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Biomedical subjects

R Boyle

Publications and source records attributed to R Boyle.

At least 37 records · Page 2Linked to original sources
PubMed1996

Effects of irrelevant sounds on phonological coding in reading comprehension and short-term memory.

The effects of irrelevant sounds on reading comprehension and short-term memory were studied in two experiments. In Experiment 1, adults judged the acceptability of written sentences during irrelevant speech, accompanied and unaccompanied singing, instrumental music, and in silence. Sentences varied in syntactic complexity: Simple sentences contained a right-branching relative clause (The applause pleased the woman that gave the speech) and syntactically complex sentences included a centre-embedded relative clause (The hay that the farmer stored fed the hungry animals). Unacceptable sentences either sounded acceptable (The dog chased the cat that eight up all his food) or did not (The man praised the child that sight up his spinach). Decision accuracy was impaired by syntactic complexity but not by irrelevant sounds. Phonological coding was indicated by increased errors on unacceptable sentences that sounded correct. These errors rates were unaffected by irrelevant sounds. Experiment 2 examined effects of irrelevant sounds on ordered recall of phonologically similar and dissimilar word lists. Phonological similarity impaired recall. Irrelevant speech reduced recall but did not interact with phonological similarity. The results of these experiments question assumptions about the relationship between speech input and phonological coding in reading and the short-term store.

Adolescent↗
PubMed1996

Determinants of semicircular canal afferent response dynamics in the toadfish, Opsanus tau.

1. Present results determine the relative contributions of the biomechanical and the posttransduction-current (PTC) mechanisms to the sensory process carried out by the horizontal semicircular canal (HC) in the oyster toadfish, Opsanus tau. The role of each element was estimated using in vivo measurements of hair cell receptor potentials and afferent responses elicited by electrical stimuli and mechanical HC indentation. Individual afferent response dynamics are defined here using first-harmonic transfer functions presented in the form of response gain and phase for sinusoidal stimuli from approximately 0.02-30 Hz. Comparison of the response dynamics for the two types of stimuli distinguishes the mechanical and the PTC transfer functions leading to the neural response. The results show that both mechanisms contribute significantly to the overall signal processing performed by the semicircular canals. 2. Endolymphatic polarization and HC indentation. Modulation of the endolymphatic potential by current injection induces a differential voltage across the apical face of the hair cells that drives the transduction current directly via the Nernst-Planck potential. Results show that the electrical impedance of the apical tight junctions is much larger than the basal impedance to ground in O. tau, such that leakage current to the basolateral space is negligible and the voltage-sensitive basolateral currents remain fully functional during polarization of the endolymph (in the frequency range tested). Extracellular afferent responses to endolymphatic polarization were combined with responses to HC indentation to separate the relative contributions of the mechanical and the PTC mechanisms to the overall afferent response dynamics. Data show that more than one-half of the overall signal processing, as defined by the first-harmonic transfer function, persists even when canal mechanics is bypassed. 3. Hair-cell receptor potential modulation during HC indentation. Sharp microelectrodes were used to record the modulation of hair-cell receptor potentials (intracellular voltages) in vivo during physiological levels of sinusoidal HC indentation. Receptor potentials exhibit modulations dominated by the first harmonic and centered about the resting potential. The average gain of the receptor-potential modulation for HC indentation is approximately 0.88 mV/microns indent, corresponding to a value of 0.22 mV/deg/s head velocity, centered near zero phase over the range tested from 0.1-10 Hz. The present receptor potential data fall well short of spanning the full range of gain and phase present in the afferent population. Rather, intracellular hair-cell responses are consistent with the frequency-dependent mechanical activation of the transduction current as determined above. 4. Origins of individual afferent responses. The population of afferent responses forms a continuous distribution that is discussed here in terms of three groups as defined by Boyle and Highstein: velocity-sensitive low gain (LG) afferents, velocity/acceleration-sensitive high gain (HG) afferents, and acceleration-sensitive (A) afferents. The response dynamics of individual afferents were found to be determined by a mix of biomechanical and biophysical factors that vary systematically between these afferent groups. All afferents show low-frequency phase advancement and gain decrease during HC indentation associated with the mechanical lower-corner frequency and high-frequency phase and gain enhancements associated with the PTC processing. In highly phase-advanced afferents (A type), the mechanical response is additive with the PTC processing to achieve broad-band acceleration sensitive neural responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Fatal familial insomnia: a seventh family.

A 60-year-old woman with a typical history of fatal familial insomnia (FFI) had FFI proven by histologic examination and molecular testing. Her son, who died at the age of 20 in 1978, had a rapidly progressive dementing illness without reported insomnia. He carried the characteristic mutation for FFI and is the youngest patient reported with this condition.

Adult↗
PubMed1995

Mechanical indentation of the vestibular labyrinth and its relationship to head rotation in the toadfish, Opsanus tau.

1. In the present study we examine the response of the semicircular canal of the toadfish (Opsanus tau) to head rotation and to mechanical indentation of the membranous labyrinth. The relationship between the two stimuli is described by a new elastohydrodynamic model that delineates the three-dimensional (3-D) spatiotemporal distribution of endolymph pressure and flow. In vivo electrophysiological recordings of primary afferents supplying the horizontal canal (HC) were employed to validate the model predictions. Data were collected from 213 afferents in 18 fish during independent head rotation. HC indentation, utricle (U) indentation, and paired stimuli. To quantify the afferent response and the relationship between the applied sinusoidal stimuli, the magnitude (gain) and temporal relationship (phase) of the first harmonic of modulation were calculated and compared with theoretical predictions. 2. A mathematical based extensively on the 3-D morphology of a toadfish labyrinth and the physical properties of endolymph is presented to describe the relationship between head rotation and mechanical indentation. All model parameters specifying labyrinthine morphology and physical properties of endolymph are known; the model contains no free parameters. New results are independent of the structural properties of the cupula. The analysis employs an asymptotic solution of the Navier-Stokes equations in the three toroidal ducts that includes the 3-D fluid-structure interaction taking place within the enlarged ampulla. The solution addresses the differential pressure (delta P) acting across the cupula and the dilatational pressure acting on both sides of the cupula. The analysis quantifies the hydrodynamics of the HC for mechanical indentations of the long and slender portion of the canal duct (HC indentation) and the U (U indentation). Results specifically relate the indentation stimuli to head rotation. Linear commutations of HC indentation, U indentation, and rotation stimuli are analyzed by matching delta P acting across the cupula for the three stimulus modalities. 3. HC afferents show a linear correspondence between HC indentation, U indentation, and rotation stimuli. Specific experimental results for sinusoidal stimuli at frequencies < 2 Hz show 1) +/- 1 micron-HC indentation commutates with +/- 4 degrees/s rotation, 2) + 1-micron HC indentation commutates with -/+ 15-microns U indentation, and 3) -/+ 15-microns U indentation commutates with +/- 4 degrees/s rotation. These results were obtained by adjusting the relative amplitude and phase of two stimuli presented simultaneously to achieve destructive interaction that minimizes the afferent modulation (balanced). Equivalent results were obtained using afferent responses to the stimuli applied independently.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1995

The relationship between calcium, phosphorus, and sodium intake, race, and blood pressure in children with renal insufficiency: a report of the Growth Failure in Children with Renal Diseases (GFRD) Study.

Nutritional data compiled during the Growth Failure in Children with Renal Diseases Clinical Trial were analyzed to determine the relationship between the dietary intake of divalent minerals and sodium, nutritional status, and serum calcium, phosphorus, and parathyroid hormone (PTH) concentrations and blood pressure in black versus white children. One hundred eighteen patients are included in this report; 25 were black (21%) and 93 were white (79%). Although more of the blacks were male, the age distribution, midarm circumference, midarm muscle circumference, blood pressure, and serum calcium, phosphorus, and PTH concentrations were comparable in the two groups. Phosphorus intake was within the recommended daily allowance in both groups; in contrast, calcium intake was inadequate in all patients: 81% of the recommended daily allowance in whites, and 74% in blacks. Sixteen children were noted to be hypertensive during the observation period; six patients were receiving a variety of antihypertensive medications, including diuretics in two children. Linear regression analysis revealed that systolic and diastolic blood pressures were directly related to calcium and phosphorus intake in black patients. In white children, only dietary phosphorus intake and diastolic blood pressure were directly related. There was no relationship between sodium intake or GFR and blood pressure in the white or black children. PTH levels were directly correlated with systolic and diastolic blood pressure in all children. The correlations between PTH and blood pressure were stronger in white versus black patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Black People↗
PubMed1995

Familial periodic cerebellar ataxia without myokymia maps to a 19-cM region on 19p13.

Familial periodic cerebellar ataxia (FPCA) is a heterogeneous group of rare autosomal dominant disorders characterized by episodic cerebellar disturbance. A potassium-channel gene (KCNA1) has been found to be responsible for one of its subgroups, familial periodic cerebellar ataxia with myokymia (FPCA/+M; MIM 160120). A different subgroup that is not associated with myokymia (FPCA/-M; MIM 108500) was recently mapped to chromosome 19p. Here we have performed linkage analysis in two large families with FPCA/-M that also demonstrated neurodegenerative pathology of the cerebellum. Three markers in 19p13 gave significant lod scores (> 3.0), while linkage to KCNA1 and three known loci for spinocerebellar ataxia (SCA1, SCA2, and SCA3) was excluded. The highest lod score was obtained with the marker D19S413 (4.4 at recombination fraction 0), and identification of meiotic recombinants in affected individuals placed the locus between the flanking markers D19S406 and D19S226, narrowing the interval to 19 cM. A CAG trinucleotide-repeat expansion was detected in one family but did not cosegregate with the disease.

Cerebellar Ataxia↗
PubMed1994

Long-term evaluation of treatment for chronic heart failure: a 1 year comparative trial of flosequinan and captopril.

Two hundred and nine patients with moderate to severe chronic heart failure, all of whom remained symptomatic despite at least 80 mg of frusemide daily, were randomized to 12 months treatment with flosequinan or captopril. The patients were stratified into two groups, a treadmill group and a corridor walk test group, depending upon their exercise capability. Sixty-five out of 102 patients randomized to flosequinan and 43 out of 107 randomized to captopril (p < 0.001) did not complete the study. There was no difference between the groups in mortality: 19 patients died while taking flosequinan and 15 while taking captopril. Both drugs had similar effects on treadmill exercise tolerance; the mean increase at week 52 was 117 seconds in the flosequinan group and 156 seconds (p = 0.57) for the captopril group. For those patients stratified to the corridor walk test only, there was also very little difference in the improvement at 52 weeks; the mean increase for patients randomized to flosequinan was 61 meters and captopril was 75 meters (p = 0.65). However, when the walk tests from all patients are examined, captopril produced a significant improvement compared with flosequinan at week 52 (p = 0.015). Flosequinan has similar long-term efficacy to captopril but is associated with a higher incidence of adverse events.

Blood Pressure↗
PubMed1994

Sensory transduction of head velocity and acceleration in the toadfish horizontal semicircular canal.

1. Sinusoidal mechanical indentation of the long-and-slender limb of the horizontal semicircular canal and/or utricle was used to produce adequate stimulation of the labyrinth. Indentation of the canal increased, while indentation of the utricle decreased the afferent discharge rate. This follows because indentation of the canal and utricle produce oppositely directed mechanical stimuli as defined by endolymph flow, transcupular pressure, and cupular deflection. Simultaneous in-phase indentations of both the canal and utricle, with amplitudes adjusted to produce equal (but opposite) magnitudes of afferent response modulation, generate destructive interaction that minimizes the afferent modulation, whereas sinusoidal indentation 180 degrees out-of-phase generates constructive interaction that maximizes the afferent modulation. This observation correlates directly with analysis of the labyrinthine elasto-hydrodynamics which predicts that balanced in-phase indentations minimize macromechanical endolymph flow through the ampullary cross section and maximize the dilatational pressure within the ampulla acting equally on both sides of the cupula and across the labyrinthine wall. 2. Two groups of afferents are identified according to their response to balanced sinusoidal indentation of the canal limb and the utricle. In one group there is complete destructive interaction and the afferent response can be effectively nulled by adjusting the relative amplitude and phase of the two stimuli. In the second group a residual afferent response remains that cannot be nulled. The residual is described in the model as unit-specific sensitivity to dilatational pressure acting equally on both sides of the cupula.

Afferent Pathways↗
PubMed1993

Caesarean section anaesthesia and the Apgar score.

Retrospective comparison of epidural and general anaesthesia by a multivariate analysis of 1 and 5 minute Apgar scores did not show that general anaesthesia improves operating conditions for Caesarean section or reduces fetal trauma for preterm and term infants.

Analysis of Variance↗
PubMed1993

Activity of medial vestibulospinal tract cells during rotation and ocular movement in the alert squirrel monkey.

1. Chronic unit and eye movement recording and microstimulation techniques were used to study the discharge properties of identified medial vestibulospinal tract (MVST) cells in the alert squirrel monkey. MVST cells were antidromically activated from the ventromedial funiculus at C1 and responded to orthodromic stimulation of the ipsilateral VIIIth nerve (Vi) at mono- or disynaptic latencies. Cell discharges were examined during imposed sinusoidal yaw rotation to activate horizontal semicircular canal afferents and during voluntary ocular pursuit and fixation of visual targets with the head held stationary. 2. MVST cells represented 15% (22 of 147 cells) of the population of horizontal canal-related cells recorded in the vestibular nuclei. Twelve MVST cells were monosynaptically related to Vi; of these cells, 7 (58%) were characterized as ipsilateral eye and head velocity, having a discharge modulation related to the velocity of both ipsilaterally directed eye movement and yaw rotation, and 3 also had an ipsilateral eye position sensitivity. Most (8 of 10, 80%) MVST cells disynaptically related to Vi responded only to contralateral head velocity; the other 2 cells carried a combined contralateral head and ipsilateral eye movement signal. A pause or burst of discharge associated with fast or saccadic eye movements made in any direction was not present on the 22 MVST cells. 3. The MVST is an output pathway of the vestibular nuclei through which the labyrinth controls reflex head movements. The results show that MVST cells transmit the movement and position of eyes in orbit, with vestibular signals, to the cervical spinal cord and suggest that the MVST may play a dynamic role in voluntary gaze stabilization and eye/head tracking.

Animals↗
PubMed1993

A case of Guillain-Barré syndrome with focal segmental glomerulosclerosis.

Acute inflammatory polyneuropathy or Guillain-Barré syndrome may be associated with glomerulonephritis, especially membranous nephropathy. This paper details the case of a 73-year-old woman presenting with acute onset of Guillain-Barré syndrome associated with an abnormal urinary sediment and significant proteinuria. Renal biopsy was consistent with focal segmental glomerulosclerosis. Despite an initial response to plasmapheresis, the patient's polyneuropathy deteriorated and subsequently improved with corticosteroid therapy. Simultaneously, her proteinuria and urinary sediment also improved. This implies that this was not a chance association. A brief discussion of the association between Guillain-Barré syndrome and glomerulopathies is undertaken.

Aged↗
PubMed1992

Inputs from regularly and irregularly discharging vestibular nerve afferents to secondary neurons in squirrel monkey vestibular nuclei. III. Correlation with vestibulospinal and vestibuloocular output pathways.

1. A previous study measured the relative contributions made by regularly and irregularly discharging afferents to the monosynaptic vestibular nerve (Vi) input of individual secondary neurons located in and around the superior vestibular nucleus of barbiturate-anesthetized squirrel monkeys. Here, the analysis is extended to more caudal regions of the vestibular nuclei, which are a major source of both vestibuloocular and vestibulospinal pathways. As in the previous study, antidromic stimulation techniques are used to classify secondary neurons as oculomotor or spinal projecting. In addition, spinal-projecting neurons are distinguished by their descending pathways, their termination levels in the spinal cord, and their collateral projections to the IIIrd nucleus. 2. Monosynaptic excitatory postsynaptic potentials (EPSPs) were recorded intracellularly from secondary neurons as shocks of increasing strength were applied to Vi. Shocks were normalized in terms of the threshold (T) required to evoke field potentials in the vestibular nuclei. As shown previously, the relative contribution of irregular afferents to the total monosynaptic Vi input of each secondary neuron can be expressed as a %I index, the ratio (x100) of the relative sizes of the EPSPs evoked by shocks of 4 x T and 16 x T. 3. Antidromic stimulation was used to type secondary neurons as 1) medial vestibulospinal tract (MVST) cells projecting to spinal segments C1 or C6; 2) lateral vestibulospinal tract (LVST) cells projecting to C1, C6; or L1; 3) vestibulooculo-collic (VOC) cells projecting both to the IIIrd nucleus and by way of the MVST to C1 or C6; and 4) vestibuloocular (VOR) neurons projecting to the IIIrd nucleus but not to the spinal cord. Most of the neurons were located in the lateral vestibular nucleus (LV), including its dorsal (dLV) and ventral (vLV) divisions, and adjacent parts of the medial (MV) and descending nuclei (DV). Cells receiving quite different proportions of their direct inputs from regular and irregular afferents were intermingled in all regions explored. 4. LVST neurons are restricted to LV and DV and show a somatotopic organization. Those destined for the cervical and thoracic cord come from vLV, from a transition zone between vLV and DV, and to a lesser extent from dLV. Lumbar-projecting neurons are located more dorsally in dLV and more caudally in DV. MVST neurons reside in MV and in the vLV-DV transition zone.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Spinal sensory radiculopathy due to Angiostrongylus cantonensis infection.

The most common cause of eosinophilic meningitis is the rat lung worm Angiostrongylus cantonensis, a parasite which is endemic in the South East Asian and Pacific regions. While the typical clinical presentation is that of meningitis associated with an eosinophilic pleocytosis, a 45 year old man presented with a radiculomyelopathy, associated with an eosinophilic pleocytosis and cerebrospinal fluid antibodies to A. cantonensis but without signs or symptoms of meningitis. A worm was demonstrated on both computed tomographic myelography and magnetic resonance imaging scan of the spinal cord.

Angiostrongylus↗