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Biomedical subjects

A Starr

Publications and source records attributed to A Starr.

At least 91 records · Page 5Linked to original sources
PubMed1995

Olfactory event-related potentials in normal human subjects: effects of age and gender.

Behavioral and electrophysiological testing of olfactory function was performed in 33 normal human male and female subjects, 18-83 years of age. Acuity for odor identification and odor detection was verified by standard psychophysical tests. For evoked potential testing, a constant flow olfactometer provided odorant stimuli (amyl acetate) or air control stimuli that were presented to the right nostril by a nasal cannula at a flow rate of 5 l/min, duration of 40 msec and random interstimulus intervals of 6-30 sec. The behavioral tests revealed no significant difference between males and females, whereas increasing age was associated with a decline in performance on the odor identification test. No reproducible evoked potentials were recorded in response to the air control stimulus. Potentials to the odorant stimulus consisted of 4 components named P1, N1, P2 and N2. A significant correlation was found between P2 latency and odor identification test scores, suggesting a relationship between the generation of the P2 component and olfactory processing. P2 peak latency increased significantly with age at 2.5 msec/year. An age-related decline in N1-P2 interpeak amplitude was seen in male subjects. Topographic differences were seen in the P2 peak amplitude and the N1-P2 and P2-N2 interpeak amplitudes such that their amplitudes were greatest at Cz and Pz. On average, N1-P2 interpeak amplitudes were larger in the female subjects than in the male subjects, possibly revealing a hormonal influence on the olfactory event-related potential.

Adolescent↗
PubMed1995

Auditory time-intensity cues in the binaural interaction component of the auditory evoked potentials.

Binaural interaction in the brainstem and middle latency auditory evoked potentials to intensity (dI) and timing differences (dT) between the two ears was studied in 10 normal hearing young adults. A component reflecting binaural interaction in the brainstem potentials occurred at approximately 7 ms and was of largest amplitude when dI and dT were 0. The latency of the binaural interaction component gradually shifted and its amplitude decreased as dI or dT increased and binaural interaction became undetectable when dI = 16 dB or when dT > or = 1.6 ms. In the middle latency potentials binaural interaction components peaking at 20, 32, and 45 ms were defined that were also largest when dI and dT = 0. The latency of the interaction did not shift with changes in dT and dI whereas the amplitude gradually decreased but binaural interaction components were still evident even at the largest values of dI (30 dB) and dT (3 ms). Psychophysical judgments of binaural perceptions showed binaural fusion of the stimuli to persist with dT values up to 1.6 ms and that lateralization of the intracranial image was complete when either dT = 1.6 ms or when dI = 16 dB. The results suggest that the presence of a binaural interaction component of auditory brainstem potentials correlates with the fusion of binaural click stimuli and the amplitude of the binaural interaction component correlates inversely with the degree of lateralization of the intracranial image. Binaural interaction components of middle latency potentials persist and continue to change even after the binaural stimuli cannot be fused.

Acoustic Stimulation↗
PubMed1995

Use of autologous umbilical artery and vein for vascular reconstruction in the newborn.

Autologous umbilical artery and vein were evaluated as vascular conduits in newborn lambs. Eight newborn lambs were delivered transabdominally under sterile conditions at term. The umbilical artery and vein were dissected from the cord and stored in culture media. On the same day, each lamb underwent bilateral superficial femoral artery transection and reconstruction. Nine arteries were reconstructed with autologous umbilical vein interposition grafts, five with umbilical artery interposition grafts, and two by primary native artery anastomosis. After the birth weight of the lambs quadrupled (37 to 45 days), they were killed and all grafts and anastomoses were examined grossly and histologically. At the conclusion of the study, both native artery anastomoses (2/2) were patent. Five umbilical vein (5/9) and two umbilical artery (2/5) autografts were also widely patent. Patent autografts retained an intact endothelium supported by a viable media. The nonpatent autografts had become atrophic remnants displaying histologic signs of early closure. Graft failures are attributed to the extreme vasoactive nature of the umbilical vessels. These preliminary results suggest that umbilical vessels may be useful as a vascular autograft if the vasoactive nature of these vessels can be overcome during the immediate perioperative period.

Anastomosis, Surgical↗
PubMed1995

Anomalous origin of right coronary artery from pulmonary artery.

A 67-year-old female was incidentally found to have an anomalous right coronary artery (RCA) arising from the pulmonary artery during evaluation of her aortic valve disease. The left main, left anterior descending, and circumflex coronary arteries were mildly dilated. Large collaterals from the left filled the RCA retrogradely. During surgery, a circumferential web was found at the ostia of the RCA. The patient underwent an aortic valve replacement, resection of the web, and translocation of the anomalous RCA into the aorta.

Aged↗
PubMed1995

EEG delta, positron emission tomography, and memory deficit in Alzheimer's disease.

Quantitative scalp EEG from 32 channels and the cerebral glucose metabolic rate from the 32 underlying cortical positions as assessed by positron emission tomography (PET) with 18F-2-deoxyglucose (FDG) were obtained on 36 patients with mild to moderate senile dementia of the Alzheimer type and 17 age- and sex-matched normal control subjects. Subjects performed a verbal memory task during uptake of FDG. There were significant correlations between both delta amplitude and metabolic rate and memory performance during FDG uptake. Patients with Alzheimer's disease had significantly greater left temporal delta amplitude and lower glucose metabolic rates. Both EEG delta in microvolts and metabolic rate had similar diagnostic sensitivity, but PET had fewer false positives among normals. The left amygdala had the highest sensitivity and percent correct diagnosis of any brain area. Temporal lobe EEG delta activity showed higher correlations with hippocampal metabolic rate than metabolic rate directly under the electrode.

Aged↗
PubMed1995

Effects of myelin or cell body brainstem lesions on 3-channel Lissajous' trajectories of fast and slow components of feline auditory brainstem evoked potentials.

Auditory brainstem evoked potentials (ABEP) were recorded from 16 awake cats using three orthogonal differential electrode pairs before and during a week after inducing neuronal lesions localized to the cochlear nucleus (CN) or the superior olivary complex (SOC), or myelin lesions localized to the fibers of the trapezoid body. ABEPs were digitally filtered to include only the slow ('pedestal') component, or only the faster first to fifth components, and three-channel Lissajous' trajectories (3CLTs) of these fast and slow components of ABEP were obtained. Cell body lesions and myelin lesions induced effects on 3CLT measures of both fast and slow components of ABEP. The results suggest a primary contribution of cell body activity to the slow component, and a primary fiber tract contribution to the fast components. However, the results do not support exclusive generation of the pedestal by cell body and dendritic post-synaptic potentials and of the faster components by action potentials along fibers. The results are consistent with a set of generators for each of the slow and fast components of ABEP, consisting of both cell bodies and their output fibers, that are spatially distributed in the brainstem.

Analysis of Variance↗
PubMed1995

Morphometric features of ruptured congenital sinus of Valsalva aneurysm: implication for surgical treatment.

Five hearts with ruptured congenital sinus of Valsalva aneurysm were studied. In 3 hearts of Caucasian patients, the sinus of Valsalva aneurysms were located in the immediate vicinity of the commissure between the noncoronary and right aortic cusps with rupture from the noncoronary sinus to the right atrium (n = 2) and from the right sinus to the right ventricle (n = 1). In 2 hearts of indigenous North Americans, the defects were sited in the immediate vicinity of the commissure between right and left aortic cusps with rupture into the right ventricle; both patients had an associated conal septal hypoplasia ventricular septal defect and aortic insufficiency. The diameters of the rupture holes at the base of the sinus of Valsalva aneurysms in the five hearts ranged from 0.4 to 1.1 cm (mean 0.7 cm). Histologic examination of longitudinal sections through the ruptured sinus of Valsalva showed 0.8 to 1.7 cm (mean 1.1 cm) wide areas in which there was lack of continuity between the aortic media and the aortic annulus. Conclusions. This study shows that the site of congenital weakness in sinus of Valsalva aneurysm in indigenous North American patients may be similar to that in Oriental patients, whereas the site tends to be different in Occidental patients. It also emphasizes the importance of patch closure rather than suture closure of ruptured sinus of Valsalva aneurysms.

Adolescent↗
PubMed1994

Interaction between endothelin and vasodilators in the human internal mammary artery.

1. The internal mammary artery (IMA) is the primary choice as an arterial graft for coronary artery bypass surgery. Endothelin (ET) has been recently measured with an increased release after cardiopulmonary bypass for coronary artery bypass grafting. Threshold concentrations of ET-1 have been found to amplify specifically contractions induced by noradrenaline and serotonin. This study was designed to investigate the effect of glyceryl trinitrate (GTN) and calcium antagonists on ET-1 contraction in the human IMA. 2. Human IMA segments taken from 21 patients undergoing IMA-coronary artery bypass grafting were mounted in an organ bath under the physiological pressure determined from their own length-tension curves. Four ring segments were allocated into four groups. One served as a control and the others were treated with GTN (10, 100 nM, or 30 microM) for 5 min or nifedipine (20 or 200 nM, or 30 microM) for 25 min before concentration-contraction curves to ET-1 were established. In separate experiments, the concentration-relaxation curves to GTN or nifedipine were established in the IMA rings precontracted with ET-1 (10 nM). 3. Pretreatment of IMA with GTN for 5 min did not alter the ET-1-induced contraction. Pretreatment with 20 or 200 nM of nifedipine slightly but not significantly, altered the maximum contraction induced by ET-1. Higher concentrations (30 microM) significantly reduced the maximum contraction force (P = 0.008). On the other hand, GTN caused 76.44 +/- 6.35% relaxation in ET-1-precontracted IMA. In contrast, the nifedipine-induced relaxation was difficult to establish due to unsustained contraction to ET-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Endothelins↗
PubMed1994

Clinical hemolysis with the St. Jude heart valve without paravalvular leak.

In 1990 and 1991 we operated on 2 patients with persistent clinical hemolysis, in the absence of perivalvular leaks, who had had their mitral valves replaced with St. Jude Medical valve (SJMV) prostheses. The valves had been implanted 14 months and 3 months before, respectively. There were no other discernible causes for the hemolysis and when each SJMV was replaced the hemolysis disappeared in that patient. The first valve was not tested in the laboratory owing to its loss, but it looked normal. The second valve was tested and found to have regurgitation well within the usual limits for this valve. Fringe pattern interferometry indicated that the leading edge of each leaflet was flatter and less smooth than that of another SJMV. Reviewing the literature we find that idiopathic, persistent clinical hemolysis in recipients of St. Jude mechanical heart valves is a rare phenomenon, which has appeared in 4 reports totaling 9 cases. We discuss the suggested mechanisms involved, and add the possibility of leading leaflet edge characteristics.

Aged↗
PubMed1994

Actuarial versus actual risk of porcine structural valve deterioration.

Actuarial analysis, using nonparametric (e.g., life table or Kaplan-Meier) or parametric (statistical modeling) methods, is used to describe and compare survival probabilities by allowing for partial survival times (censoring). Although devised to describe freedom from death, this method has been extended to nonfatal complications, such as freedom from tissue valve failure. However, the risk described for nonfatal events is that which a patient would experience provided he were immortal. And patients with valve disease have a relatively high risk of dying, generating the question: "What is the chance the valve will fail before the patient dies?" To answer this more practical (for individual patient management and population resource allocation) question requires an estimate of what we call actual failure, that is, the percentage of patients whose valve will actually fail before they die. This risk is less than the risk which the usual actuarial curve describes. This difference increases with patient age, because older patients have a lower risk of tissue failure and a higher risk of death than younger patients.

Actuarial Analysis↗
PubMed1994

Surgical repair of subaortic stenosis in atrioventricular canal defects.

A 6-month-old male infant with partial atrioventricular canal defect and subaortic stenosis had a mitral valve releasing procedure to correct the subaortic stenosis with concomitant repair of the canal defect. An echocardiogram done 1 year after the operation shows no subaortic gradient and no mitral regurgitation. We present the details of the surgical technique and the common pitfalls in recognizing and treating this entity.

Aortic Valve Stenosis↗
PubMed1993

Paraspinal muscle evoked cerebral potentials in patients with unilateral low back pain.

Cerebral somatosensory evoked potentials (SEPs) were elicited by magnetic stimulation of paraspinal muscles unilaterally at the L2 and L5 levels in 20 healthy subjects and 16 patients with low back pain and unilateral muscle spasm. A magnetic coil with a mean diameter of 4.7 cm was placed tangentially to the skin. The stimulus strength was sufficient to induce a visible muscle twitch without producing muscle contraction in the legs. The potentials recorded over the scalp consisted of several components (P30, N40, P55, N70, and P90) and were elicited in all subjects. In both healthy and patient subjects, paraspinal muscle evoked potentials were readily elicited. Vibration applied to paraspinal muscles, as well as voluntary contraction of paraspinal muscles, was associated with attenuation of the evoked potentials. This finding suggests that muscle spindle receptors provide the afferent input responsible for the early components of the magnetically evoked cerebral potentials. In patients with unilateral muscle spasm, the amplitudes of P30-N40, N40-P50, and P50-N70 were decreased significantly on the affected side when compared with values on stimulation of the unaffected side, as well as those obtained from control subjects. The cerebral evoked potentials returned to normal amplitude when the muscle spasm subsided following a period of time and after the application of spinal manipulative therapy. The technique has potential for quantitative evaluation of muscle spasm in low back pain.

Adult↗