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Biomedical subjects

H J Simon

Publications and source records attributed to H J Simon.

At least 19 recordsLinked to original sources
PubMed1998

A vaccine consisting of recombinant Borrelia burgdorferi outer-surface protein A to prevent Lyme disease. Recombinant Outer-Surface Protein A Lyme Disease Vaccine Study Consortium.

BACKGROUND: Lyme disease is a multisystem inflammatory disease caused by infection with the tick-borne spirochete Borrelia burgdorferi and is the most common vector-borne infection in the United States. We assessed the efficacy of a recombinant vaccine consisting of outer-surface protein A (OspA) without adjuvant in subjects at risk for Lyme disease. METHODS: For this double-blind trial, 10,305 subjects 18 years of age or older were recruited at 14 sites in areas of the United States where Lyme disease was endemic; the subjects were randomly assigned to receive either placebo (5149 subjects) or 30 microg of OspA vaccine (5156 subjects). The first two injections were administered 1 month apart, and 7515 subjects also received a booster dose at 12 months. The subjects were observed for two seasons during which the risk of transmission of Lyme disease was high. The primary end point was the number of new clinically and serologically confirmed cases of Lyme disease. RESULTS: The efficacy of the vaccine was 68 percent in the first year of the study in the entire population and 92 percent in the second year among the 3745 subjects who received the third injection. The vaccine was well tolerated. There was a higher incidence of mild, self-limited local and systemic reactions in the vaccine group, but only during the seven days after vaccination. There was no significant increase in the frequency of arthritis or neurologic events in vaccine recipients. CONCLUSIONS: In this study, OspA vaccine was safe and effective in the prevention of Lyme disease.

Adolescent↗
PubMed1997

Perceived lateral position of narrow-band noise in hearing-impaired and normal-hearing listeners under conditions of equal sensation level and sound-pressure level.

The perceived lateral position of narrow-band noise (NBN) was studied in a graphic pointer task as a function of the method of compensation for interaural threshold asymmetries in hearing-impaired and normal-hearing subjects. The method of compensation consisted of equal sensation level (EqSL) or equal sound-pressure level (EqSPL) at the two ears within the same subject. The NBN signals were presented at 11 center frequencies with interaural intensity differences (IIDs) that varied from -20 to +20 dB. When equalizing by SL, the perceived lateral position is essentially linearly dependent on the degree and direction of asymmetry in asymmetric normal-hearing and hearing-impaired listeners. Equalizing by SPL shows no such dependency but produces images that are lateralized close to the midline. These results reveal that subjects may have adapted to their threshold asymmetries. These results will be discussed in terms of the fitting of binaural hearing aids.

Audiometry, Pure-Tone↗
PubMed1997

Closer to home (or home alone?) The British Columbia long-term care system in transition.

Finding ways to organize and deliver long-term care that provides for quality of life at an affordable price is of increasing importance as the population ages, family size decreases, and women enter the workforce. For the past 2 decades, British Columbia has provided a model system that has apparently avoided disruptive conflicts. Although formal users' complaints are rare, this study--based on focus groups and interviews with users, their families, and advocates--identified problems users encountered toward resolving concerns about the structure, process, and outcome of long-term care. We present these findings in the context of British Columbia's current devolution from provincial to regional control that aims to save costs and keep disabled elderly persons in the community. British Columbia may be continuing to lead the way in meeting the needs of its burgeoning elderly population for long-term care. Study findings have implications for the development of US long-term care policy by pointing to the value of obtaining users' views of long-term care to identify both obvious and more subtle trouble spots.

Aged↗
PubMed1994

The measurement of the lateralization of narrow bands of noise using an acoustic pointing paradigm: the effect of sound-pressure level.

The effects of varying interaural time delay (ITD) and interaural intensity difference (IID) were measured in normal-hearing subjects as a function of eleven frequencies and at sound-pressure levels (SPL) from 60 to 90 dB SPL and at 25-dB sensation level. Using an "acoustic" pointing paradigm, the IID of a 500-Hz narrow-band (100 Hz) noise (the "pointer") was varied by the subject to coincide with that of a "target" ITD stimulus. ITDs of 0, +/- 200, and +/- 400 microseconds were obtained through total waveform delays of narrow-band noise (NBN), including envelope and fine structure. The results of this experiment confirm the traditional view of binaural hearing for like stimuli: There is little perceived displacement away from 0 IID at frequencies of 1250 Hz and above. In the low frequencies, subjects required IIDs greater than the expected 10 dB to perceive a fully lateralized image, and they varied in the maximum value of IID that they required, regardless of frequency. Our subjects did not always perceive the intracranial locations of ITD targets symmetrically: When the signal was delayed to one ear, the resultant matching IID was often different in magnitude than for the same ITD target delayed to the opposite ear for the identical frequency. The results of two subjects suggested that people with asymmetric normal hearing have adapted to their asymmetry for lateralization tasks: The subjects were found to lateralize toward the ear with the greater SPL stimulus, regardless of the ear to which the signal was delayed, when signals of equal SL were presented, and toward the leading ear when signals of equal SPL were presented (unequal SL). Increasing the presentation levels above 60 dB SPL had an effect on the perception of high-frequency ITD targets: As the intensity level increased, the slopes of the IID versus ITD functions increased indicating better discrimination of ITD. This study is in agreement with other studies in providing strong evidence of individual differences in lateralization experiments. These individual differences might be attributable to differential sensitivity to ambiguous time stimulus cues, differential task sensitivity, age effects, threshold asymmetries, or criterion variability.

Adult↗
PubMed1993

Optical third harmonic generation study of the hydration of DNA films.

Optical third harmonic generation (THG) has been observed for the first time from DNA films. The THG signal is observed from NaDNA films exposed to relative humidities (RHs) between 0% and 98%. A strong enhancement (approximately 5x) of the THG signal from NaDNA is observed at 84% RH; no enhancement is observed for RbDNA. The most likely mechanism for such an enhancement is an increased coherence length. A model calculation using estimates of the refractive indices at both the fundamental and third harmonic frequencies supports this interpretation. The observed THG signal has the same polarization as the incident (fundamental) light. For the A conformation, the THG signal polarized perpendicular to the helical axis is approximately twice as strong as the signal polarized parallel to the helical axis. No such anisotropy is observed for either the disordered conformation (below about 50% RH) or the B conformation (above 92% RH).

Biophysics↗
PubMed1993

Frequency discrimination in listeners with sensorineural hearing loss.

The difference limen for frequency (DLF) was measured in both ears of 34 hearing-impaired subjects at the octave and interoctave frequencies between 500 and 4000 Hz. In agreement with previous studies of DLF in the hearing impaired, there was only a moderate correlation (0.49) between DLF/F and hearing threshold level (HTL). Correlation and regression analyses at the individual frequencies, however, indicated that DLF/F is much more closely related to HTL at 1000 Hz and above than it is below 1000 Hz. Comparison of the right-left ear differences in DLF and HTL revealed some large DLF differences where there was no HTL difference and some large HTL differences where no DLF difference was found. The lack of a strong relationship between DLF and HTL asymmetries indicates that the structures that limit the DLF and the HTL may, at the same frequency, be damaged differently in each ear of the same subject.

Acoustic Stimulation↗
PubMed1992

Acute traumatic aortic rupture: intravascular US findings.

Traumatic aortic rupture is a lethal injury that requires immediate diagnosis and surgical repair. The authors report a case of acute aortic rupture in which aortography demonstrated a subtle intimal discontinuity at the cephalic margin of the aortic spindle. Intravascular ultrasound (US) imaging of the aorta demonstrated a mural flap and a small, contained hematoma. Intravascular US may have a role in enabling confirmation or clarification of subtle aortic abnormalities.

Adult↗
PubMed1989

[Reduced myocardial fatty acid utilization in coronary heart disease following symptom limited ergometric stress. Detection of pathologic metabolic patterns using iodine-123-phenylpentadecanoic acid and sequential SPECT].

Regional cardiac free fatty acid metabolism of 41 patients with coronary artery disease (CAD) and of 10 controls with normal coronary arteries was studied by means of I-123 phenylpentadecanoic acid (IPPA), a radioiodinated palmitic acid analog, and sequential single photon emission tomography (SPECT). All patients and controls underwent symptom--limited bicycle exercise, with the tracer being injected at peak stress. More than 99% of left ventricular segment of controls showed homogeneous tracer uptake and release, indicating homogeneous free fatty acid turnover in normal myocardium. Homogeneous postexercise uptake was followed by decreasing segmental activity in 75.1% of normally perfused segments in patients with CAD. Sixty-five percent and 88.6% of segments, assigned to the perfusion bed of 50%-75% and greater than 75% obstructed vessels had decreased IPPA release and/or reduced IPPA uptake. Patients with exercise induced ischemia had focal metabolic abnormalities in jeopardized myocardium for significantly longer time than clinical or electrocardiographic signs of ischemia (p less than 0.01). All patients with CAD and a negative stress test had metabolic abnormalities, but exhibited, compared to ECG--positive patients, less pronounced segmental metabolic aberrations. These findings indicate reduced cardiac utilization and delayed oxidation of IPPA, associated with exercise-induced ischemia in CAD. The metabolic changes suggest a marked sensitivity to ischemia as well as prolonged postischemic abnormalities of cardiac fatty acid metabolism in jeopardized myocardium.

Angina Pectoris↗
PubMed1987

Private financing options for long-term care.

Private financing for long-term care now comes almost exclusively from out-of-pocket payments. Long-term-care costs quickly impoverish most elderly, resulting in Medicaid dependency. The consequences are profound for the western Sun Belt with its rapidly growing elderly population. Key private financing options are long-term-care individual retirement accounts (LTC/IRAs), home equity conversion, social-health maintenance organizations and long-term-care insurance. Study of data from the past half century suggests that the LTC/IRA approach would prove unsatisfactory for the purpose despite the intuitive appeal of this mechanism. Experience with home equity conversions is still very limited, and unresolved questions limit this approach to the role of a reserve option for now. While promising, social-health maintenance organizations are still in the experimental stages and not yet commercially available. Long-term-care insurance is currently sold on a thin market and emphasizes nursing home coverage. New approaches to private financing through long-term-care insurance seem to offer the best approach for immediate implementation.

Aged↗
PubMed1987

Quantitative evaluation of myocardial stress/rest 201TL SPECT: results of a ROI-based method in 108 patients with CHD.

ROI-based polar maps (33 ROIs) were employed to evaluate quantitatively stress/rest myocardial 201Tl SPECT in 108 patients with angiographically proven coronary heart disease (CHD) in comparison with 30 controls. Sensitivity in detecting a CHD with stenoses of greater than 50% of luminal diameter was determined versus normal regional values (+/- 2.5 SD) employing vitality (VI) and wash-out corrected redistribution (RD). The method was evaluated referring to the severity of the disease, to the number of ROIs displaying changes [(a) 1 ROI, (b) greater than 2 ROIs], to validity of VI, RD or a combination thereof, and for specificity. Wash-out values were found to depend on degree of stress individually achieved and thus were not used as a threshold criterion. Sensitivity in supply areas with old myocardial infarctions was 95% (a) and 86% (b), resp. With no infarction, it was 96% (a) and 79% (b), resp. VI in stenosis greater than 75% was more sensitive than RD. However, combined evaluation of VI and RD yielded sensitivities from 91-100% (a) and 77-94% (b), resp. for different main supply areas. In stenosis less than 50% with normal VI, RD was positive in 18-31%. Specificity turned out to be 91% (a) and 97% (b), resp. We conclude that the method presented is reliable to quantify numerically 201Tl kinetics in myocardial SPECT, aimed at detecting and describing CHD.

Adult↗
PubMed1987

Speech discrimination with an 8-channel compression hearing aid and conventional aids in background of speech-band noise.

The design for a multichannel compression hearing aid was developed from previous experimental and theoretical work in our laboratory concerning pitch perception in normal-hearing subjects. The new hearing aid, implemented with off-line digital signal processing, was tested on twenty subjects with sensorineural hearing loss using speech sounds in a background of speech-spectrum noise. Five signal-to-noise ratios (+15 to -5dB) were used at two noise levels (60 and 70 dB SPL). Hearing-loss subjects listened to these stimuli under three different conditions: a) processed by the new multichannel compression hearing aid; b) processed by a conventional hearing aid; and c) unprocessed. The performance of normal-hearing subjects with the unprocessed stimuli provided another condition against which the performance in the two hearing aid conditions could be evaluated. Both aided conditions provided improved performance over the unprocessed condition and the multichannel compression aid produced better performance than the conventional aid. In the case of 4 of the 20 subjects, with less severe gradually sloping hearing losses, the new multichannel compression aid produced near-normal performance even at low signal-to-noise ratios. Some aspects of the results also suggested that learning to use the aid was more important in the case of the multichannel compression aid than in the case of the conventional aid. These results indicate that a multichannel compression hearing aid can be very effective in some individuals with sensorineural hearing loss and is superior to a conventional hearing aid in most subjects.

Acoustics↗
PubMed1987

[Effect of various liver diseases on the activity of 2 subtypes of cytochrome P-450].

The elimination of caffeine from the plasma and the elimination of metamizol-metabolites in urine were determined in 37 patients with different liver diseases. In severe liver diseases the demethylation of caffeine as well as the metabolism of metamizol is significantly reduced. The extent of reduced elimination capacity depends on the severity of the disease rather than on the type of disease. In patients with liver cirrhosis the determination of synthesis capacity and of humoral activity (s. tab. I) is suitable to evaluate the capacity of the cytochrome P-450 system. In noncirrhotic diseases only the activity of liver disease (tab. I.) determines the extent of reduced biotransformation capacity. Beside biotransformation-phase I, the acetylation--phase II biotransformation--also appears to be reduced.

Adult↗
PubMed1986

Affirmative action at work: a survey of graduates of the University of California, San Diego, Medical School.

Reported here are the results of a mail survey of 113 graduates from the University of California, San Diego, School of Medicine. Fifty-seven had been admitted with assistance of the Special Admissions Subcommittee (SAS) and 56 had been admitted through the traditional Recruitment and Admissions Committee mechanisms. SAS graduates see more patients daily, and practice more often in primary care specialties in rural and inner-city areas, providing medical care for ethnic minorities from lower socioeconomic strata.

California↗