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Biomedical subjects

F Symons

Publications and source records attributed to F Symons.

9 recordsLinked to original sources
PubMed2001

Self-injurious behavior: gene-brain-behavior relationships.

This paper summarizes a conference held at the National Institute of Child Health and Human Development on December 6-7, 1999, on self-injurious behavior [SIB] in developmental disabilities. Twenty-six of the top researchers in the U.S. from this field representing 13 different disciplines discussed environmental mechanisms, epidemiology, behavioral and pharmacological intervention strategies, neurochemical substrates, genetic syndromes in which SIB is a prominent behavioral phenotype, neurobiological and neurodevelopmental factors affecting SIB in humans as well as a variety of animal models of SIB. Findings over the last decade, especially new discoveries since 1995, were emphasized. SIB is a rapidly growing area of scientific interest to both basic and applied researchers. In many respects it is a model for the study of gene-brain-behavior relationships in developmental disabilities.

Animals↗
PubMed1997

Multivariate reconstruction of lymphocyte profiles in a two-dimensional graphical model as a tool for the investigation of lymphocyte subset distribution in health and disease.

Advanced multivariate data-analytical techniques are proposed to concisely represent and evaluate complex lymphocyte profiles (i.e., compound lymphocyte subset distributions) of individual subjects in easily interpretable, two-dimensional, graphical correlation biplots. The lymphocyte profile of each subject is represented by its location in the model, and the score of a subject for a particular lymphocyte subset is inferred from the perpendicular projection on a rotated axis that coincides with this lymphocyte subset. Simultaneously, the model yields information about the correlation between the lymphocyte subsets. Furthermore, individuals with aberrant lymphocyte profiles can be easily identified. In case studies of 80 healthy donors and of 40 patients with multiple myeloma, 10 patients with monoclonal gammopathy of undetermined significance, and 50 age- and sex-matched healthy donors, reconstruction of the two-dimensional lymphocyte profiles from 27 flow-cytometric characterized lymphocyte subsets succeeded in representing 43% and 51% of the total information (variability) contained within the 80 x 27 (= 2,160) and 100 x 27 (= 2,700) flow cytometry measurements, respectively. It is concluded from the present studies that the correlation biplot represents a unique and powerful tool to concisely describe, represent, and analyze complex lymphocyte profiles of individual subjects and the heterogeneity in lymphocyte profiles among these subjects.

Adult↗
PubMed1995

The Leishmania promastigote surface antigen 2 complex is differentially expressed during the parasite life cycle.

The promastigote surface antigen 2 (PSA-2) complex comprises a family of antigenically similar polypeptides of M(r) 96,000, 80,000 and 50,000, anchored to the membrane with glycosylphosphatidylinositol. Although PSA-2 was initially detected only in promastigotes, Northern blot analysis indicated that mRNA transcripts are also present in amastigotes. Unlike the situation in promastigotes, where at least four major transcripts (2.6-5.3 kb) were detected, only one major (2.6 kb) and two minor transcripts were present in amastigotes. A cDNA clone encoding a member of the PSA-2 family expressed in amastigotes was isolated using DNA probes. The predicted protein sequence of M(r) 40,000 is distinct from promastigote sequences, but shows significant similarity to previously described members of the family from L major and L amazonensis. Antibodies to the carboxyl terminal sequence conserved in all L major PSA-2 studied to date, as well as antibodies affinity purified on the amastigote cDNA-derived polypeptide recognized a major M(r) 50,000 amastigote polypeptide. Immuno-electron microscopy localized both promastigote and amastigote PSA-2 to the cell surface. The expression of PSA-2 polypeptides during the transformation of amastigotes into promastigotes was ordered in a time-dependent manner, with the promastigote M(r) 80000 polypeptide appearing first, followed by the M(r) 96000 polypeptide. In contrast to the glycosylphosphatidylinositol anchor of promastigote PSA-2, which could be hydrolysed by phosphatidylinositol-specific phospholipase C, the amastigote form was resistant to this enzyme.

Amidohydrolases↗
PubMed1994

Instructional conditions and stereotyped behavior: the function of prompts.

The relationship of instructional prompts to rate of task completion and stereotypy was studied in one adolescent student with autism and high-frequency stereotypic behavior. Using an ABAB design, one experiment was conducted which systematically examined the role of prompts on (a) task completion and (b) time engaged in stereotyped behavior. Results suggested that prompts had little effect on the rate of task completion across sessions but did reduce time spent in stereotypies. These results are discussed in relation to stereotypies and implications for intervention and instruction.

Adolescent↗
PubMed1987

Systematic analysis of the long-chain components of Eubacterium lentum.

The cellular long-chain component patterns of 33 strains of Eubacterium lentum were determined by gas chromatography. Two main types of long-chain component patterns were distinguished. The first (26 strains) was characterized by saturated branched-chain fatty acids (br14:0, br15:0, br16:0 and br17:0). The second (7 strains) did not contain branched-chain fatty acids and was characterized by saturated straight-chain fatty acids (11:0, 12:0, 14:0 and 16:0). Both types contained fatty aldehydes and their respective dimethyl acetals (14ald and 14dma, 16ald and 16dma). br16dma was only found in the first type. The G + C content of the DNA (Tm) of the 33 strains varied between 63.7 and 69.1 mol %. Canonical correlation analysis distinguished three subtypes within the first main type.

Base Composition↗
PubMedDate not supplied

Occupational hearing loss. The significance of asymmetrical hearing thresholds.

In 1873 consecutive patients referred for compensation assessment for presumed industrial hearing loss, 281 (15%) had an average difference in hearing threshold between the ears of 15 dB at 1/2, 1, 2 and 4 kHz. An unrelated cause was found in 115 (6%). It was due to trauma in 37 (2%), unexplained in 32 (1.7%) and attributed to noise exposure in 97 (5.2%). The possible mechanisms for noise as a cause are discussed and include shielding of one ear from noise, unequal recovery after severe noise exposure, and unequal sensitivity of the ears. After extensive investigation, including X-rays, vestibular tests and some myelograms, no treatable disorder was discovered.

Audiometry↗
PubMedDate not supplied

Puretone threshold estimation from acoustic reflex thresholds--a myth?

There have been repeated claims in the literature that hearing thresholds can be estimated by means of acoustic reflex threshold (ART) measurements. We have evaluated this thesis in depth by examining the statistical relationships between conventional puretone thresholds and ARTs for tonal and broadband stimuli in a large sample (1207) of adult patients with sensorineural hearing loss; they were compensation claimants for noise-induced loss. All relevant data were stored in a computer database, and analysed using the Statistical Package for the Social Sciences (SPSS). The relationships were examined from two distinct standpoints; dependency of ART's upon puretone thresholds, and prediction of audiogram features using ARTs. The average tonal ART is constant up to 70 dB average loss, and thereafter increases rapidly. The broadband noise ART increases steadily for average losses of 10 to 85 dB. The convergence principle is therefore valid up to 70 dB in this population. The predictor suggested by Niemeyer & Sesterhenn does not fit the data. The single ART which best predicts average loss is that for white noise, but a multiple regression prediction using the white noise and 500 Hz ARTs is preferable. Predictive accuracy is dependent upon audiogram slope, but the latter cannot be predicted usefully from the ART measures used. None of the predictors studied is adequate for medico-legal assessment and the method is probably not sufficiently accurate for clinical use in adults.

Adult↗