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Biomedical subjects

J R Anderson

Publications and source records attributed to J R Anderson.

At least 73 records · Page 4Linked to original sources
PubMed2000

Comparison of voxel- and volume-of-interest-based analyses in FDG PET scans of HIV positive and healthy individuals.

UNLABELLED: Abnormal glucose metabolic patterns in the brain have been reported for HIV-1 seropositive (HIV+) patients when compared with seronegative healthy individuals. The metabolic covariance pattern obtained from voxel- or volume-of-interest (VOI)-based multivariate data analysis techniques can be used to characterize disease and potentially to detect and monitor disease progression in the early stage of AIDS dementia complex. However, the arbitrary smoothing typically applied to PET data during reconstruction and processing to reduce noise has an unknown effect on the data, especially for the voxel-based analysis. METHODS: To investigate the impact of smoothing on a discrimination task, we applied principal component analysis with scaled subprofile-model preprocessing (SSM/PCA) followed by Fisher discriminant analysis to FDG PET data that were reconstructed and processed with different degrees of smoothing. Receiver operating characteristic curves were used to compare the ability of derived metabolic covariance patterns to discriminate HIV+ patients from healthy volunteers. RESULTS: For the voxel-based analysis, we found that the spatial distribution of voxel weights from the SSM/PCA analysis suggested edge effects along major tissue and cerebrospinal fluid boundaries, indicative of a disease-specific pattern of cerebral atrophy for the HIV+ patients. In terms of its discrimination performance, this metabolic covariance pattern is stable and insensitive to a wide range of smoothing kernels, except for ramp reconstruction and Hanning reconstruction with 7 x 7 x 7 block smoothing. In these reconstructions, the discrimination performance decreased as a result of high image noise and excessive smoothing, respectively. Our results also indicated that if sufficient variance from the VOI measurements is included, the overall performance of a conventional VOI-based analysis can be similar to that of the voxel-based analysis for the same discrimination task. However, the VOI-based analysis performed poorly at low false-positive fraction and is less tolerant to noise in the metabolic covariance pattern than the voxel-based analysis. CONCLUSION: We have obtained a unique covariance pattern of brain glucose metabolism for HIV+ patients compared with healthy volunteers. Discrimination based on this covariance pattern was found to be insensitive to a wide range of image smoothness.

AIDS Dementia Complex↗
PubMed2000

Strengthening HIV prevention: application of a research-to-practice framework.

As the HIV epidemic continues to affect at-risk and vulnerable populations, providers strive to improve prevention programs, in part by seeking new interventions with greater effects. Although interventions with scientific evidence of effectiveness are vital to this effort, many challenges limit access to research products. We examine key challenges and offer a framework for moving research to practice, one in which research steps are linked to practice steps and all these activities take place in a complex and dynamic environment. The Replicating Effective Programs (REP) project of the Centers for Disease Control and Prevention and other technology transfer activities illustrate the operation of this framework for HIV prevention. Further actions to improve technology transfer are called for. These include reducing time from study design to practice; learning from field-based implementations; providing guidance about fidelity to, and tailoring of, science-based interventions; improving linkages among consumers, providers, and researchers; and seeking additional resources.

Centers for Disease Control and Prevention, U.S.↗
PubMed1999

Reproducibility of BOLD-based functional MRI obtained at 4 T.

The reproducibility of activation patterns in the whole brain obtained by functional magnetic resonance imaging (fMRI) experiments at 4 Tesla was studied with a simple finger-opposition task. Six subjects performed three runs in one session, and each run was analyzed separately with the t-test as a univariate method and Fisher's linear discriminant analysis as a multivariate method. Detrending with a first- and third-order polynomial as well as logarithmic transformation as preprocessing steps for the t-test were tested for their impact on reproducibility. Reproducibility across the whole brain was studied by using scatter plots of statistical values and calculating the correlation coefficient between pairs of activation maps. In order to compare reproducibility of "activated" voxels across runs, subjects and models, 2% of all voxels in the brain with the highest statistical values were classified as activated. The analysis of reproducible activated voxels was performed for the whole brain and within regions of interest. We found considerable variability in reproducibility across subjects, regions of interest, and analysis methods. The t-test on the linear detrended data yielded better reproducibility than Fisher's linear discriminant analysis, and therefore seems to be a robust although conservative method. Preliminary data indicate that these modeling results may be reversed by preprocessing to reduce respiratory and cardiac physiological noise effects. The reproducibility of both the position and number of activated voxels in the sensorimotor cortex was highest, while that of the supplementary motor area was much lower, with reproducibility of the cerebellum falling in between the other two areas.

Adult↗
PubMed1999

Are brain functions really additive?

Although Positron Emission Tomography (PET) and functional magnetic resonance imaging (fMRI) studies commonly subtract data obtained during two or more experimental conditions to decompose a complex task, there have been few opportunities to evaluate this approach directly. In the present study, PET was used to study three motor speech tasks selected such that two were constituent components of the third, making possible a direct examination of decomposition by subtraction. In Experiment 1, a group of 13 right-handed normal volunteers participated in three activation studies: syllable repetition; phonation; and repetitive lip closure. A scanning session was devoted to a single task, repeated four times. In Experiment 2, six of the original subjects performed the same three activation studies during a single scanning session. Whether tasks were studied in separate scanning sessions or combined within a single session, the results of decomposition by compound subtraction differed significantly from the results obtained when individual tasks were compared to a simple baseline condition. These data failed to demonstrate task additivity, a necessary property if decomposition by subtraction is to provide an accurate characterization of the brain activity accompanying complex behavior.

Adult↗
PubMed1999

Plurality and resemblance in fMRI data analysis.

We apply nine analytic methods employed currently in imaging neuroscience to simulated and actual BOLD fMRI signals and compare their performances under each signal type. Starting with baseline time series generated by a resting subject during a null hypothesis study, we compare method performance with embedded focal activity in these series of three different types whose magnitudes and time courses are simple, convolved with spatially varying hemodynamic responses, and highly spatially interactive. We then apply these same nine methods to BOLD fMRI time series from contralateral primary motor cortex and ipsilateral cerebellum collected during a sequential finger opposition study. Paired comparisons of results across methods include a voxel-specific concordance correlation coefficient for reproducibility and a resemblance measure that accommodates spatial autocorrelation of differences in activity surfaces. Receiver-operating characteristic curves show considerable model differences in ranges less than 10% significance level (false positives) and greater than 80% power (true positives). Concordance and resemblance measures reveal significant differences between activity surfaces in both data sets. These measures can assist researchers by identifying groups of models producing similar and dissimilar results, and thereby help to validate, consolidate, and simplify reports of statistical findings. A pluralistic strategy for fMRI data analysis can uncover invariant and highly interactive relationships between local activity foci and serve as a basis for further discovery of organizational principles of the brain. Results also suggest that a pluralistic empirical strategy coupled formally with substantive prior knowledge can help to uncover new brain-behavior relationships that may remain hidden if only a single method is employed.

Brain↗
PubMed1999

Progress in the surgical management of vaginal rhabdomyosarcoma: a 25-year review from the Intergroup Rhabdomyosarcoma Study Group.

BACKGROUND/PURPOSE: During its 25 years of experience, the Intergroup Rhabdomyosarcoma Study Group (IRSG) has completed four sequential prospective clinical trials to improve survival and decrease morbidity rates in childhood rhabdomyosarcoma (RMS). Surgical management of vaginal RMS has changed dramatically. METHODS: The records of 72 patients with localized vaginal RMS were reviewed to assess surgical therapy, chemotherapy, and radiotherapy and their relation to outcome. RESULTS: Each successive IRSG trial resulted in decreased need for surgical resection (IRS-I, 100%; IRS-II, 70%; IRS-III, 30%; IRS-IV, 13%) and excellent disease-free survival using increasingly effective multiagent chemotherapy. CONCLUSIONS: Primary chemotherapy after initial biopsy provides excellent tumor control. Local resection may be appropriate, but removal of organs (ie, complete vaginectomy/hysterectomy) has no role except in persistent or recurrent disease. Mature, residual rhabdomyoblasts may be evidence of a chemotherapy response, and further surveillance and biopsy without surgical resection is adequate treatment.

Algorithms↗
PubMed1999

Does debulking improve survival rate in advanced-stage retroperitoneal embryonal rhabdomyosarcoma?

UNLABELLED: BACKGROUND, METHODS, AND PURPOSE: The authors examined demographic and clinical features, therapy, and outcome of patients with advanced (group III or IV) rhabdomyosarcoma (RMS) of the retroperitoneum and nongenitourinary pelvis treated in the Intergroup Rhabdomyosarcoma Study Group (IRSG) III (1984 to 1991, n = 41) or IV pilot (1987 to 1991, n = 53) studies to assess the role of initial debulking surgery. RESULTS: Ninety-four patients with retroperitoneal primary tumors and gross locoregional residual tumor (group III, n = 53) or metastatic disease (group IV tumors, n = 41) were treated with combination chemotherapy (ie, vincristine, dactinomycin, and cyclophosphamide with or without other agents plus radiation therapy, RT) after biopsy only or subtotal resection. These retroperitoneal tumors usually were invasive (T2, 76%). Most patients were younger than 10 years of age (n = 69, 73%), the male to female ratio was 1.4, and tumors usually were embryonal (n = 64, 68%). Overall 4-year failure-free survival (FFS) was 50%; survival was 60%. Survival rate was better for girls (4-year survival rate, 75% v49% for boys; P = .05) and was not significantly different for patients treated in IRS-III (66%) or IRS-IV pilot (52%). However, it was better for patients with embryonal versus alveolar or undifferentiated tumors (4-year survival rate, 70% v 42%; P = .002). In adolescents, RMS is different from that seen in children less than 10 years old; most cases are alveolar or undifferentiated (16 of 29, 55%). Surgery for most (21 of 24) patients with alveolar tumors comprised biopsy only. By contrast, of 64 patients with embryonal tumors, 39 (61%) underwent biopsy only, whereas 25 (39%) had debulking surgery. Patients whose tumors were debulked fared better than those whose tumors underwent biopsy only (4-year FFS rate, 72% v48%; P = 0.03). Patients with group IV embryonal tumors fared unexpectedly better than those with group IV alveolar or undifferentiated tumors (70% versus 42% 4-year survival rate, P < .05), and patients less than 10 years of age with group IV embryonal tumors had 4-year survival rate of 77%, indicating the importance of the biology of these tumors. CONCLUSIONS: Multimodal therapy, including multiagent chemotherapy plus RT, appears to improve survival rate in patients with advanced embryonal RMS arising in the retroperitoneum. These data suggest that debulking tumors of embryonal histology improves outcome further. This approach will be assessed in IRSG V.

Adolescent↗
PubMed1999

Clinical significance of follicular lymphoma with monocytoid B cells. Non-Hodgkin's Lymphoma Classification Project.

Although follicular lymphoma (FL) is very common in the Western world, very little information is available regarding the frequency and significance of monocytoid B cells (MBC) in FL. We recently completed a clinicopathologic study of 1,378 cases of non-Hodgkin's lymphoma. In this study, a research data sheet was designed to conduct research on several types of lymphomas, one part of which was evaluating the presence of intrafollicular clear cells and extrafollicular MBC in 326 cases diagnosed as FL by one of the pathologists (B.N.N.). For each case diagnosed as FL, the presence of intrafollicular clear cells or extrafollicular MBC was scored as pure FL (no intrafollicular clear cells or extrafollicular MBC), FL with intrafollicular clear cells, FL with less than 5% MBC, and FL with greater than 5% MBC. Of 326 cases classified as FL, 252 (77%) had no intrafollicular clear cells or extrafollicular MBC and therefore were called pure FL. In 36 cases (11%), intrafollicular clear cells were seen, but no extrafollicular MBC. There were no clinical differences between such cases and the 252 cases of pure FL. In eight cases of FL (2%), MBC clusters were rare (<5%). In contrast, 30 cases of FL (9%) had a prominent (>5%) proliferation of extrafollicular MBC; these 30 cases had a significantly shorter failure-free survival (P = .001) and overall survival (P = .04) than the 252 cases of pure FL. The shorter survival of these 30 cases appeared to be independent of the international prognostic index (IPI), stage, and treatment. The FFS of this group remained shorter than that of cases with pure FL when the analysis was restricted to patients treated with Adriamycin-containing regimens and either a favorable (0 to 3) IPI score (P = .001) or advanced stage (III/IV) disease (P = .015). In conclusion, FL with a prominent (>5%) MBC component constitutes a substantial proportion (9%) of FL and has distinctive morphology, and these patients have a significantly shorter survival than those with pure FL.

B-Lymphocytes↗
PubMed1999

Process, not representation: reply to Radvansky (1999).

The size of fan effects is determined by processes at retrieval, not by whether or not information is represented as situations. Evidence contradicts G. A. Radvansky's (1999) claim that time to retrieve information from a situation does not depend on the number of elements in the situation. Moreover, Radvansky's principles for ascribing situational models to experiments appear to be post hoc ways of redescribing the data. On the other hand, the evidence does support the Adaptive Control of Thought--Rational (ACT-R) assumption that participants can adjust their attentional weightings and so produce differential fan effects. Moreover, the ACT-R theory of the fan effect is consistent with many other findings.

Association Learning↗
PubMed1999

Practice and retention: a unifying analysis.

What is the strength of a memory trace that has received various practices at times tj in the past? The strength accumulation equation proposes the following: strength = sigma tj-d, where the summation is over the practices of the trace. This equation predicts both the power law of practice and the power law of retention. This article reports the fits of the predictions of this equation to 5 experiments. Across these experiments, participants received as many as 240 trials of practice distributed over intervals as long as 400 days. The experiments also varied whether participants were just practicing retrieving an item or practicing applying a relatively complex rule. A model based on this equation successfully fit all the data when it was assumed that the passage of psychological time slowed after the experimental session. The strength accumulation equation was compared with other conceptions of the retention function and the relationship of the retention function to the practice function.

Humans↗
PubMed1999

Mutations in the skeletal muscle alpha-actin gene in patients with actin myopathy and nemaline myopathy.

Muscle contraction results from the force generated between the thin filament protein actin and the thick filament protein myosin, which causes the thick and thin muscle filaments to slide past each other. There are skeletal muscle, cardiac muscle, smooth muscle and non-muscle isoforms of both actin and myosin. Inherited diseases in humans have been associated with defects in cardiac actin (dilated cardiomyopathy and hypertrophic cardiomyopathy), cardiac myosin (hypertrophic cardiomyopathy) and non-muscle myosin (deafness). Here we report that mutations in the human skeletal muscle alpha-actin gene (ACTA1) are associated with two different muscle diseases, 'congenital myopathy with excess of thin myofilaments' (actin myopathy) and nemaline myopathy. Both diseases are characterized by structural abnormalities of the muscle fibres and variable degrees of muscle weakness. We have identified 15 different missense mutations resulting in 14 different amino acid changes. The missense mutations in ACTA1 are distributed throughout all six coding exons, and some involve known functional domains of actin. Approximately half of the patients died within their first year, but two female patients have survived into their thirties and have children. We identified dominant mutations in all but 1 of 14 families, with the missense mutations being single and heterozygous. The only family showing dominant inheritance comprised a 33-year-old affected mother and her two affected and two unaffected children. In another family, the clinically unaffected father is a somatic mosaic for the mutation seen in both of his affected children. We identified recessive mutations in one family in which the two affected siblings had heterozygous mutations in two different exons, one paternally and the other maternally inherited. We also identified de novo mutations in seven sporadic probands for which it was possible to analyse parental DNA.

Actins↗
PubMed1999

Expression of Bcl-2 and Bax in oligodendrogliomas and their relationship to apoptosis.

Apoptotic bodies are frequently found in oligodendrogliomas, particularly in the anaplastic subtype. A range of proteins, such as those of the Bcl family, are implicated in the control of apoptosis. The ratio of antagonists of apoptosis, such as Bcl-2, to agonists, such as Bax, is thought to determine the outcome for a particular cell. This study aimed to determine the expression of Bcl-2 and Bax proteins in a series of oligodendrogliomas and to relate the expression of these to measures of apoptosis. Immunohistochemistry was used to detect the expression of Bcl-2 and Bax in an archival series of 32 oligodendrogliomas. The results were scored semiquantitatively for the extent and intensity of tumour staining. Apoptosis indices were determined by counting apoptotic bodies on haematoxylin and eosin staining and the percentage of cells showing a positive reaction with the TdT-mediated dUTP-biotin nick end-labelling technique (TUNEL). Granular cytoplasmic staining for Bcl-2 was seen in tumour cells in 81% of cases. Cases with a strong intensity (but not extent) of staining showed a lower TUNEL index (P=0.038). Bcl-2 expression was identified in the walls of intratumoural blood vessels in 55% of cases and in peri-tumoural neurones (where present) in 87%. Bax expression was detected in tumour cells in 69% of cases but no relationship to TI was detected. Bax positivity was seen in blood vessels in 44% of cases and peri-tumoural neurones in 60%. Bcl-2 and Bax were concluded to be expressed in a high proportion of oligodendrogliomas, suggesting that they may exert a regulatory role in cell death in these tumours.

Apoptosis↗
PubMed1999

Laser and curing light induced in vitro pulpal temperature changes.

OBJECTIVE: This study was conducted to compare in vitro pulp chamber temperature changes induced by conventional curing light and argon laser under common conditions. SUMMARY BACKGROUND DATA: Previous in vitro studies have shown that impacting the surface of teeth with either an argon laser or conventional curing light causes pulp temperature increases of various degrees. METHODS: The sample tooth had a class V composite restoration placed with 2.48-mm distance from the surface of the composite to a Thermister Thermometer. The thermometer was inserted into the cutaway pulp chamber to measure the temperature increase from stabilized room temperature, which was caused by exposure to argon laser or conventional curing light. RESULTS: Temperature increases for the argon laser for the recommended curing time were 3 degrees F or less. The longer the exposure times for either method of curing, the higher the temperature increased. CONCLUSION: At recommended curing times, in vitro pulp chamber temperature increases from laser units were significantly lower than those of the conventional curing lights.

Analysis of Variance↗