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S Hellman

Publications and source records attributed to S Hellman.

At least 55 records · Page 3Linked to original sources
PubMed1995

Preferred listening levels for linear and slow-acting compression hearing aids.

OBJECTIVE: The purpose of the present experiment was to determine the relationship between most comfortable listening level and preferred listening levels for linear and slow-acting compression hearing aids as a function of variations in speech and noise level. DESIGN: A digital hearing aid test system was used to simulate six hearing aids having compression ratios of 1, 1.5, 2, 3, 5, and 10:1. Speech was presented in three different noises (vent, apartment, and cafeteria), with speech input level being varied (55, 70, 85 dB SPL). Subjects were 20 listeners with sensorineural hearing loss (half with a dynamic range < or = 30 dB and half with a dynamic range >30 dB). The boundaries of the most comfortable listening range were measured to estimate most comfortable listening level. Preferred listening level was measured by having subjects adjust the output of the hearing aid for satisfactory listening. RESULTS: On average, the deviation of preferred listening level from most comfortable loudness (MCL) was less than 5 dB. Dynamic range, noise type, and input level were all found to have small, but significant, effects on the deviation of preferred listening level from MCL. On average, subjects with a small dynamic range listened slightly below MCL, and subjects with a larger dynamic range listened slightly above MCL. For favorable signal-to-noise ratios, preferred listening levels were highest for high input levels and for conditions that resulted in high output levels before level adjustment. Although the pattern of average performance differed slightly at poorer signal-to-noise ratios, all preferred listening levels were close to MCL. CONCLUSIONS: The gain of a slow-acting compression hearing aid should place the output within 5 dB of MCL. The output for low and medium inputs should approximate MCL and the output for high input levels should be slightly above MCL. This pattern of gain may be obtained with mild compression ratios and a gain rule that places a speech input of 70 dB at MCL.

Audiometry, Pure-Tone↗
PubMed1995

Methylmethacrylate monomer produces direct relaxation of vascular smooth muscle in vitro.

Methylmethacrylate bone cement is associated with severe hypotensive reactions during surgery and anesthesia. The purpose of this in vitro study was to determine if methylmethacrylate monomer could produce hypotension by acting directly on vascular smooth muscle. Segments of human saphenous vein or rabbit thoracic aorta were cut into rings. The rings were mounted in isolated tissue chambers in order to measure isometric tension development. Methylmethacrylate monomer (methylmethacrylic acid ester) produced direct relaxation of venous or aortic rings preconstricted with either potassium ion or noradrenaline. The relaxation was concentration-dependent, occurring at concentrations from 10(-3) to 10(-1) M. The relaxation of rabbit aortic rings (preconstricted with noradrenaline) was unaffected by pre-treatment with atropine, propranolol, cimetidine, indomethacin, or methylene blue. Endothelial stripping with Triton X-100, sufficient to completely abolish acetylcholine-induced relaxation, also had little effect on methylmethacrylate-induced relaxation. Methylmethacrylate produced direct relaxation of rabbit aortic rings constricted with either potassium or noradrenaline in calcium-deficient media, and inhibited subsequent calcium-induced constriction. These results suggest that methylmethacrylate monomer may interfere with intracellular and extracellular calcium mobilization and excitation/contraction coupling in vascular smooth muscle. The direct relaxation of venous and arterial smooth muscle produced by methylmethacrylate monomer may contribute in part to the hypotension that can occur when acrylic bone cement is employed during orthopedic procedures.

Animals↗
PubMed1995

Effect of release time in compression hearing aids: paired-comparison judgments of quality.

Paired-comparison judgments of quality were obtained from 20 hearing-impaired listeners for speech processed through simulated compression hearing aids varying in release time (60, 200, 1000 ms) at three different compression ratios (1.5, 2, 3:1) and for three different background noises (ventilation, apartment, cafeteria). Analysis revealed that the main effect of release time did not have a significant effect on perceived quality. The interaction between release time and noise type was found to be significant. While no significant difference in preference for release times was evident for the ventilation noise, the longer release times (200 and 1000 ms) were preferred for the higher level noises (apartment noise, cafeteria noise). Post hoc testing revealed that the mean preference scores for the 200- and 1000-ms release time were significantly greater than that of the 60-ms release time with the competing cafeteria noise (p < 0.05). Analysis of individual subject data revealed statistically significant preferences that differed from the group mean, suggesting that individualized fitting of this parameter of a compression hearing aid might be warranted.

Adolescent↗
PubMed1995

Oligometastases.

Explore the source record for details and available documents.

Humans↗
PubMed1995

Natural history of node-negative breast cancer: a study of 826 patients with long-term follow-up.

PURPOSE: We were interested in examining the long-term outcome of patients with node-negative breast cancer to address the following questions: (1) Is node-negative breast cancer a disease that is curable by local modalities? (2) Are there predictors of disseminated disease in node-negative breast cancer? (3) Are there subgroups of tumors that have different times to recurrence? METHODS: From 1927 to 1984, 826 women with node-negative breast cancer were treated at the University of Chicago. Patients underwent either a radical or extended radical mastectomy (83%) or a modified radical mastectomy (13%). RESULTS: Follow-up evaluation ranged from 9 to 523 months (43.6 years); the mean follow-up period of survivors is 162 months (13.5 years). On multivariate analysis, the strongest predictor of outcome and time to relapse was pathologic tumor size. Patients with tumors less than 2 cm had a 20-year disease-free survival (DFS) rate of 79% and a median time to recurrence of 48 months as compared with patients with tumors greater than 2 cm, who had a survival rate of 64% (P < .001) and a median time to recurrence of 37 months (P = .01). CONCLUSION: With extended follow-up evaluation, node-negative breast cancer is a curable disease. Size is the strongest predictor of dissemination and rate of relapse. These data suggest that given the natural history of node-negative breast cancer, analysis of clinical trials with short follow-up periods can be misleading, since it may identify those patients whose tumors have a greater virulence but not necessarily a greater likelihood to metastasize.

Actuarial Analysis↗
PubMed1994

Radiation oncology.

Radiosurgery has been effective in the treatment of otherwise inaccessible arteriovenous malformations. Perhaps the most exciting developments in dose optimization are in conformal radiation therapy. The use of radiation therapy and concomitant chemotherapy has been shown to improve survival in some patients with carcinoma of the anus, rectum, and head and neck.

Humans↗
PubMed1994

Effect of compression ratio in a slow-acting compression hearing aid: paired-comparison judgments of quality.

Paired-comparison judgments of quality were obtained from 20 hearing-impaired listeners (half with a small dynamic range and half with a large dynamic range) for speech-in-noise (vent, apartment, and cafeteria) processed through a slow-acting compression hearing aid. Compression ratio was varied (1, 1.5, 2, 3, 5, and 10:1). Compression threshold, attack time, and release time were fixed. Sound quality judgments were significantly affected by compression ratio, noise, and dynamic range. Preference decreased with increasing compression ratio. The selection of compression ratio. The selection of compression ratios < or = 2:1 was significantly higher than of compression ratios > 3:1. Less compression (no compression or 1.5:1) was preferred with the highest level noise (cafeteria noise) than with the lower level noises (vent or apartment). In particular, the small dynamic range group preferred compression with the vent and apartment noises (noise below the compression threshold), but preferred a linear hearing aid with the cafeteria noise (above the compression threshold). The large dynamic range group showed a slightly greater preference for the linear hearing aid for all three noises.

Adolescent↗
PubMed1993

Dogma and inquisition in medicine. Breast cancer as a case study.

This case study demonstrates the similarity between the development of dogma and the persecution of deviants during the Spanish Inquisition and that in medicine using breast cancer as an example. Regarding breast cancer, the dogma of therapy became separate from the underlying hypothesis and, like the religious dogma enforced by the Inquisition, it required inflexible adherence. Apostates were publicly chastened. This serves to inhibit debate and the exploration of alternative hypotheses, both of which are essential for the advancement of scientific knowledge. Adherance to dogma is antithetical to the conditional and approximate nature of truth in science.

Attitude of Health Personnel↗
PubMed1993

Patterns of presentation of Hodgkin disease. Implications for etiology and pathogenesis.

BACKGROUND: The etiology of Hodgkin disease remains uncertain. Patterns of presentation of Hodgkin disease are analyzed by histologic subtype with implications for etiology and pathogenesis. METHODS: The authors performed a detailed analysis of anatomic sites of involvement, histopathologic findings, and clinical features in 719 patients with Hodgkin disease who underwent staging laparotomy with splenectomy between April 1969 and December 1986. The presence of disease in each of 17 sites of potential nodal involvement was determined for each patient from a combination of clinical and surgical staging. Association among nodal sites was assessed in 2 x 2 tables by estimating the odds ratio and testing the significance with the chi-square test. A strict significance level (P = 0.01) was used. Log-linear models were used for assessing association in 2 x 2 tables while adjusting for other factors. RESULTS: The mediastinum, left side of neck, and right side of neck were the most common sites involved for patients with nodular sclerosing (NS) or mixed cellularity (MC) histologic subtypes. Each of these sites was involved 60% of the time. These sites were four or more times as common as other nodal sites above or below the diaphragm. In contrast, the mediastinum was involved in only 8% of patients with lymphocyte predominance (LP) histologic subtype. Significant associations were found between mediastinal disease and low cervical/supraclavicular lymph node disease, mediastinal disease and NS histologic subtypes, peripheral nodal disease and LP histologic subtypes, and between splenic disease and mixed cellularity/lymphocyte depletion (MC/LD) Hodgkin disease. The age at onset and sex of patients with Hodgkin disease and the patterns of nodal distribution were somewhat different for NS and MC/LD histologic subtypes. Even greater differences were seen between LP and other histologic subtypes. CONCLUSIONS: This study supports the conclusion that NS and MC Hodgkin disease spread by continguity, most often originating in the neck or mediastinum, and is consistent with evidence suggesting an infectious agent in the pathogenesis of these subtypes of Hodgkin disease. In contrast, LP Hodgkin disease is characterized by different sites of presentation and patterns of spread. This suggests that two or perhaps three clinicopathologic subtypes of Hodgkin disease exist. Implications for etiology and pathogenesis are discussed.

Adult↗
PubMed1993

Episodic coma due to acute basilar artery migraine: correlation of EEG and brainstem auditory evoked potential patterns.

Our patient presented with three episodes of deep coma in 5 weeks, followed by a complete recovery. The neuroradiological tests and spinal fluid analysis excluded structural lesions, including subarachnoid hemorrhage, from the diagnosis. A nonconvulsive status was excluded by 24-hour EEG monitoring. The EEGs and brainstem auditory evoked responses were abnormal during ictus, but they reversed to normal with the clinical recovery. Timely neurophysiological tests helped in the diagnosis of basilar artery migraine.

Basilar Artery↗
PubMed1993

Hematopoietic stem cell deficit of transplanted bone marrow previously exposed to cytotoxic agents.

High-dose chemotherapy and/or total body irradiation followed by autologous bone marrow rescue has improved the survival of patients with a variety of malignancies. Candidates for autologous bone marrow transplantation (ABMT) often have received prior exposure to cytotoxic agents, some of which may damage primitive stem cells. We have developed an in vivo murine model to evaluate the effects of a number of individual cytotoxic agents on the ability of syngeneic donor marrow to provide long-term hematopoiesis in recipients following high-dose total body irradiation. Marrow was experimentally obtained by giving donor mice 6 weekly injections of saline, cytosine arabinoside, cyclophosphamide, cisplatin, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), or busulfan, drugs known to have differing effects on primitive hematopoietic stem cells. After time to allow recovery of marrow and peripheral blood counts, 1 x 10(7) marrow cells from these mice were transplanted into lethally irradiated syngeneic recipients. Five to 6 months after marrow transplantation, the quality of long-term hematopoietic recovery was measured by WBC counts, marrow cellularity, CFU-S content, and determinations of stem cell self-renewal. Abnormalities were noted with the use of donor marrow exposed to all cytotoxic agents. Recipients of marrow previously exposed to cytosine arabinoside, an agent that spares the most primitive stem cells, were the least affected. Recipients of marrow previously exposed to busulfan, an agent known to damage primitive stem cells, were most affected with a decrease in peripheral blood counts, marrow cellularity, stem cell content, self-renewal capacity, and long-term survival. A decrease in hematopoietic stem cell self-renewal was seen in recipients of marrow previously exposed to cyclophosphamide, cisplatin, and BCNU even when marrow cellularity and CFU-S content were normal. These data suggest that the capacity of syngeneic donor marrow to provide long-term hematopoiesis in lethally irradiated recipients is dependent on its donor marrow primitive stem cell content. Long-term hematopoiesis may be severely compromised in recipients of donor stem cells previously exposed to cytotoxic agents which damage primitive stem cells.

Animals↗
PubMed1992

Effects of noise and noise suppression on speech perception by cochlear implant users.

The recognition of phonemes in consonant-vowel-consonant words, presented in speech-shaped random noise, was measured as a function of signal to noise ratio (S/N) in 10 normally hearing adults and 10 successful adult users of the Nucleus cochlear implant. Optimal scores (measured at a S/N of +25 dB) were 98% for the average normal subject and 42% for the average implantee. Phoneme recognition threshold was defined as the S/N at which the phoneme recognition score fell to 50% of its optimal value. This threshold was -2 dB for the average normal subject and +9 dB for the average implantee. Application of a digital noise suppression algorithm (INTEL) to the mixed speech plus noise signal had no effect on the optimal phoneme recognition score of either group or on the phoneme recognition threshold of the normal group. It did, however, improve the phoneme recognition threshold of the implant group by an average of 4 to 5 dB. These findings illustrate the noise susceptibility of Nucleus cochlear implant users and suggest that single-channel digital noise reduction techniques may offer some relief from this problem.

Adult↗