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Biomedical subjects

R G Schwartz

Publications and source records attributed to R G Schwartz.

At least 19 recordsLinked to original sources
PubMed1995

Effect of familiarity on word duration in children's speech: a preliminary investigation.

Young children's productions of novel words were used to investigate the influence of word familiarity on vowel and word duration. Ten children, 18 to 21 months old, produced tokens of phonologically individualized words (from one to four words) over 12 experimental sessions. Comparisons of means for the individualized words revealed that productions in the second half of the sessions were significantly shorter (both in their vowel and overall duration) than those in the first six sessions. When mean durations of productions were derived for each child, the effect held for word durations. Vowel durations differed in the same direction, but the difference was not statistically significant. Under these controlled conditions, familiarity seemed to influence the duration of early productions of novel words. These findings are discussed as evidence of word-specific motor maturation in early lexical acquisition.

Age Factors↗
PubMed1995

Metrical patterns of words and production accuracy.

This investigation examined the influence of metrical patterns of words (syllable stress and serial position) on the production accuracy of 20 children (22 to 28 months). The data were productions of six pairs of individualized two-syllable experimental words that referred to unfamiliar objects. Members of each pair differed only in the placement of stress (e.g., ['soti] vs. [so'ti]). Unstressed syllables were much more likely to be omitted, particularly at the beginning of words. Very few stressed syllables and unstressed second position syllables were omitted. One fourth of the word initial unstressed syllables were omitted. Consonant omissions, though few in number, tended to occur in initial position. Assimilation errors were not influenced by stress or serial position. When segmental errors due to syllable omissions were excluded, other consonant errors were not affected by stress or serial position. These findings indicate that young children's productions of syllables are influenced by the metrical patterns of words. However, the trochaic pattern of English is a statistical tendency, not an absolute constraint on two-syllable words. Metrical pattern also does not affect the consonant accuracy in syllables produced.

Child Language↗
PubMed1992

Converging evidence for underlying phonological representation in a child who misarticulates.

The liquid, fricative, and affricate sounds in the phonological system of a single misarticulating child were the focus of converging analyses. These analyses included structured measures of perceptual and productive skills, language sampling, and acoustic analysis of seemingly homophonous forms. The results of perceptual and productive tasks indicated that the child's perception of certain sounds was superior to his productions, but for other sounds, productive skill was superior to perceptual performance. This child's errors of production could be attributed to nonadultlike underlying representations. A two-lexicon model of underlying representation best accounted for the data. The findings led to inferences about the child's underlying perceptual and articulatory knowledge of fricative, affricate, and liquid sounds.

Articulation Disorders↗
PubMed1992

Leucine as a regulator of whole body and skeletal muscle protein metabolism in humans.

Leucine has been proposed as an in vivo regulator of protein metabolism, although the evidence for this in humans remains inconclusive. To test this hypothesis, we infused either L-leucine (154 +/- 1 mumol.kg-1 x h-1) or saline intravenously in six healthy men in two separate studies. L-Leucine infusion increased plasma concentrations of leucine and alpha-ketoisocaproate from 112 +/- 6 and 38 +/- 3 mumol/l to 480 +/- 27 (P < 0.001) and 94 +/- 13 mumol/l (P < 0.001), respectively, without any significant change in circulating insulin or C peptide levels. Leucine infusion decreased plasma concentrations of several amino acids and decreased whole body valine flux and valine oxidation (using L-[1-13C]valine as a tracer) and phenylalanine flux (using [2H5]-phenylalanine as a tracer). According to arteriovenous differences across the leg, the net balance of phenylalanine, valine, and lysine shifted toward greater retention during leucine infusion, whereas alanine balance did not change. Valine release and phenylalanine release from the leg (estimated from the dilution of respective tracers) decreased, indicating inhibition of protein degradation by leucine infusion. We conclude that leucine decreases protein degradation in humans and that this decreased protein degradation during leucine infusion contributes to the decrease in plasma essential amino acids. This study suggests a potential role for leucine as a regulator of protein metabolism in humans.

Adult↗
PubMed1992

Cumulative trauma disorders.

Cumulative trauma disorders have increased five-fold since 1979 and now account for up to 47% of workplace injuries. Nerve entrapment, tendonitis, and other soft tissue injuries are the most common diagnostic groups. Both occupational and non-occupational factors contribute to the etiology of these disorders. Epidemiology, differential diagnosis, and interventions for treatment are reviewed.

Cumulative Trauma Disorders↗
PubMed1992

Guidelines for cardiac monitoring of children during and after anthracycline therapy: report of the Cardiology Committee of the Childrens Cancer Study Group.

The anthracycline antibiotics, daunorubicin, doxorubicin, and the newer derivatives, are important components of many antineoplastic chemotherapeutic regimens. Their usefulness is limited by their cardiotoxicity. Sequential monitoring of cardiac function of patients undergoing chemotherapy allows identification of subclinical cardiotoxicity. In many patients monitoring can thus guide the modification of the chemotherapy to minimize cumulative cardiotoxicity, reducing acute and long-term clinical and subclinical sequelae. Such monitoring also aids in the comparison of cardiotoxicity produced by different drugs and different methods and schedules of drug administration. The considerable variability of monitoring regimens between institutions and in the literature has detracted from its usefulness. The Cardiology Committee of the Childrens Cancer Study Group has, therefore, reviewed the field and has formulated recommendations for standardized noninvasive monitoring of children during and immediately after chemotherapy and for the modification of the chemotherapy where indicated.

Antibiotics, Antineoplastic↗
PubMed1991

Reduced metabolic rate during beta-adrenergic blockade in humans.

We previously reported that 1 week of propranolol treatment (160 to 240 mg/d, orally) reduced resting metabolic rate (RMR) an average of 9% in healthy men. To determine whether this response was caused by the 25% reduction in serum triidothyronine (T3), rather than beta-adrenergic blockade, we examined the effect of nadolol on RMR in five healthy men. Nadolol is a nonselective beta-adrenergic antagonist that does not affect T3 production. After 6 to 10 days of nadolol treatment (240 mg/d), mean postabsorptive RMR declined 7% (P less than .01), with no significant change in serum T3 or thyroxine (T4) concentrations. This effect is significantly different from that of a hospitalized control group that received no drug and had no change in mean RMR, and was not different from the response to propranolol (previously published data). Nadolol slightly reduced the mean thermic response to a meal (12%), but this effect was not statistically significant. Mean postprandial RMR was 8% lower after nadolol treatment (P less than .01), mainly because of the reduced postabsorptive RMR, rather than a change in the response to the meal. These data suggest that beta-adrenergic activity makes a small but significant contribution to resting energy expenditure in man.

Adult↗
PubMed1990

Radiation effects on left ventricular function and myocardial perfusion in long term survivors of Hodgkin's disease.

We evaluated systolic and diastolic indices of left ventricular performance by radionuclide angiocardiography and myocardial perfusion with exercise/rest thallium scintigraphy in 16 patients previously irradiated for Hodgkin's disease. These commonly used indices of left ventricular (LV) performance included LV ejection fraction (LVEF) as a measure of systolic function, and LV peak filling rate (PFR) as a measure of diastolic function. The presence of coronary artery disease (CAD) was evaluated by ECG treadmill testing (13 patients) and by quantitative planar thallium scintigraphy (12 patients). Patients were 16-38 years old (mean 24.9 +/- SD 6.2) at the tim eof irradiation, and were evaluated 2.5-21.5 years (mean 9.3 +/- 6.3) after radiation therapy (RT). RT was delivered with beam energies of 2-18 MV, equally weighted AP-PA mantle fields with both fields treated daily for most patients (13 patients), and fraction sizes of 1.5-2.0 Gy. Six patients received radiation to th entire cardiac volume, most commonly via left-sided partial transmission lung blocks (PTLB). Patient data were analyzed according to the volume of heart treated. Individuals who had the entire cardiac volume irradiated were assigned to group I (N = 6), and those patients who had some portion of the heart shielded throughout treatment comprised group II (N = 10). In this series, no perfusion defects were evident in either group by quantitative planar thallium scintigraphy. Mean LVEF for all patients studied was 60% (normal LVEF greater than or equal to 50%). Patients in group I had a lower mean LVEF than those in group II, 55 +/- 4% versus 63 +/- 6% (p = 0.01). Mean PFR for all patients studied was normal at 3.5 EDV/sec (normal PFR greater than or equal to 2.54 EDV/sec). Patients in group I had a lower mean PFR than those in group II, 3.0 +/- 0.6 vs 3.8 +/- 0.7 EDV/sec (p = 0.04). Thus, patients irradiated to large cardiac and pulmonary volumes had lower LVEF and PFR within the normal range compared to patients who had some portion of the cardiac volume shielded. These differences are statistically significant in the relatively small groups studied but do not appear to be associated at the present time with clinically significant effects.

Adolescent↗
PubMed1989

Cost-benefit analysis of early return to work after uncomplicated acute myocardial infarction.

The economic consequences of an Occupational Work Evaluation designed to identify low risk patients recovering from uncomplicated acute myocardial infarction (AMI) and hasten their return to work was evaluated in a randomized trial. Two hundred one employed, clinically low risk men recovering from AMI were randomized to undergo an intervention (intervention group, 99 patients) consisting of an Occupational Work Evaluation or to receive usual care (usual care group, 102 patients). The time to return to work was reduced from 75 days in usual care patients to 51 days in intervention patients (p less than 0.002). Significant differences were found between groups for medical costs and occupational income during follow-up. Total medical costs per patient were lower in the intervention patients than in the usual care patients in the 6 months after AMI ($2,970 vs $3,472). Occupational income per patient was higher in intervention patients than in the usual care group in the 6 months after AMI ($9,655 vs $7,553). The per capita benefit accounting for medical costs and occupational income was $6,685 for intervention patients and $4,081 for usual care patients. Projected to the greater than 300,000 low risk, employed survivors of AMI annually in this country, the savings generated by the Occupational Work Evaluation could yield an annual economic benefit greater than 800 million dollars.

Algorithms↗
PubMed1989

Superiority of visual versus computerized echocardiographic estimation of radionuclide left ventricular ejection fraction.

An optimal method for determining left ventricular ejection fraction (LVEF) by echocardiography should be rapid, reliable, and widely applicable in order to be utilized routinely in a busy clinical laboratory. Most methods reported in the literature are reliable in selected, high-quality echocardiograms. Most require off-line computer analysis and are time-consuming and poorly suited to the routine of a busy laboratory. We compared in a blinded manner several echocardiographic methods of LVEF determination with the ejection fraction obtained by equilibrium radionuclide angiography (ERNA) in 44 patients unselected for image quality. Echocardiographic methods included: [1] cubed M-mode formula; [2] Teichholz M-mode formula; [3] subjective estimation of LVEF from two-dimensional echocardiographic videotape; [4] area-length method in one four-chamber view; [5] average of area-length method in three four-chamber views; [6] average of area-length method in four-chamber and two-chamber views (one beat each); [7] subjective estimation from stored videoloop of four-chamber and two-chamber view. In 30 cases M-mode tracings were available for analysis. In only 23 of the 44 patients were the apical views suitable for quantitative analysis. The ERNA ejection fraction was 44 +/- 17% (mean +/- 1 SD). The best echocardiographic correlation with ERNA ejection fraction in each patient subgroup studied was obtained by method 3. We concluded that subjective analysis of the videotaped study by an experienced cardiologist/echocardiographer provided the best estimation of ERNA ejection fraction. More time-consuming and costly computer techniques yielded a worse estimate.

Adult↗
PubMed1989

Unusual phonological behavior and the avoidance of homonymy in children.

Young children sometimes make use of unusual phonological patterns even when they already possess the appropriate sound or a suitable substitute in their phonological systems. In this investigation, we attempted to determine whether in such instances unusual sound changes enable children to avoid potential homonymy with other words in their lexicons. Novel words were presented to children, half serving as potential homonyms, half as unlikely homonyms. The children's acquisition of these words was monitored. For a group of normally developing children, unusual sound changes were found to be more frequent in the words with the potential for homonymy. In contrast, a group of children with specific language impairment showed the same degree of unusual usage for both types of words. The findings suggest that children with specific language impairment are especially limited in their ability to capitalize on the phonetic regularities of the language.

Child, Preschool↗
PubMed1988

Early return to work after uncomplicated myocardial infarction. Results of a randomized trial.

To determine if an occupational work evaluation could shorten the time to return to work, 201 employed men aged 49 +/- 7 years who were recovering from uncomplicated myocardial infarction were randomized to usual care (n = 102) or to an occupational work evaluation (n = 99). The occupational work evaluation consisted of a symptom-limited treadmill test performed 23 +/- 3 days after myocardial infarction and a formal recommendation to the patient and primary physician that the patient return to work within the next two weeks. The groups did not differ in age, medical status, comorbid disease, occupation type, or years on the job. At six months, 92% of patients receiving the intervention and 88% of patients receiving usual care were working either full- or part-time. Return to full-time work occurred at a median of 51 days in patients receiving the intervention and 75 days in patients receiving usual care. This 32% reduction in the convalescence period was associated with +2102 of additional earned salary per intervention patient in the six months after myocardial infarction. One or more recurrent cardiac events occurred in 14 intervention patients (one death, one nonfatal myocardial infarction, three angioplasties, and nine coronary surgeries) and in 13 usual-care patients (two deaths, three nonfatal myocardial infarctions, six angioplasties, and seven coronary surgeries) in the six months after myocardial infarction. The early return to work of low-risk patients based on an occupational work evaluation is associated with important economic benefits.

Attitude to Health↗
PubMed1988

Object transformations in the play of language-impaired children.

The play behavior of 10 language-impaired children was observed. Their performances in play were compared to those of 10 normal-language children matched for chronological age as well as to those of 10 normal-language children matched for mean length of utterance. The children were observed as they played spontaneously with a standard group of toys and as they played with objects that required object transformations for successful play. The chronological age-matched normal subjects showed a trend toward performance of more object transformations in play than either the language-impaired or younger normal-language children. Additionally, although object transformations were observed in both segments, all children performed more object transformations with objects than with toys.

Child↗
PubMed1988

Effect of chronic diabetes on myocardial fuel metabolism and insulin sensitivity.

To assess the effect of chronic insulin-deficient diabetes on myocardial fuel substrate metabolism in vivo, we measured the myocardial balance of glucose, free fatty acids (FFAs), and amino acids in nine postabsorptive conscious dogs 4-6 wk after treatment with streptozocin. The acute effect of insulin on the myocardial balance of these same substrates was measured in six dogs by use of the euglycemic insulin clamp technique. To further examine the effect of insulin on heart amino acid balance, we studied three additional dogs given a constant infusion of amino acids during the insulin clamp to blunt the insulin-induced hypoaminoacidemia. In these dogs, the fasting plasma glucose concentration was markedly elevated (258 +/- 3 mg/dl). In the basal period, there was no significant glucose uptake by the heart [arterial vs. coronary sinus concentration difference (delta) = 1.0 +/- 2.0 mg/dl]; furthermore, physiologic hyperinsulinemia did not stimulate glucose uptake (delta = 2.0 +/- 2.5 mg/dl). Postabsorptively, arterial FFAs were elevated (1550 +/- 320 microM) in diabetic animals, and there was a significant net extraction of FFAs by the heart (net uptake 26 +/- 9 mumol/min; extraction ratio 30 +/- 8%). During the insulin clamp, arterial FFAs declined (645 +/- 240 microM), as did heart FFA uptake (11 +/- 6 mumol/min), and the net extraction ratio for FFAs was unchanged (30 +/- 7%). Similarly, the arterial branched-chain amino acid (BCAA) concentration was elevated in the postabsorptive state, and there was a significant myocardial uptake of these amino acids and of alanine.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗
PubMed1987

Congestive heart failure and left ventricular dysfunction complicating doxorubicin therapy. Seven-year experience using serial radionuclide angiocardiography.

To impact on the development of clinical congestive heart failure as a complication of doxorubicin therapy, left ventricular ejection fraction was monitored with serial resting radionuclide angiocardiography in 1,487 patients with cancer over a seven-year period in both university and community hospital environments. A high-risk subset of 282 patients was selected for retrospective analysis of their clinical outcome. High-risk patients were identified by one or two of the following three criteria: decline of 10 percent or more in absolute left ventricular ejection fraction from a normal baseline to 50 percent or less; high cumulative dose of doxorubicin (more than 450 mg/m2); abnormal baseline left ventricular ejection fraction (less than 50 percent). Clinical congestive heart failure occurred in 46 (16 percent) during the treatment period, and in an additional three patients (1.3 percent) at last follow-up examination 11.8 +/- 14.2 months following discontinuation of doxorubicin. Total cumulative dosages of doxorubicin that precipitated congestive heart failure (75 to 1,095 mg/m2) and those that did not (30 to 880 mg/m2) varied widely. Decline of 10 percent or more in absolute left ventricular ejection fraction to a value of 50 percent or less preceded administration of the final dose of doxorubicin that precipitated clinical congestive heart failure in the majority of patients in whom congestive heart failure developed. Clinical congestive heart failure improved in 87 percent given routine therapy with digitalis, diuretics, and/or vasodilators. Criteria for monitoring left ventricular ejection fraction and discontinuing doxorubicin were formulated. The occurrence of clinical congestive heart failure was compared in those patients whose management was concordant with proposed criteria (Group A) and in those whose management was not (Group B). Group A had a lower incidence of congestive heart failure compared with Group B (2.9 percent versus 20.8 percent, p less than 0.001) and had only mild congestive heart failure that resolved with treatment (n = 2) and no deaths due to congestive heart failure. Multivariate analysis with proportional-hazards regression (Cox's model) demonstrated a fourfold reduction in the incidence of congestive heart failure independent of other clinical predictor variables in those patients whose management was concordant with proposed guideline criteria. The incidence, persistence, late development, predictability, and reversibility of clinical congestive heart failure were comparable in university and community hospital settings.(ABSTRACT TRUNCATED AT 400 WORDS)

Doxorubicin↗
PubMed1986

Dilated cardiomyopathy and cocaine abuse. Report of two cases.

Two young patients with dilated cardiomyopathies associated with long-term use of cocaine are described. A 42-year-old male cocaine abuser with normal coronary arteries experienced recurrent myocardial infarction, with development of a dilated, globally hypocontractile left ventricle. The second patient, a 28-year-old woman with a prominent history of inhaling vaporized cocaine ("free-basing"), presented with symptoms and signs of biventricular heart failure and was found to have a dilated cardiomyopathy. The clinical spectrum of cocaine cardiotoxicity is reviewed, and pathophysiologic mechanisms of cocaine-induced cardiomyopathy are discussed. Long-term cocaine use may cause dilated cardiomyopathy and recurrent myocardial infarction, even in the absence of atherosclerotic epicardial coronary artery disease.

Adult↗