-shot EPI was performed 2-4 s after an epileptiform discharge ('spike') or after at least 10 s of background activity ('rest') was observed. A pixel-by-pixel t-test was performed between the 'rest' and the 'spike' images to determine areas of significant activation. Significant activation was obtained in a patient with epilepsy. To assess the reliability and reproducibility of the technique, the patient was scanned on four separate occasions with similar areas being activated in all the studies, confirming the validity of the result.

Brain↗
PubMed1999

EEG-triggered functional MRI of interictal epileptiform activity in patients with partial seizures.

EEG-triggered functional MRI (fMRI) offers the potential to localize the generators of scalp EEG events, such as interictal epileptiform discharges, using a biological measurement as opposed to relying solely on modelling techniques. Although recent studies have demonstrated these possibilities in a small number of patients, wider application has been limited by concerns about patient safety, severe problems due to pulse-related artefact obscuring the EEG trace, and lack of reproducibility data. We have systematically studied and resolved the issues of patient safety and pulse artefact and now report the application of the technique in 24 experiments in 10 consecutive patients with localization-related epilepsy and frequent interictal epileptiform discharges (spikes or spike wave). At least two experiments were performed for each patient. In each experiment, 10- or 20-slice snapshot gradient-echo planar images were acquired approximately 3.5 s after a single typical epileptiform discharge (activation image) and in the absence of discharges (control image). Between 21 and 50 epileptiform discharges were sampled in each experiment. The significance of functional activation was tested using the t test at 95% confidence on a pixel-by-pixel basis. Six of the 10 patients showed reproducible focal changes of the blood oxygen level-dependent (BOLD) signal, which occurred in close spatial relationship to the maximum of the epileptiform discharges in the concurrent EEG. No reproducible focal BOLD signal changes were observed in the remaining four patients. In conclusion, EEG-triggered fMRI is now a sufficiently developed technique to be more widely used in clinical studies, demonstrating that it can reproducibly localize the brain areas involved in the generation of spikes and spike wave in epilepsy patients with frequent interictal discharges.

Adult↗
PubMed1999

Surgical management of Merkel cell carcinoma.

OBJECTIVES: To characterize the natural history of Merkel cell carcinoma (MCC) and to analyze the influence of patient, tumor, and treatment-related variables on survival and recurrence. SUMMARY BACKGROUND DATA: Approximately 425 cases of MCC have been described in the literature. This study represents the largest experience reported. METHODS: A review was performed of patients who had been treated at Memorial Sloan-Kettering Cancer Center for MCC between 1969 and 1996. Follow-up data were available for 102 of the 109 (94%) patients identified. RESULTS: The overall 5-year disease-specific survival rate was 74%. The median follow-up was 35 months. For all patients, the only independent predictor of survival was the tumor stage at presentation. For patients with stage I disease, the tumor size at presentation was also an independent predictor of survival. Recurrence of disease occurred in 55 patients (55%), and the most common site of first recurrence was within the draining lymph nodes (n = 35). Elective lymph node dissection was the only parameter independently predictive of improved relapse-free survival. The overall disease-specific survival rate after recurrence was 62%. Predictors of improved disease-specific survival after recurrence included nodal as compared to local or distant recurrence, the ability to render the patient free of disease after recurrence, and a disease-free interval of >8 months. CONCLUSION: The prognosis for patients with MCC is favorable, and even after recurrence the majority of patients experience long-term survival. Incorporation of size into the staging system more accurately predicts survival in patients with stage I disease. Although elective lymph node dissection decreased the rate of recurrence, it was not associated with improved overall survival.

Adult↗
PubMed1999

Multimodal MR imaging: functional, diffusion tensor, and chemical shift imaging in a patient with localization-related epilepsy.

PURPOSE: To demonstrate the integration of complementary functional and structural data acquired with magnetic resonance imaging (MRI) in a patient with localization-related epilepsy. METHODS: We studied a patient with partial and secondarily generalized seizures and a hemiparesis due to a malformation of cortical development (MCD) in the right hemisphere by using EEG-triggered functional MRI (fMRI), diffusion tensor imaging (DTI), and chemical shift imaging (CSI). RESULTS: fMRI revealed significant changes in regional blood oxygenation associated with interictal epileptiform discharges within the MCD. DTI showed a heterogeneous microstructure of the MCD with reduced fractional anisotropy, a high mean diffusivity, and displacement of myelinated tracts. CSI demonstrated low N-acetyl aspartate (NAA) concentrations in parts of the MCD. CONCLUSIONS: The applied MR methods described functional, microstructural, and biochemical characteristics of the epileptogenic tissue that cannot be obtained with other noninvasive means and thus improve the understanding of the pathophysiology of epilepsy.

Adult↗
PubMed1998

Multiple lupus susceptibility loci map to chromosome 1 in BXSB mice.

BXSB mice spontaneously develop a lupus-like syndrome that is accelerated by the Yaa gene (Y-linked autoimmune accelerator). We studied the phenotype of disease in (B10 x BXSB)F1 and (BXSB x (B10 x BXSB)F1) backcross mice and genotyped 224 backcross animals to allow a microsatellite-based genome-wide linkage analysis to be conducted. In the backcross population, three intervals on chromosome 1 showed significant linkage to disease, suggesting that multiple loci contribute to the production of autoimmune disease. D1Mit5 at 32.8 cM was linked to development of nephritis (chi(2) = 15.68, p = 7.5 x 10(-5)), as was D1Mit12 at 63.1 cM (chi(2) = 20.17, p = 7.1 x 10(-6)). D1Mit403 at 100 cM was linked to anti-dsDNA Ab production (chi(2) = 17.28, p = 3.2 x 10(-5)). Suggestive linkages to antinuclear Abs and nephritis were identified on chromosome 3, to splenomegaly on chromosome 4, and to anti-ssDNA Ab production on chromosome 10. Chromosome 4 and the telomeric region of chromosome 1 have previously been linked to disease in other mouse models of systemic lupus erythematosus; however, the centromeric regions of chromosome 1 and chromosomes 3 and 10 are unique to BXSB. This implies that, though some loci may be common to a number of mouse models of lupus, different clusters of disease genes confer disease susceptibility in different strains of mice.

Animals↗
PubMed1998

The effects of hepatic cryosurgery on tumor growth in the liver.

BACKGROUND: The effects of hepatic cryosurgery on residual hepatic tumor growth, and on tumor immunity, have not been determined. MATERIALS AND METHODS: Two experiments were performed. In both, animals (n = 10 per group) had solitary left lobe hepatomas established, and underwent left lobectomy, cryoablation, or control laparotomy. Experiment I: immediately after tumor treatment, intraportal challenge of hepatoma cells was performed to evaluate for the effects of treatment on residual hepatic tumor growth. Experiment II: animals were challenged 14 days after tumor treatment, and splenocyte cytotoxicity assays were performed to evaluate for tumor immunity. Hepatic tumor nodules were counted 3 weeks after challenge in both experiments. RESULTS: In animals challenged immediately after tumor treatment, the mean number of liver nodules at 3 weeks was similar between control and cryoablation groups (65 +/- 13 vs 115 +/- 38, P = 0.17). Animals that had undergone resection, however, had a significant increase in the mean number of nodules as compared to cryoablation (278 +/- 74 vs 115 +/- 38, P = 0. 04) and control (278 +/- 74 vs 65 +/- 13, P = 0.002) animals. In addition, only resection animals had elevation in serum levels of the growth factor FGF-basic, 48 h after treatment (mean = 30 +/- 14 pg/ml). In animals challenged 14 days following treatment, all groups had similar numbers of nodules (resection vs cryoablation, P = 0.8). Splenocyte cytotoxicity was not increased after cryosurgical treatment. CONCLUSIONS: Unlike partial hepatectomy, cryoablation of hepatomas in rats does not accelerate residual tumor growth in the liver or result in production of the growth factor FGF-basic. We did not find evidence for the development of tumor immunity following cryosurgery.

Alanine Transaminase↗
PubMed1998

Identification of EEG events in the MR scanner: the problem of pulse artifact and a method for its subtraction.

Triggering functional MRI (fMRI) image acquisition immediately after an EEG event can provide information on the location of the event generator. However, EEG artifact associated with pulsatile blood flow in a subject inside the scanner may obscure EEG events. This pulse artifact (PA) has been widely recognized as a significant problem, although its characteristics are unpredictable. We have investigated the amplitude, distribution on the scalp, and frequency of occurrence of this artifact. This showed large interindividual variations in amplitude, although PA is normally largest in the frontal region. In five of six subjects, PA was greater than 50 microV in at least one of the temporal, parasagittal, and central channels analyzed. Therefore, we developed and validated a method for removing PA. This subtracts an averaged PA waveform calculated for each electrode during the previous 10 s. Particular attention has been given to reliable ECG peak detection and ensuring that the average PA waveform is free of other EEG artifacts. Comparison of frequency spectra for EEG recorded outside and inside the scanner, with and without PA subtraction, showed a clear reduction in artifact after PA subtraction for all four frequency ranges analyzed. As further validation, lateralized epileptiform spikes were added to recordings from inside and outside the scanner: PA subtraction significantly increased the proportion of these spikes that were correctly identified and decreased the number of false spike detections. We conclude that in some subjects, EEG/fMRI studies will be feasible only using PA subtraction.

Adult↗