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Biomedical subjects

J P Spire

Publications and source records attributed to J P Spire.

At least 19 recordsLinked to original sources
PubMed1992

Hypoglycemic thresholds for cognitive dysfunction in IDDM.

Fourteen poorly controlled insulin-dependent diabetes mellitus (IDDM) patients (HbA1c 11 +/- 0.5%) with a mean +/- SE duration of disease of 15 +/- 2 yr were studied to evaluate the hypoglycemic threshold for cognitive dysfunction under insulin-induced hypoglycemia. The P300 event-related potential, a measure of cognitive function, and reaction time (RT) in response to visual stimuli under euglycemic conditions and at plasma glucose concentrations of 3.5 and 2.5 mM (63 and 45 mg/dl, respectively) during a constant insulin infusion were recorded. Baseline P300 latency was similar to that of a nondiabetic control group, but baseline RT was greater in the IDDM group. There was no increase in P300 latency or RT under euglycemic clamp conditions or at a plasma glucose level of 3.5 mM (63 mg/dl). However, when plasma glucose was lowered to 2.5 mM (45 mg/dl), there was an increase in P300 latency and a prolongation of RT. As plasma glucose returned to baseline, P300 latency and RT remained prolonged. After administration of intravenous glucose and a meal, P300 latency and RT returned to baseline. P140, an event-related potential reflecting sensory processes, was not altered. Because P300 latency changes paralleled RT changes, hypoglycemia appears to slow decision-making processes in IDDM. This study revealed that 1) baseline P300 latency is not elevated in poorly controlled IDDM patients, suggesting no cumulative cognitive dysfunction.

Blood Glucose↗
PubMed1991

Modulation of glucose regulation and insulin secretion by circadian rhythmicity and sleep.

To define the roles of circadian rhythmicity (intrinsic effects of time of day independent of the sleep or wake condition) and sleep (intrinsic effects of the sleep condition, irrespective of the time of day) on the 24-h variation in glucose tolerance, eight normal men were studied during constant glucose infusion for a total of 53 h. The period of study included 8 h of nocturnal sleep, 28 h of continuous wakefulness, and 8 h of daytime sleep. Blood samples for the measurement of glucose, insulin, C-peptide, cortisol, and growth hormone were collected at 20-min intervals throughout the entire study. Insulin secretion rates were derived from C-peptide levels by deconvolution. Sleep was polygraphically monitored. During nocturnal sleep, levels of glucose and insulin secretion increased by 31 +/- 5% and 60 +/- 11%, respectively, and returned to baseline in the morning. During sleep deprivation, glucose levels and insulin secretion rose again to reach a maximum at a time corresponding to the beginning of the habitual sleep period. The magnitude of the rise above morning levels averaged 17 +/- 5% for glucose and 49 +/- 8% for calculated insulin secretion. Serum insulin levels did not parallel the circadian variation in insulin secretion, indicating the existence of an approximate 40% increase in insulin clearance during the night. Daytime sleep was associated with a 16 +/- 3% rise in glucose levels, a 55 +/- 7% rise in insulin secretion, and a 39 +/- 5% rise in serum insulin. The diurnal variation in insulin secretion was inversely related to the cortisol rhythm, with a significant correlation of the magnitudes of their morning to evening excursions. Sleep-associated rises in glucose correlated with the amount of concomitant growth hormone secreted. These studies demonstrate previously underappreciated effects of circadian rhythmicity and sleep on glucose levels, insulin secretion, and insulin clearance, and suggest that these effects could be partially mediated by cortisol and growth hormone.

Adult↗
PubMed1991

Cortical asymmetry of REM sleep EEG following unilateral pontine hemorrhage.

A 24-year-old woman with a left pontine hematoma showed marked asymmetry in the EEG of REM sleep, suggesting that a unilateral pontine lesion is sufficient to disrupt normal REM sleep EEG in the ipsilateral hemisphere. Other REM sleep characteristics (rapid eye movements, muscle atonia) were unaffected by this lesion.

Adult↗
PubMed1990

Hypoglycemic thresholds for cognitive dysfunction in humans.

Nineteen healthy adult volunteers were studied to define the nature of and threshold for the cognitive dysfunction that occurs during insulin-induced hypoglycemia. The P300 cerebral event-related potential is an electrophysiological correlate of cognitive decision-making processes that can be measured in response to either an auditory or visual stimulus. P300 and reaction time (RT) were recorded from a visual stimulus under euglycemic conditions and at plasma glucose concentrations of 3.3 and 2.6 mM during insulin infusion in 10 subjects. Reducing plasma glucose levels to 3.3 mM was not associated with an increase in either the latency or amplitude of the P300 component or a change in RT. However, further lowering of plasma glucose to 2.6 mM resulted in an increase in the latency of P300 and a prolongation in RT. Similar changes were seen for the auditory P300 in experiments performed on 9 additional subjects in which both auditory and visual stimuli were presented. The prolongation of P300 did not correct immediately when plasma glucose was raised to basal levels with intravenous glucose but returned to normal 45-75 min later, after ingestion of a carbohydrate-containing meal. Analysis of another event-related potential, P140 (a measure of the sensory processes), showed no change in response to hypoglycemia. Prolongation of RT paralleled the prolongation of P300 latency, suggesting that motor processes were not altered. Therefore, hypoglycemia appears to induce abnormalities in decision-making processes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Three-dimensional magnetic resonance images of the brain: application to neurosurgical planning.

Data from single 10-minute magnetic resonance scans were used to create three-dimensional (3-D) views of the surfaces of the brain and skin of 12 patients. In each case, these views were used to make a preoperative assessment of the relationship of lesions to brain surface structures associated with movement, sensation, hearing, and speech. Interactive software was written so that the user could "slice" through the 3-D computer model and inspect cross-sectional images at any level. A surgery simulation program was written so that surgeons were able to "rehearse" craniotomies on 3-D computer models before performing the actual operations. In each case, the qualitative accuracy of the 3-D views was confirmed by intraoperative inspection of the brain surface and by intraoperative electrophysiological mapping, when available.

Adolescent↗
PubMed1989

Comparison of sympathetic skin response with quantitative sudomotor axon reflex test in diabetic neuropathy.

The sympathetic skin response (SSR), the quantitative sudomotor axon reflex test (Q-SART), and cardiac beat-to-beat variability with respiration as measured by the expiratory/inspiratory ratio (E/I ratio) were studied in 39 patients with diabetic neuropathy of whom 33 also had one or more symptoms of autonomic involvement. In the lower extremities 87% of the patients with an absent SSR had an abnormal Q-SART (P less than 0.001), and 81% of patients with the SSR present had a normal Q-SART (P less than 0.02). The E/I ratio was abnormal in all but one of 23 patients with an absent SSR in the foot, and a normal E/I ratio was present only in those patients (n = 7) with the SSR present in hand and foot, and in an eighth patient who had SSR absent in the foot and present in the hand. A similar correlation was found between the E/I ratio and the Q-SART in the foot, although 4 of 25 patients with an abnormal foot Q-SART had a normal E/I ratio. We conclude that the concordance of results of the SSR and Q-SART supports the combined use of these tests to uncover early distal sympathetic failure in diabetic neuropathy.

Adult↗
PubMed1989

Hemi-field pattern visual evoked potentials: a comparison of display and analysis techniques.

Three methods for analyzing the spatial organization of visual evoked potentials were compared. Pattern reversal visual evoked potentials were obtained from a single subject under three viewing conditions: stimulation of the left, right, and both visual fields. The scalp distribution of the VEP to 1 deg checks was displayed using three recording and analysis techniques: a conventional horizontal occipital array of electrodes, topographic mapping, and 3-dimensional evoked potentials. All three techniques revealed "paradoxical" lateralization of P100. The relative merits of each technique are discussed.

Brain Mapping↗
PubMed1989

Electrophysiologic studies on locked-in patients: heterogeneity of findings.

Somatosensory evoked potentials, brain-stem auditory evoked potentials and electroencephalograms were obtained from 9 patients with the diagnosis of 'locked-in' syndrome. No pattern of evoked potential abnormality was specific to this syndrome, with findings ranging from bilaterally normal to unilaterally or bilaterally absent. The evoked potential studies complemented radiographic findings in defining the extent of the lesion and revealed that a portion of the pontine tegmentum was usually involved. Pathology from 2 patients corroborated the findings of the evoked potential studies. The value of evoked potential studies of patients with locked-in syndrome is to provide early objective evidence of brain-stem involvement independent of the clinical examination, EEG and radiographic studies.

Adult↗
PubMed1989

Vector analysis of three-dimensional evoked potentials: eccentric dipoles.

The quantitative description of three-dimensional cerebral evoked potentials is extended to include eccentric dipolar sources. Eccentricity-related distortions in dipole orientation and magnitude are assessed. The use of nonstandard montages, the prediction of topographic surface maps, dynamic analysis, and theoretical mechanisms of planar segment formation are discussed.

Brain↗
PubMed1989

Inter- versus intra-subject variance in topographic mapping of the electroencephalogram.

The variability of the normal topographic EEG distribution between a quiet, eyes closed, resting state and the performance of cognitive tasks (listening to a story or music) was studied in 20 normal (10 male) right-handed college students or graduates ages 18-40 yrs. Amplitude changes in the topographic frequency distribution (2.5-7 SD) of alpha frequency band (8-13 Hz) were noted between tasks and resting state in individual subjects. When group data for the resting versus listening states were compared, no statistical differences could be demonstrated. The group variability was 50% of the power of the resting record. Repeat studies in 10 subjects demonstrated a test-retest variance of 10% of the mean individual power. The data suggest that inter-subject differences in the alpha frequency and individual topographic differences will require careful normalization for development of baseline "brain maps" to serve as a standard for investigation of disease states.

Adult↗
PubMed1988

The Landau-Kleffner syndrome of acquired epileptic aphasia: unusual clinical outcome, surgical experience, and absence of encephalitis.

The syndrome of acquired verbal auditory agnosia in childhood with mutism and epileptic discharges has been described in over 100 cases. An encephalitic etiology has often been postulated but never proved. We report two patients with this syndrome who were treated surgically. Despite careful search, no pathologic evidence of encephalitis was found. One patient, with the typical course, had no seizures but striking positive correlation between epileptic discharge and language disorder; the second, after classic onset, developed intractable temporal lobe epilepsy, a previously unreported outcome of this syndrome. EEG discharges are generalized, bilateral, multifocal, or with shifting predominance but mainly temporal in 85% of reported cases, and unilateral, also predominantly temporal, in 15%. Language areas are preferentially involved. This syndrome has certain biologic features that resemble the benign epilepsies of childhood and may be the result of the unusual localization of the epileptic abnormality.

Adult↗
PubMed1987

Sympathetic skin response in diabetic neuropathy.

The sympathetic skin response (SSR) was studied in 47 diabetic patients selected for the presence of symptoms and clinical signs of peripheral neuropathy and in 24 normal control subjects. The SSR was present in all controls but was absent at the foot in 66% and at the hand in 27.7% of the diabetic patients. Absence of the SSR failed to correlate with other electrophysiologic parameters on routine nerve conduction and electromyographic studies. Although absent SSR was more often found in patients with symptoms of autonomic dysfunction (P less than 0.05), there was no correlation with any specific symptoms of autonomic involvement. The SSR was frequently absent, at least in the foot, in those patients with abnormal cardiac beat-to-beat variability (expiratory: inspiratory, E:I, ratio) and pupil cycle time (PCT). In addition there was a good correlation between the amplitude of the SSR and the value of the E:I ratio (r = 0.81, P less than 0.001). The SSR may be a valuable adjunct in the assessment of autonomic involvement in diabetic neuropathy, but its sensitivity requires further evaluation.

Adult↗
PubMed1976

Visually evoked response. Use in neurologic evaluation of posttraumatic subjective visual complaints.

Evaluation of subjective visual complaints unassociated with objective signs is a frequent problem in neurologic and ophthalmic practice. The visually evoked response (VER) is an important tool for separating the functional from the organic in patients claiming visual disturbance. In visual complaints associated with late posttraumatic epileptic activity, the VER can demonstrate an abnormality even in asymptomatic intervals. In complaints due to concussion, it demonstrates disorganized evoked responses initially and later a return of the normal resonse. It shows an abnormality in the occipital lobes during and after transient compression of the vertebral artery. A normal VER excludes all but trivial involvement of the visual system, symptomatic claims of the patient notwithstanding.

Adult↗
PubMed1976

Electroencephalographic changes following intraamniotic prostaglandin F2 alpha administration for therapeutic abortion.

Electroencephalograms were obtained on 43 patients undergoing therapeutic second trimester abortion using intraamniotic prostaglandin F2alpha. Recordings were made before and 4 hours after prostaglandin administration, as well as 4 hours after the abortion. At 4 hours after prostaglandin administration, 30% of the women had abnormal tracings, while 50% of the women had abnormal recordings 4 hours postabortion. Although the changes consisted primarily of mild generalized or lateralized slowing, 4 patients developed paroxysmal activity not initially present. This finding would seem to suggest a potential relationship between PGF2alpha administration and clinical seizures.

Abortion, Therapeutic↗
PubMed1975

Hemodialysis of phenytoin in a uremic patient.

Removal of phenytoin by hemodialysis was determined in a uremic patient. The rate of appearance of the drug in dialysate, the plasma concentration with time, and the plasma clearance by dialysis were measured. Plasma protein binding of phenytoin was also determined. In spite of greatly reduced plasma protein binding in the uremic patient, removal rate was observed to be less than 10% of the rate of presentation of the dialyzer. During the 6-hr period of dialysis, the plasma concentration showed little change. The amount collected in the dialyase, 43.6 mg, was only a small fraction of drug in the body. These results indicate that replacement of phenytoin based on the amount of drug removed by dialysis is unnecessary in chronically dialyzed uremic patients. In addition, the utility of hemodialysis in phenytoin overdose is questioned.

Adult↗
PubMed1975

Electrophysiological parameters in the evaluation of occipital apoplexy.

Visual evoked responses (VER) in four cases of occipital apoplexy supplemented perimetric diagnosis with new electrophysiologic parameters. These included diagnosis of (1) optic radiation involvement by delay in the initial VER component; (2) stirate cortical involvement by obliteration of the initial and late VER components; (3) suprastriate involvement by selective loss of the late VER components, and (4) recovery at one or more of the above levels in the visual process by follow-up examination.

Adult↗