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Biomedical subjects

D M Green

Publications and source records attributed to D M Green.

At least 127 records · Page 7Linked to original sources
PubMed1993

Effects of treatment for childhood cancer on vital organ systems.

Advances in treatment have dramatically increased the survival rate of children and adolescents with cancer. These treatments, however, may be associated with damage to vital organ systems, which may not be evident until many years after the initial diagnosis of cancer and may adversely affect long-term survival and/or the quality of life of former patients. The effects of treatment on three specific organ systems, heart, lungs, and kidneys, are reviewed here.

Adolescent↗
PubMed1993

Epidemiology of Wilms tumor.

Wilms tumor affects approximately one child per 10,000 worldwide before the age of 15 years. Incidence rates appear to be slightly elevated for U.S. and African Blacks in comparison to Whites, but are only half as great among Asians. Several case-control studies have suggested that paternal occupational or maternal hormonal exposures during pregnancy may increase the risk of Wilms tumor, but small numbers of subjects and inconsistencies in the patterns of exposures do not permit firm conclusions to be drawn. It is unlikely that such environmental exposures play a major role in the etiology of Wilms tumor. The median age-at-onset of Wilms tumor is 38 months in the U.S. National Wilms Tumor Study series, with cases in girls occurring on average 6 months later than in boys. Patients with bilateral tumors, aniridia, cryptorchism/hypospadias, Beck-with-Wiedemann syndrome, or intralobar nephrogenic rests tend to be diagnosed much younger than average (median 17-27 months). Those with familial disease or multicentric tumors have intermediate age-at-onset distributions, while those with perilobar nephrogenic rests are diagnosed at older ages. The epidemiologic features suggest that somatic mosaicism, rather than a germline mutation, may be responsible for some of the bilateral and multicentric cases.

Africa↗
PubMed1993

Screening of children with hemihypertrophy, aniridia, and Beckwith-Wiedemann syndrome in patients with Wilms tumor: a report from the National Wilms Tumor Study.

To evaluate the usefulness of regular radiographic screening to detect an asymptomatic intraabdominal tumor in patients with an increased risk of developing Wilms tumor, we reviewed the files of patients with hemihypertrophy, aniridia, or Beckwith-Wiedemann syndrome who were registered on the National Wilms Tumor Studies. Screening was employed infrequently in the management of children with hemihypertrophy, with only 25% (6/24) of those whose hemihypertrophy was identified more than 30 days prior to the diagnosis of Wilms tumor undergoing such examinations. Most patients with aniridia were evaluated regularly for the occurrence of Wilms tumor. There were more stage 1 tumors identified in patients whose tumor was detected only through radiographic evaluation. The role of routine radiographic screening needs to be carefully evaluated in a homogeneous group of patients such as those with aniridia using a prospective study design to determine if such screening improves the survival rate of children with this rapidly growing, but readily treatable form of childhood cancer.

Adolescent↗
PubMed1993

Position paper: imaging methods for primary renal tumors of childhood: costs versus benefits.

The patterns of disease distribution at diagnosis and during follow-up were cataloged for the primary renal tumors of childhood. These data, derived from more than 1,500 patients, were used to define the most rewarding and cost-effective imaging methods required for patient management. The basic information needed prior to surgery includes whether there is a functioning kidney on the opposite side, and whether there are lung metastases or inferior vena cava thrombi. Simple X-ray examinations and ultrasonography (US) will provide the necessary data. Postoperatively, when the histology is known, examination of the brain (MRI or CT scan) is needed for patients with the rhabdoid tumor and clear cell sarcoma of the kidney (CCSK) who are prone to develop brain lesions; and the skeletal system (bone scan, X-ray skeletal survey) for CCSK and for renal cell carcinoma patients who tend to develop bone metastases. Continuing examination of the lung (chest films) is required for all histologies except perhaps for mesoblastic nephroma, which seldom metastasizes. The opposite kidney needs follow-up (US) for 5 or more years to exclude metachronous involvement if nephrogenic rests are present in either kidney. Sophisticated imaging studies, which cost five times or more than simple X-ray examinations or US, are not warranted routinely, and should be reserved for those cases where simpler, less expensive studies do not suffice for reaching patient management decisions.

Bone Neoplasms↗
PubMed1993

SIOP Working Committee on Psychosocial Issues in Pediatric Oncology.

Recognizing the importance of psychosocial issues in the care and cure of the child with cancer, the board of the International Society of Pediatric Oncology (SIOP) in 1991 constituted a Working Committee on Psychosocial Issues in Pediatric Oncology, with Giuseppe Masera as chair and John Spinetta as co-chair. This committee met for the first time in Rhodes, Greece, in October 1991. The committee discussed various psychosocial issues and developed a document on Aims and Recommendations, summarizing the experiences of major centers. This document was approved by the SIOP board, which recommended diffusion of the document to the pediatric oncology community.

Child↗
PubMed1993

Discrimination of spectral shape as a function of stimulus duration.

Thresholds for discriminating the changes in the spectral shape of simultaneously presented components (profile analysis) are measured as a function of stimulus duration for various complex stimuli. For all stimuli, the threshold decreases with increasing duration until a transition time is reached, and thereafter the threshold remains constant. The amount of change in threshold and the value of transition time appear to be greater for complexes having narrower frequency spacing of the components. The results can be accounted for, at least qualitatively, by assuming that the bandwidth of the auditory filters decreases after the onset of the stimulus.

Acoustic Stimulation↗
PubMed1993

Detecting temporal onset and offset asynchrony in multicomponent complexes.

The ability of listeners to detect asynchrony in either the temporal onset or offset of components in multicomponent complexes was measured. The listener discriminated a standard complex, one in which all components were synchronous, from an asynchronous complex. In the initial experiments, asynchrony was created by starting (onset experiments) or ending (offset experiments) the harmonics at times drawn from a Gaussian distribution. In later experiments, asynchrony was created by starting or terminating only certain components before or after the other components in the complex. One complex consisted of 20 harmonic components with a fundamental of 200 Hz. Another multicomponent complex used components spaced at equal intervals in logarithmic frequency (200 to 4000 Hz). The parameters investigated were rise or decay time of components, duration of a complex, and frequency position of displaced components. The obtained thresholds were different for onset and offset asynchrony. For onset asynchrony in harmonic complexes, the thresholds were a nonmonotonic function of rise time with a minimum of 0.2 ms obtained for a rise time of 1 ms. For offset asynchrony, thresholds were generally monotonic with increases in decay time and ranged from 0.45-1.3 ms. Experiments with a much shorter signal duration demonstrated that forward and backward masking played little role in the observed differences in thresholds. Onset thresholds for harmonic stimuli measured as a function of the frequency region of the asynchronous component(s) showed a minimum of 0.2 ms at about 2000 Hz. The thresholds for offset were about ten times larger. For logarithmic complexes, in some conditions, thresholds were larger by nearly two orders of magnitude. Experiments in which the listeners discriminated changes either in the onset or offset envelope of the wideband stimulus suggest that detection of temporal asynchrony depends on comparison between frequency channels rather than on differences in the temporal onset or offset of the overall energy of the sounds.

Acoustic Stimulation↗
PubMed1993

Auditory profile analysis of harmonic signals.

Spectral shape discrimination for harmonic complexes with 100-, 200-, or 400-Hz fundamental was investigated in two sets of experiments. In the first set, the signal was an increment in a single component of an otherwise equal-amplitude complex. The results of these experiments showed nearly a 30-dB increase in thresholds as the signal frequencies increased from 1000 to 5000 Hz. A transformation of data based on the assumption that the critical detection quantity is the change in the level in a critical band centered at the signal frequency was applied to remove the effects of the nonsignal components. The corrected thresholds have a bowl-like shape similar to that seen in studies of spectral shape discrimination of stimuli with components equally spaced on a logarithmic frequency scale. Additional experiments examined the effects of the number of components in the complex and the relative phase of the components of the harmonic complex. In the second set of experiments, the effects of local masking were examined either by increasing the level of several adjacent components, or by removing nonsignal components near a single signal component. Again, the results with harmonic signals are similar to those obtained with components spaced at equal intervals on a logarithmic frequency scale, if one calculates the increment in the level produced in a critical band centered at the signal frequency.

Acoustic Stimulation↗
PubMed1993

A maximum-likelihood method for estimating thresholds in a yes-no task.

A maximum-likelihood procedure for estimating threshold values in a yes-no task is presented. In computer simulations of this procedure, it is demonstrated that the variability of the threshold estimates is little affected by the density of the hypotheses tested for a fixed range, or by serious misestimates of the slope of the psychometric functions. The threshold value is also largely independent of the starting value of the signal. The standard deviation of the threshold estimates appears to decrease with the square root of the number of trials, with a 2- to 3-dB standard deviation possible if only 12 trials are used in the threshold estimates. Data are presented using human listeners tested on 5 days. Two threshold estimates, based on 12 trials, were made at each of the six audiometric frequencies on each day. The mean data appear sensible, and the standard deviation of the measured thresholds is about 3 dB. Using this procedure, it takes less than 3 min to measure the audiogram for a single ear.

Acoustic Stimulation↗
PubMed1993

Detecting temporal asynchrony with asynchronous standards.

The ability of listeners to detect asynchrony in either the temporal onset or offset of individual components in a multicomponent complex was investigated. A standard stimulus was created having a simple kind of asynchrony by linearly delaying successive components of a complex stimulus. Additional asynchrony (the signal) was created by altering the temporal position of a single component of the complex relative to its temporal position in the standard. Asynchrony discrimination was measured for harmonic signals (experiment I) and for complexes in which the components were logarithmically spaced in frequency (experiment II). For the onset condition, asynchrony in either the harmonic or logarithmic complex greatly increased the difficulty in detecting the temporal asynchrony of a single component. For the offset condition, asynchrony discrimination was not greatly affected by asynchrony in the standard.

Acoustic Stimulation↗
PubMed1993

Treatment outcomes in patients less than 2 years of age with small, stage I, favorable-histology Wilms' tumors: a report from the National Wilms' Tumor Study.

PURPOSE: Retrospective analyses were performed to determine the effect of tumor weight and therapy modifications on outcome in patients less than 2 years of age with stage I favorable-histology Wilms' tumors. PATIENTS AND METHODS: The 4-year relapse-free and overall survival percentages for patients randomized to different treatment regimens in National Wilms' Tumor Studies (NWTS)-1, -2, and -3 were calculated and compared. RESULTS: The 4-year relapse-free survival percentages of patients whose specimen weight was less than 550 g were found to be 89.1% on NWTS-1, 96.0% on NWTS-2, and 93.2% on NWTS-3. There was no evidence that the relapse-free survival of these patients had improved over time (P value for trend = .99). The 4-year relapse-free survival percentage for similar age and stage patients whose specimen weight was 550 g or greater was significantly poorer than that of patients with smaller tumors (P = .02). CONCLUSION: Changes in the NWTS treatment regimens over a period of more than 20 years have not improved on the excellent prognosis of patients who are less than 2 years of age at diagnosis and who have a stage I, favorable-histology Wilms' tumor with specimen weight less than 550 g. These data could be used as the basis for a future trial in which a subgroup of such patients is treated with nephrectomy only.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Diastolic hypertension in Wilms' tumor survivors: a late effect of treatment? A report from the National Wilms' Tumor Study Group.

Following treatment by the National Wilms' Tumor Study Group (NWTS) 2,243 children with Stages I-IV Wilms' tumor, have remained relapse-free for 5 or more years. Of these, 1,528 children had at least one blood pressure measurement recorded during follow-up. Using standards developed by the Second Task Force on Blood Pressure Control in Children, it appears that 5 or more years following diagnosis the general distribution of blood pressures for NWTS survivors may be above that for the national population, especially at the younger ages.

Adolescent↗
PubMed1992

The number of components in profile analysis tasks.

The central issue of this paper is how detection of a change in spectral shape depends on the number of components m that define the spectrum. First, a channel theory is reviewed and the predictions relating the detectability of such a change as a function of the number of components are derived. Second, the existing literature is reviewed. Most of it concerns the detection of an increment in a single tone of an m-component, equal-amplitude complex. The data are close (+/- 2 dB) to the predictions of the theory, which suggests that there is a relatively small change in threshold as the number of components increases. The consistency of the data is also discussed and hypotheses for discrepancies are presented. Finally, the results of an experiment measuring the detectability of a special spectral shape change is explored. In this case, all the changes are equal in size but some are opposite in sign, so that the summed change is zero. The results using this "balanced" spectral change are also consistent with the predictions of the theory and show that for this special kind of spectral change thresholds improve by nearly 7 dB as m increases from 4 to 24 components.

Adult↗