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Biomedical subjects

R H Felton

Publications and source records attributed to R H Felton.

At least 19 recordsLinked to original sources
PubMed1994

Students with word finding disorders: three case studies.

Case studies of three students of different ages with different types and degrees of word finding disorders are presented. One student is at the beginning of his school career, one has been in school for 7 years, and the third individual is a young adult who left school after completing only 11 grades. Each student's word finding profile and characteristics are presented as well as the impact of the disorder upon school performance particularly in the area of reading. Recommendations are made for intervention involving collaboration between speech-language pathologists and educators.

Achievement↗
PubMed1993

Effects of instruction on the decoding skills of children with phonological-processing problems.

This article reviews research carried out by the Bowman Gray Learning Disabilities Project concerning the role of instruction in the acquisition of word-identification (decoding) skills in children at risk for reading disabilities. A group of 81 kindergarten children were identified as at risk for reading disabilities based on teacher assessment and weak or deficient phonological-processing skills. These children were classified as to type of phonological-processing problem (i.e., phonological awareness or retrieval of phonological information) and were randomly assigned to either a Code or Context instructional method for first and second grades. Children who received Code instruction scored higher than children receiving context instruction on a variety of reading and spelling measures at the end of first and second grades. The elements of the Code instructional program considered critical to the success of a beginning reading instruction program for children with phonological processing problems are discussed.

Acoustic Stimulation↗
PubMed1992

A reading level match study of nonword reading skills in poor readers with varying IQ.

This study evaluated the hypothesis that poor readers are characterized by poor nonword reading skills, but that a specific deficit, as opposed to a developmental lag, in nonword reading will be found only in subjects whose reading is discrepant from intellectual ability. To test this hypothesis, we measured nonword reading skills in 93 (64 male, 29 female) third-grade poor readers and 54 (37 male, 17 female) fifth-grade poor readers (with and without reading/IQ discrepancies) who were matched to 147 (81 male, 66 female) nondisabled first graders on word identification skills. Results showed third- and fifth-grade poor readers to be significantly more impaired than word-identification level match first graders on all measures on nonword reading. These findings were not related to the verbal IQ level within the poor reader groups and, thus, provide strong evidence for a deficit in nonword reading skills that is not explained by verbal intelligence.

Age Factors↗
PubMed1992

Six-year follow-up of a case of radiation injury following treatment for medulloblastoma.

Recent reports in the literature have documented long-term sequelae of radiation treatment in children, the most notable of which are diminished endocrine functioning and decline in intellectual ability. A case is presented in which both these long-term effects were seen 7 years after radiation treatment for medulloblastoma. Growth hormone and thyroid hormone deficiencies were identified and treated. Full-Scale IQ dropped from the 79th percentile to the 3rd percentile, and neuropsychological functioning ranged from normal to impaired. However, magnetic resonance imaging reveals few direct imaging correlates of J.M.'s neuropsychological deficits. If identified, hormone deficiencies in such patients can be successfully treated; intellectual deficits may present more of a management problem. In this case, cognitive deficits have contributed to considerable difficulty in school; however, with special classes and modifications, the patient is making progress. Our findings indicate that the long-term outcome for children with radiation injury may be improved significantly with hormone therapy and appropriate academic intervention, and argue strongly for systematic, sequential follow-up of such children so that appropriate intervention can be implemented and continued as necessary.

Body Height↗
PubMed1990

Neuropsychological profile of adult dyslexics.

One hundred and fifteen adults with well-documented childhood reading status underwent a series of neuropsychological tests including tests of memory, attention, phonological processing, and visual perceptual skills in an attempt to define the neuropsychological profile of dyslexia in adulthood. Compared to a normal nonreading disabled sample, subjects with a history of reading disability performed consistently poorer on most neuropsychological tests. However, after covarying for intelligence and socioeconomic status, only tests of rapid naming, phonological awareness, and nonword reading were significant discriminating measures. The hypothesis that deficits in phonological processing comprise the core cognitive deficits in adults with a history of reading disability was supported. Independent of current adult reading ability, measures of nonword reading, phonological awareness, and rapid naming serve as indicators of a childhood history of reading disability.

Adult↗
PubMed1989

Long-term follow-up of a childhood amnesic syndrome.

In attempting to explain observed dissociations between impaired and preserved memory functioning in amnesia, various dichotomous memory systems (e.g., procedural versus declarative, episodic versus semantic, working versus reference memory) have often been employed. In such cases, the assumption has been that memory subserved by one system is preserved, while that of the other system is impaired. Cohen and Squire have suggested that in amnesia, declarative memory is impaired, although procedural memory is preserved. Long-term follow-up of a densely amnesic patient refutes this view by demonstrating significant anterograde learning of school subjects including reading, vocabulary, spelling, and arithmetic, all of which include some component of declarative memory. It appears that the procedural/declarative dichotomy is not adequate to explain preserved memory in amnesia.

Adolescent↗
PubMed1989

Cognitive deficits in reading disability and attention deficit disorder.

This paper presents data from three studies (a cross-sectional study of school-referred children, a test-retest study of subtypes of reading disabilities, and a study of a large, random sample of first graders) that focus on specifying the cognitive deficits associated with reading difficulties and separating them from those associated with attentional deficits. The cognitive deficits associated with difficulty in reading were consistent across samples, developmental levels, definitions, and subtypes of reading disabilities. With IQ, age, and sex controlled for, poor readers were significantly impaired on measures of naming and phonological awareness. The effects of attentional deficits were more variable and complex but were clearly separate from the reading disability effects.

Attention↗
PubMed1987

Separate verbal memory and naming deficits in attention deficit disorder and reading disability.

In this study, verbal memory and naming abilities were investigated in reading disabled (RD) and control children who were characterized according to the presence or absence of attention deficit disorder (ADD). Results indicate that deficits in learning and memory for recently acquired information occur as a function of ADD rather than RD while deficits in naming are specific to RD rather than ADD. We conclude that ADD is a major source of additional and separate cognitive morbidity in RD children.

Attention Deficit Disorder with Hyperactivity↗
PubMed1984

Solvent proton magnetic resonance dispersion in protocatechuate 3,4-dioxygenase and complexes with 3-halo-4-hydroxybenzoate inhibitors.

Solvent proton nuclear magnetic dispersion studies at 25, 100, and 300 MHz have been performed on protocatechuate 3,4-dioxygenase (PCD) and its complexes with 3-chloro-4-hydroxybenzoate and 3-fluoro-4-hydroxybenzoate. Longitudinal and transverse relaxation rates were measured for these compounds and for the apoenzyme. The paramagnetic enhancement of solvent T1 is interpreted in terms of dominant dipole-dipole relaxation of fast-exchanging solvent protons with a negligible contribution from outer sphere relaxation and an electronic spin relaxation time of 0.5 ns for the high-spin ferric ion. A discrepancy between the observed T2 at 300 MHz and that calculated by assuming the usual dipolar relaxation provides evidence for an additional Curie-spin dipolar or hyperfine interaction between the proton and iron. Quantitation of the additional relaxivity provides an estimated chemical exchange lifetime of 0.1-0.14 microseconds, which suggests proton exchange by a hydroxide ligand. Proton-to-iron distances are 2.7-3.1 A in PCD and lengthen to 3.6-4.1 A in the halohydroxybenzoate complexes.

Apoenzymes↗
PubMed1979

Conformational transitions and vibronic couplings in acid ferricytochrome c: a resonance Raman study.

Resonance Raman spectral changes in ferricytochrome c as a function of pH between 6.7 and 1.0 are reported and the structural implication is discussed in terms of the "core-expansion" model advanced by L. D. Spaulding et al. [(1975) J. Am. Chem. Soc. 97, 2517]. The data are interpreted as indicating the iron in high-spin ferricytochrome c (at pH 2.0) with two water molecules as axial ligands lies in the plane of the porphyrin ring. At pH 1.0 there is a different high-spin form of cytochrome c which has an estimated iron out-of-plane distance of approximately 0.46 A. The effect of a monovalent anion at pH 2.0 is to produce a thermal spin mixture with predominant low-spin species. Excitation at approximately 620 nm in acid cytochrome c (pH 2.0) enhances only three depolarized ring vibrations at 1623, 1555, and 764 cm-1. Marked enhancement of depolarized modes relative to polarized and anomalously polarized modes is attributed to the vibronic coupling between porphyrin pi leads to pi and porphyrin pi leads to iron (dpi) charge-transfer states.

Animals↗
PubMed1976

Laser Raman spectra of oxidized hydroperoxidases.

Resonance Raman spectra of oxidized hydroperoxidases are examined for shifts in the structure-sensitive, anomalously polarized bands; these are found, respectively, at 1576, 1567 and 1570 cm-1 in the high-spin resting enzymes: horse radish peroxidase, horse blood catalase, and cytochrome c peroxidase. In compound II of horse radish peroxidase and horse blood catalase, and in the enzyme-substrate complex of cytochrome c peroxidase, this band appears at 1587-1590 cm-1 and indicates the iron atom is now in-plane with the porphyrin ring. Weak Raman scattering found with horse radish peroxidase I is consistant with a porphyrin eta-cation radical formulation.

Animals↗
PubMed1974

The cation radicals of free base and zinc bacteriochlorin, bacteriochlorophyll, and bacteriopheophytin.

One-electron oxidation of zinc tetraphenylbacteriochlorin and its metal-free base yielded stable cation radicals. Electron spin resonance hyperfine splittings were assigned by selective deuterations. These results indicate that the protons of the saturated rings of the bacteriochlorins carry large spin densities, in accord with molecular orbital calculations. Comparison in vitro of the optical spectra of bacteriochlorins and their cation radicals with those of bacteriochlorophyll show close correspondence and suggest that the electron spin resonance data from the former may also prove a guide to the biological molecule. The surprising similarity in properties between the radicals of free base and zinc bacteriochlorins is maintained in the chlorophylls: cation radicals of bacteriopheophytin and methyl pheophorbide (the free bases of bacteriochlorophyll and methyl chlorophyllide, respectively) exhibit electron spin resonance properties similar to those of their magnesium-containing derivatives. The possibility that metal-free chlorophylls participate in photosynthesis is discussed.

Journal Article↗