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Biomedical subjects

R Boyle

Publications and source records attributed to R Boyle.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1991

Morphological correlates of response dynamics and efferent stimulation in horizontal semicircular canal afferents of the toadfish, Opsanus tau.

1. We used the intraaxonal labeling technique to study correlations between the terminal dendritic morphology of horizontal semicircular canal primary afferents and their response dynamics to sinusoidal head rotation and combined electrical stimulation of central efferent vestibular neurons. Thirty-eight canal afferents were identified by their sensitivity and phase of response to rotation between 0.1 and 1.0 Hz (+/- 10 degrees/s) and were subsequently labeled with horseradish peroxidase or biocytin. The afferent's dendritic field and synaptic specializations in the neuroepithelium of the crista were examined under light microscopy. 2. Rate and regularity of background discharge of the afferent were not correlated with its axon diameter or relative location of its dendritic field in the crista. 3. Response sensitivity of the afferent to rotation was correlated both with the relative location of its dendritic field in the crista and with the number of terminal endings it possesses. Afferents having low sensitivities, slow dynamics, and few terminal endings supply the peripheral portions of the crista; afferents with higher sensitivities, faster dynamics, and greater number of terminal endings supply the more central portions. It is suggested that the differences in sensitivity among the afferents reflect principally the variations in both the cupular dynamics along the crista and the number of possible hair cell contact sites in the neuroepithelium. 4. Response phase of the afferent was correlated only with the extent of its dendritic processes along the transverse axis of the crista. Afferents having transversely oriented dendritic fields had less phase lags relative to acceleration than did those having a more longitudinally oriented dendritic field. 5. Efferent stimulation produced a change in both the afferent's discharge rate and its response sensitivity to rotation. Afferents discharge rate and its response sensitivity to rotation. Afferents having a centrally located dendritic field and acceleration afferents, defined by their response to rotation, were the most affected by efferent stimulation. These results suggest that efferent innervation is either directed toward, or most efficacious in, the central regions of the crista and that it may select specific hair cell-afferent complexes.

Animals↗
PubMed1990

Detection of breast abnormalities on teleradiology transmitted mammograms.

The authors conducted an observer performance study to compare breast lesion detection of conventional mammography (CM) with teleradiology (TE) transmitted mammograms. One hundred four abnormal, single-projection mammographic images were transmitted by teleradiology. Abnormalities included 11 cases with skin thickening or retraction, 48 cases with microcalcifications, and 52 with parenchymal masses. The CM and TE images were reviewed by four mammographers who indicated the type and location of abnormalities and a level of confidence for their diagnostic decisions. For each of three detection tasks--skin and nipple abnormalities, microcalcifications, and masses--receiver operating characteristic curve analysis was performed for individual readers and all readers as a group. For detecting skin and nipple abnormalities, readers performed significantly better with CM than with TE (z = 2.05, P = less than 0.04). However, no significant differences were found among readers for detection of either microcalcifications or masses. Further improvements in hardware and imaging parameters may improve detection of soft tissue abnormalities. Further evaluation is necessary to determine whether teleradiology might be applicable to breast cancer screening.

Breast Neoplasms↗
PubMed1990

A correlation between severity of migraine and delayed gastric emptying measured by an epigastric impedance method.

1. This study examined the ability of a bioimpedance method to detect the delay in gastric emptying which occurs during attacks of migraine. 2. In 64 non-migraineur control patients and 46 migraine patients outside an attack, gastric emptying rates were within the predicted normal range. 3. In contrast, rates in 14 migraineurs during 20 attacks were delayed during severe or moderate attacks and were significantly correlated with the intensity of headache, nausea and photophobia. 4. The epigastric impedance method was generally well tolerated by patients and appears to merit further investigation as a clinical method of monitoring gastric emptying of liquids.

Adolescent↗
PubMed1990

Resting discharge and response dynamics of horizontal semicircular canal afferents of the toadfish, Opsanus tau.

The response dynamics of 66 primary afferents of the horizontal semicircular canal were studied in the toadfish using sinusoidal, rotational stimuli from 0.001-10 Hz at amplitudes of 5-100 degrees/sec. Twelve afferents were also tested to constant velocity trapezoids. Responses to sinusoids were used to classify afferents into 3 broad groups: (1) low-gain afferents that maintain a relatively linear response re: stimulus velocity across most of the frequency and amplitude spectra tested; (2) high-gain afferents that have a velocity sensitivity but also show a high-frequency gain enhancement and phase advance; and (3) so-called acceleration afferents that have a response more in phase with stimulus acceleration than velocity across the tested bandwidth. The afferent's background discharge was examined in relation to its rotational response. Low-gain afferents have regular spacing of interspike intervals. High-gain and acceleration afferents have a widely variable discharge regularity that is apparently unrelated to their rotational responses. Input/output transfer models were fit to the response data to describe the low- and high-pass filtering properties of the 3 afferent groups.

Animals↗
PubMed1990

Efferent vestibular system in the toadfish: action upon horizontal semicircular canal afferents.

The influence of the efferent vestibular system (EVS) upon the background discharge and response dynamics of horizontal semicircular canal afferents was examined in the toadfish. In one set of experiments the EVS was activated using a behavioral paradigm; in the second, electrical shocks were applied to the efferent vestibular nucleus in the brain stem. The afferent's background discharge and responses to rotation were recorded before and during efferent stimulation. Both EVS activation paradigms gave qualitatively similar results: a facilitation of the afferent's rate, while the animal was at rest or in motion, and a reduction in response sensitivity. Afferents were not affected uniformly: low-gain, velocity-sensitive afferents were weakly influenced, while high-gain and acceleration afferents having low rates were the most excited. The afferents' phase of response was unmodified by electrical EVS stimulation. In many afferents a prominent form of response nonlinearity is discharge silencing over large portions of the stimulus cycle. Efferent-evoked rate increase was often sufficient to produce a full-cycle bidirectional response. Caloric facilitation of afferent rate confirmed that the EVS-induced sensitivity decrease was rate independent. These results show a dual action of the efferent system: (1) facilitating the afferent's rate and (2) reducing its sensitivity to adequate stimulation that may be correlated with the dual EVS synaptic innervation of the labyrinth, namely postsynaptic efferent-afferent synapses and presynaptic efferent-hair cell synapses.

Animals↗
PubMed1988

Neuronal activity in the flocculus of the alert monkey during sinusoidal optokinetic stimulation.

1. Activity of single units was recorded in the flocculus of alert, behaving monkeys during sinusoidal optokinetic (0.02-5.0 Hz), constant velocity optokinetic, vestibular and visual-vestibular conflict stimulation. The maximal stimulus velocity for sinusoidal optokinetic stimulation at different frequencies was 40 deg/s or less (at frequencies above 1 Hz). For an amplitude series at 0.2 Hz, stimulus velocity was varied between +/- 10 to +/- 80 deg/s. In one trained monkey activity was also investigated during smooth pursuit eye movements and suppression of the vestibulo-ocular reflex by visual fixation (VOR-supp.). Only neurons which responded to 0.2 Hz (+/- 40 deg/s) optokinetic stimulation were included in the study. 2. The majority of neurons (44 out of 59) were type I Purkinje cells (PCs), which increased their simple spike activity during optokinetic cylinder rotation to the ipsilateral recording side. The responses during other, vestibular related, paradigms allowed all these neurons to be classified as so called 'gaze velocity' PCs. Three type II PCs were encountered, which responded similarly, but were only weakly modulated. 3. All type I PCs were modulated at frequencies of sinusoidal optokinetic stimulation between 0.05 and 2.5 Hz. PC's showed little or no modulation at 0.03 and 0.02 Hz. About half of the PC's still responded at 5.0 Hz. 4. Relative to eye velocity, the PC activity had a phase advance of about 30 deg between 0.1 and 2 Hz. It became larger at lower, and smaller at higher, frequencies. Eye velocity related sensitivity (imp/s/deg/s) was small at low stimulus frequencies and increased monotonically, on average from 0.16 at 0.02 Hz to 2.0 at 3.3 Hz. 5. Ten (out of 12) mossy fiber related input neurons were classified as visual neurons, since their activity could be related to the amount of retinal slip in all conditions. Neurons were clearly modulated at sinusoidal optokinetic stimulation up to 5 Hz. One input neuron, investigated during sinusoidal OKN, smooth pursuit eye movements, VOR and VOR-supp., behaved qualitatively like a 'gaze velocity' PC. The remaining input neuron encoded eye velocity at 0.2 Hz optokinetic, vestibular and visual-vestibular conflict stimulation. 6. The results show that during sinusoidal and constant velocity optokinetic stimulation 'gaze velocity' PC's do not encode eye velocity and/or eye acceleration. 7. The vestibular nuclei-flocculus complementary hypothesis (Waespe and Henn 1981) can explain PC responses to a large extent.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1988

Acute headache.

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Adult↗
PubMed1986

Assessment of the effect of nifedipine on myocardial ischaemia by using the ST segment/heart rate slope.

Nifedipine is used in patients with stable angina of effort and any resulting change in symptoms is attributed to several effects of nifedipine. However, there have been indications in such patients that one effect of nifedipine could be an increase in the severity of myocardial ischaemia, and the present report involves a trial the results of which could explain this effect. In the present trial, the effect of nifedipine on myocardial ischaemia was assessed by using the maximal ST/heart rate slope. This slope was used as an index of myocardial ischaemia because, in our hands in patients with angina, an increase or a decrease in the value of the slope respectively indicated an increase or a decrease in the severity of myocardial ischaemia as assessed by coronary arteriography. The maximal ST/heart rate slope was obtained at least twice in each of 23 patients with stable angina, with and without nifedipine; two patients were examined twice and three other patients were examined after an increased dose. Nifedipine resulted in an increase in the slope in 24 of the 28 comparisons, no change in three and a decrease in one comparison; there was a statistically significant (P less than 0.005; n = 28; paired t-test) increase in the maximal ST/heart rate slope. A further increase in the slope was obtained by increasing the dose of nifedipine in two out of three patients. The increase in the maximal ST/heart rate slope occurred in the absence of any effect of nifedipine on the initial level of ST segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Ambulatory surgery.

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Ambulatory Surgical Procedures↗
PubMed1985

Vestibular nuclei activity and eye movements in the alert monkey during sinusoidal optokinetic stimulation.

In the alert monkey (Macaca fascicularis) vestibular nuclei neurons and eye movements were recorded during sinusoidal optokinetic stimulation in the horizontal plane at frequencies between 0.02-3.3 Hz. Maximal stimulus velocity was generally kept constant at 40 deg/s, except for frequencies above 1 Hz. Eye movements showed a nystagmus-like pattern up to 0.2 Hz with a gain (change in eye position/change in cylinder position) greater than 0.8; at frequencies above 1 Hz the gain dropped to 0.35 at 3.3 Hz. A decrease in gain was accompanied by an increasing phase lag. Recordings in the vestibular nuclei were obtained from 'vestibular only' and 'vestibular plus saccade' neurons. Neurons with a strong eye position signal ('vestibular plus position') were excluded. The vast majority (87%) of neurons were not modulated at 0.2 Hz or higher frequencies of sinusoidal optokinetic stimulation, and were classified as 'low-frequency' type neurons. Compared to the response at constant stimulus velocity, sensitivity (imp X s-1/deg X s-1) dropped to 72% at 0.03 Hz and 16% at 0.1 Hz. A few neurons (13%) responding at 0.2 Hz (sensitivity on average 65% of the constant velocity response) were classified as 'high-frequency' type neurons. They did not respond above 1.0 Hz and showed no modulation with individual eye movements. The results suggest that the activity in the groups of vestibular nuclei neurons tested here is insufficient to account for the eye movements in response to sinusoidal optokinetic stimulation at frequencies above 0.1 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Pre-excitation due to accessory sinoventricular connexions associated with coronary sinus aneurysms. A report of two cases.

Ventricular pre-excitation occurred in two cases in which the accessory pathways between the atria and the ventricles were histologically identified as being associated with aneurysmal malformations of the coronary sinus. In one case the connexions were in the posterior wall of the coronary sinus aneurysm and were not related to the atrioventricular annulus; in the other, a connexion was situated in the anterior wall of the aneurysm in close apposition to the annulus and superficially resembled a Kent fibre. These connexions were considered to be of sinus venosus origin and to represent a modification of the muscular sheath that normally surrounds the coronary sinus but does not continue along the coronary veins. One of the posterior wall connecting bundles was composed of abnormally large Purkinje-like fibres; this may have played some role in the manifestation of the pre-excitation by reducing any mismatch impedance.

Adolescent↗
PubMed1984

Discharge activity of spindle afferents from the gastrocnemius-soleus muscle during head rotation in the decerebrate cat.

The activity of spindle afferents originating from both primary and secondary endings of the isometrically extended (6-8 mm) gastrocnemius-soleus (GS) muscle was recorded in precollicular decerebrate cats during sinusoidal head rotation about the longitudinal axis above a stationary body. In the first group of experiments to test the influence of vestibular volleys on fusimotor neurons, an acute bilateral neck deafferentation at C1-C3 was performed to eliminate possible influences arising from neck receptors; head rotation (0.026 Hz, +/- 15 degrees) induced a weak periodic rate modulation in 6/38 (15.8%) of the tested spindle afferents; the average response gain was 0.18 +/- 0.12, SD imp./s/deg (mean firing rate, 18.9 +/- 2.8 imp./s), and the average phase angle was -43.2 +/- 47.0 degrees, SD lag with respect to ipsilateral side-down displacement of the head (alpha-response pattern). In a second group of experiments head rotation studied after acute bilateral section of VIII cranial nerve, thereby stimulating only neck receptors, failed to influence in a reliable manner the firing rate of 38 additional spindle afferents. In a third group of experiments in which both VIII nerves and cervical dorsal roots were left intact, head rotation induced a response in 7/45 (15.6%) of the tested spindle afferents similar to that observed after cervical deafferentiation and thus depended on stimulation of labyrinth receptors alone. Over the examined frequency range of head rotation from 0.015 to 0.325 Hz (+/- 15 degrees), the response gain of spindle afferents was relatively stable during sinusoidal labyrinth stimulation. For most of the spindle afferents the phase angle of the response elicited at the lower frequencies was related to the direction of head orientation towards the ipsilateral sidedown, thus being attributed to labyrinth volleys originating from macular receptors; at 0325 Hz the stimulus was less effective and some units showed a phase advance relative to head position which was attributed to costimulation of canal receptors. Displacement of the muscle under study obtained by either rotation of the whole animal or body alone beneath a stationary head elicited a periodic modulation of spindle afferent discharge, independent of head orientation or type of preparation, in 51/73 (70%) of the muscle spindles tested; the average response gain was 0.20 +/- 0.19, SD imp./s/deg, and an average phase lead of +14.1 +/- 20.5 degrees, SD with respect to the peak of the ipsilateral side-down displacement of the body or of the animal was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗