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Biomedical subjects

J Gerson

Publications and source records attributed to J Gerson.

12 recordsLinked to original sources
PubMed1996

Alzheimer disease and subcortical ischemic vascular dementia: evaluation by combining MR imaging segmentation and H-1 MR spectroscopic imaging.

PURPOSE: To determine the association between H-1 magnetic resonance (MR) spectroscopic imaging and MR imaging differences in subjects with Alzheimer disease (AD) or subcortical ischemic vascular dementia (SIVD) versus control subjects and if both studies combined enable discrimination of AD from control subjects better than either study alone. MATERIALS AND METHODS: Measures were obtained in nine AD, eight SIVD, and 11 control subjects with MR imaging segmentation software. RESULTS: Statistically significantly lower N-acetylaspartate/choline-containing metabolites (Cho) and higher Cho/creatine-containing metabolites in posterior mesial gray matter in AD versus control subjects were independent of MR imagining differences. Combined measures allowed correct classification of AD and control subjects, but none of the MR measures allowed accurate discrimination between AD and SIVD subjects. CONCLUSION: Between-group differences in tissue-type contributions to H-1 MR spectroscopic imaging voxels must be accounted for when reporting H-1 MR spectroscopic imaging data in AD, SIVD, and control subjects. Combined studies allowed more accurate discrimination between AD and control subjects than either study alone.

Aged↗
PubMed1995

H-1 MR spectroscopic imaging of white matter signal hyperintensities: Alzheimer disease and ischemic vascular dementia.

PURPOSE: To investigate the association of white matter signal hyperintensities (WMSHs) with changes in hydrogen-1 metabolites. MATERIALS AND METHODS: T2-weighted magnetic resonance (MR) imaging and H-1 MR spectroscopic imaging were performed in 21 elderly control subjects without or with minimal WMSHs, eight elderly subjects with substantial WMSHs, 11 probable Alzheimer disease patients with WMSHs, and eight ischemic vascular dementia (IVD) patients with WMSHs. N-acetylaspartate (NAA), choline-containing metabolites (Cho), and creatine-containing metabolites (Cr) were analyzed. RESULTS: Differences in regional metabolite levels were found within the supraventricular brain of elderly control subjects. In Alzheimer disease patients, extensive WMSHs showed a lower percentage of NAA and a higher percentage of Cho compared with contralateral normal-appearing white matter (NAWM); in IVD patients, extensive and large WMSHs were associated with a higher percentage of Cho and a lower percentage of Cr compared with contralateral NAWM. CONCLUSION: Regional metabolite variation and the presence of WMSHs are important covariants that must be accounted for in analysis of MR spectroscopic data.

Aged↗
PubMed1994

Equivalent dipole parameter estimation using simulated annealing.

Equivalent-electrical dipole source modeling of evoked potential signals requires complicated non-linear multivariate optimization. Newton and non-linear simplex optimization methods often converge to a local minimum, and their results are affected by the procedure's starting parameter estimates. This paper describes simulated annealing, a more robust and resistant global optimization method. As an illustrative example, both the simplex and simulated annealing algorithms were used for parameter estimation in modeling wave V of the brain-stem auditory evoked potential (BAEP) using a single decaying sinusoid dipole source. Data for a single subject from 3000 responses to stimuli on each of 2 days were recorded, with modeling performed on 1000 response subaverages. Each estimation problem was run with 5 different sets of starting parameters. Simulated annealing always converged to the global minimum regardless of the starting parameter estimates while simplex often converged to markedly different solutions for different starting parameter estimates. No association was apparent between the simplex's converging to a local minimum and the closeness of the starting estimates to the true parameter values. Implementation of simulated annealing is discussed in terms of cooling schedules and other procedure parameters.

Acoustic Stimulation↗
PubMed1994

Investigation of applied forces in alphanumeric keyboard work.

This paper considers one way that occupational health professionals can assess the force exerted by keyboard users and the possible relationship between that force and the key force-displacement relationship. First, three personal-computer keyboards with the standard QWERTY layouts were tested as described by the American National Standard for Human Factors Engineering of Visual Display workstations (ANSI/HFS 100-1988) to determine the peak forces, 0.47-0.89N; displacements prior to the "breakaway" force that acknowledges key registration, 2.0-2.5 mm; and total key travel, 3.3-4.3 mm. Second, keyboard reaction forces were recorded while 10 subjects typed 4 alphanumeric sentences on the keyboards. It was found that the peak forces corresponding to each keystroke were 2.5 to 3.9 times the required activation forces, indicating that the subjects consistently displaced the keys to their limits. The average of the peak forces for all keystrokes was lowest for the keyboard with the lowest required activation force. It was concluded that keyboard reaction forces can be used as an index of finger forces for keying tasks. Further studies are necessary to evaluate the relationship between keyboard reaction forces, fatigue, and chronic muscle, tendon, and nerve disorders.

Biomechanical Phenomena↗
PubMed1993

The reliability of P50 suppression as measured by the conditioning/testing ratio is vastly improved by dipole modeling.

Suppression of auditory P50 evoked potential amplitude to the second of a pair of clicks is potentially important in psychiatric research because it has been shown to be abnormal in both schizophrenics and their relatives. However, its clinical utility using the standard single-channel electroencephalographic (EEG) peak picking methodology is under question because of low test-retest reliability. Dipole Components Modeling of the P50 component was attempted as a method for increasing the reliability of the P50 suppression measure. It was hypothesized that this procedure might work because of pooling of noise from the two responses and because of the use of topographic information. Six replications of a P50 suppression paradigm in 12 subjects were analyzed. Reliability using peak picking was 0.27, and was significantly increased to 0.63 using dipole modeling. Dipole modeling was helpful not only for better modeling the P50 when it was present, but also for deciding that there was no P50 response in one subject.

Acoustic Stimulation↗
PubMed1991

A study of the effect of perchloroethylene exposure on the reproductive outcomes of wives of dry-cleaning workers.

The purpose of this investigation was to compare the reproductive outcomes of wives of men exposed to perchloroethylene in the dry-cleaning industry compared to those of wives of laundry workers. Seventeen female partners of dry cleaners and 32 partners of laundry workers were interviewed. The number of pregnancies and the standardized fertility ratios were similar between the two groups. Wives of dry cleaners did not have higher rates of spontaneous abortions. However, wives of dry cleaners were more than twice as likely to have a history of attempting to become pregnant for more than 12 months or to have sought care for an infertility problem. Cox proportional hazards models indicated that dry-cleaners' wives had half of the per-cycle pregnancy rate of wives of laundry workers, when controlling for other potential confounders (estimated rate ratio of 0.54, 95% C.I. = 0.23, 1.27).

Adult↗
PubMed1981

Systemic and in situ natural killer and suppressor cell activities in mice bearing progressively growing murine sarcoma-virus-induced tumors.

The activity of systemic and in situ natural killer (NK) cells was measured in 3- to 5-week-old CBA mice with progressively growing murine sarcoma virus (MSV)-induced tumors. Splenic NK activity was depressed in tumor-bearing mice. NK activity was quite low or not detectable in unfractionated cell suspensions from the tumors 10-12 days after inoculation of virus, but activity was observed upon depletion of phagocytic and/or adherent cells. To determine whether this in situ inhibition of NK activity was correlated with the presence of previously described suppressor cells, subpopulations of cells from the tumors were tested for their ability to suppress various responses of normal spleen cells: NK activity, lymphoproliferative responses to concanavalin A, and proliferation-independent production of macrophage inhibition factor. A similar pattern of suppressor activity was seen in all of the assays, indicating the presence of pleiotropic suppressor cells in progressively growing MSV-induced tumors.

Animals↗
PubMed1977

The prognostic value of acute phase reactants in patients with neuroblastoma.

As part of a more extensive study of the immune response in children with neuroblastoma, serum immunoglobulin and alpha-glycoprotein levels were measured in 58 patients. Twenty-nine children were studied at diagnosis, 18 at some time during the first 2 years of treatment, and 11 who were apparently cured after treatment had been completed. No correlation was found between the levels of IgG, IgA, and IgM and the clinical status of the patient. The acute phase reactants (alpha-1-antitrypsin, haptoglobin, C3 component of complement and orosomucoid) varied with the disease status. Twenty-seven of the 29 patients had elevated levels at the time of diagnosis. Alpha-1-antitrypsin and haptoglobin were the two proteins that most accurately reflection the clinical status; C3 component of complement was not infrequently normal when the disease was active; and orosomucoid was sometimes raised in patients apparently in remission. Serial measurement of alpha-1-antitrypsin and haptoglobin could provide a useful means of detecting early relapse in patients responding to treatment.

Adolescent↗
PubMed1976

Spontaneous regression of neuroblastoma.

Case of spontaneous regression of neuroblastoma continue to occur in the present multimodal therapy era at institutions where physicians are prepared to withhold treatment on certain patients with residual primary or metastatic disease. From a survey of the 22 member institutions of Children's Cancer Study Group, seven hospitals submitted data on 24 neuroblastoma patients whose disease underwent regression after minimal, unusual, or no treatment. An analysis of these patients and of 33 patients form two large series in the literature shows that the majority of patients are infants with Stage II or Stage IVS disease. The spontaneous regression usually consists of complete disappearance of the disease, but in some neuroblastomas, maturation to ganglioneuroma takes place. The various factors that may influence regression are discussed.

Age Factors↗