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P W Fox

Publications and source records attributed to P W Fox.

7 recordsLinked to original sources
PubMed1997

Proteoglycans in the human sclera. Evidence for the presence of aggrecan.

PURPOSE: The proteoglycans synthesized and accumulated within the adult human sclera (aged 50 to 80 years) were identified by their size, glycosaminoglycan side chains, and core proteins in an effort to characterize the proteoglycan content of the human sclera. METHODS: Sclerae, unlabeled, or radiolabeled in organ culture with 35SO4 or 3H-proline, were extracted in 4M guanidine-HCl and separated by Sepharose CL-2B and Superose 6 forced-pressure liquid chromatography. Peak fractions, identified by glycosaminoglycan content or radioactivity, were pooled and subjected to G-50 chromatography or sodium dodecyl sulfate-polyacrylamide gel electrophoresis before and after digestion with specific glycosidases. Scleral proteoglycan core proteins were identified in Western blot analysis using specific antisera to decorin, biglycan, and aggrecan. Reverse transcription-polymerase chain reaction analyses were carried out on human scleral fibroblast RNA to confirm the transcription of one scleral proteoglycan. Proteoglycans were localized on sections of scleral tissue using specific antisera. RESULTS: After chromatography on CL-2B, scleral proteoglycans could be resolved into three major peaks, PG-1, PG-2, and PG-3. The largest scleral proteoglycan, PG-1, contained chondroitin sulfate and keratan sulfate glycosaminoglycan side chains. Results of Western blot analyses indicated that the core protein of PG-1 is the aggrecan core protein, migrating at approximately 350 kDa. Reverse transcription-polymerase chain reaction analyses confirmed that human scleral fibroblasts transcribe aggrecan in vitro and in vivo. PG-2 and PG-3 were identified as biglycan and decorin in Western blot analyses using antibiglycan and antidecorin antibodies, respectively. Immunostaining results indicated that aggrecan, biglycan, and decorin are distributed throughout the thickness of the human sclera. CONCLUSIONS: The adult human sclera contains three major proteoglycans; aggrecan, biglycan, and decorin. It is likely that these proteoglycans contribute to the structural properties of the sclera and that the ratios of these proteoglycans will change with age, specific region, and condition of the sclera.

Aged↗
PubMed1996

Genetic and environmental contributions to the acquisition of a motor skill.

Practice, with feedback, is a fundamental variable that influences the aquisition of motor skills: with it, everyone improves, but some improve more than others. This simple fact has led to frequent debate over the relative importance of genetic and environmental influences on motor learning. In principle these factors could influence subjects' initial level of proficiency, their rate of improvement or their final level of attainment. The problem has been investigated using the rotary pursuit (RP) task, in which subjects learn to track a rotating target with a stylus; this is a factorially pure task which is relatively unaffected by cognitive or verbal factors. Earlier studies of twins reared together indicated that heredity was the primary factor responsible for individual differences in motor skill. Here we have studied learning in a sample of monozygotic (MZA) and dizygotic (DZA) twins who had been reared apart. Heritability of performance was high even in the initial phase, and increased with practice. The rate of learning was also significantly heritable. We propose that the effect of practice is to decrease the effect of environmental variation (previous learning) and increase the relative strength of genetic influences on motor performance.

Adult↗
PubMed1993

When less is more: representation and selective memory in expert problem solving.

Few studies of problem-solving expertise in professional domains have undertaken independent assessments of how domain-specific knowledge contributes to the development of problem representations as well as subsequent memory for task information. These issues were investigated in the present study by asking participants at three levels of training and experience (novice, trainee, and expert) in a medical specialty to solve two complex diagnostic problems (patient cases) selected from medical records of a university hospital. The subjects were also asked to provide an incidental free recall of the patient information contained in each case immediately after problem solving and one week later. Problem representations (identified as "lines of reasoning") used by each subject in each case were determined from an analysis of thinking-aloud protocols generated during problem solving. The three groups did not differ on the overall amount of case information recalled at the immediate retention test and did not show selective recall for information statements that were directly relevant to the lines of reasoning used during problem solving. After one week, however, the expert physicians remembered fewer information units than novices but showed selective retention for case information contained in the lines of reasoning used to reach a diagnosis. Experts also increased their recall of specific diagnostic interpretations contained in their initial problem-solving experience while novices did not demonstrate evidence of their problem representations in recalling case information.

Cardiology↗
PubMed1992

Unexceptional spatial memory in an exceptional memorist.

Rajan Mahadevan evidences an exceptional memory for arrays of digits. We tested whether Rajan's spatial memory was likewise exceptional. Eight control Ss and Rajan were instructed to remember the position and orientation of 48 images of common objects shown either to the left or the right of fixation and facing either left or right. Rajan's accuracy for judging whether the position and orientation of these pictures had changed when they were shown in a different sequence was lower than that of control Ss for both judgments. Rajan's exceptional memory capacity apparently does not extend to spatial relations.

Adult↗
PubMed1989

Inhibiting the Lombard effect.

The Lombard effect is the tendency to increase one's vocal intensity in noise. The present study reports three experiments that test the robustness of the Lombard effect when speakers are given instructions and training with visual feedback to help suppress it. The Lombard effect was found to be extremely stable and robust. Instructions alone had little influence on the response to the noise among untrained speakers. When visual feedback correlated with vocal intensity was presented, however, subjects could inhibit the Lombard response. Furthermore, the inhibition remained after the visual feedback was removed. The data are interpreted as indicating that the Lombard response is largely automatic and not ordinarily under volitional control. When subjects do learn to suppress the effect, they seem to do so by changing overall vocal level rather than their specific response to the noise.

Feedback↗
PubMedDate not supplied

Age differences in hypermnesia: word gain versus word loss.

A hypermnesic task was administered to 82 younger adults (ages 27-39), 63 middle-aged adults (ages 40-59), and 119 older adults (ages 60-87). Previous research suggests that relational encoding prevents loss of items and item-specific encoding promotes item gains in a hypermnesic task (Klein et al., 1989) and that there are age differences in relational but not item-specific encoding (Luszcz et al., 1990). This information provided the basis for three predictions: (a) There are age differences in hypermnesia, (b) there are age differences in word losses in a hypermnesic task, and (c) there are no age differences in word gains in a hypermnesic task. In order to manipulate type of encoding, a list of words with high association strength (to evoke relational encoding) and words with low association strength (to evoke item-specific encoding) was constructed. The results of this investigation provide support for the encoding manipulation and for all three predictions. In addition, the nature of the age differences in word loss observed suggests that although older adults may be capable of relational encoding, this form of encoding is not as effective at preventing word loss for them as it is for younger adults.

Adult↗