Limb venous compliance responses to lower body negative pressure in humans with high blood pressure.

This study tested the hypothesis that limb venous responses to baroreceptor unloading are altered in individuals with high blood pressure (HBP) compared with normotensive (NT) controls. Calf venous compliance was assessed in 20 subjects with prehypertension and stage-1 hypertension (mean arterial pressure, MAP: 104±1 mm Hg) and 13 NT controls (MAP: 86±2 mm Hg) at baseline and during lower body negative pressure (LBNP), using venous occlusion plethysmography. Baroreflex sensitivity (BRS) was measured using the sequence technique and total peripheral resistance (TPR) was estimated from finger plethysmography. Baseline venous compliance was not different between groups, but the HBP group had lower baseline lnBRS (2.22±0.14 vs 2.7±0.18 ms mm Hg(-1)) and greater baseline TPR (3828±138 vs 3250±111 dyn sec(-1) cm(-5) m(2), P<0.05). Calf venous compliance was reduced in response to LBNP only in the NT group (P<0.05). The HBP group had a greater increase in TPR (ΔTPR) compared with the NT group (+1649±335 vs +718±196 dyn sec(-1) cm(-5) m(2), P<0.05). In conclusion, the early stages of hypertension are characterized by an attenuated venoconstrictor response to baroreceptor unloading, which may compensate for an exaggerated vasoconstrictor response and protect against further increases in blood pressure.

Plasticity of heart rate signalling and complexity with exercise training in obese individuals with and without type 2 diabetes.

OBJECTIVE: To examine the responsiveness of cardiac autonomic function and baroreflex sensitivity (BRS) to exercise training in obese individuals without (OB) and with type 2 diabetes (ObT2D). DESIGN: Subjects were tested in the supine position and in response to a sympathetic challenge before and after a 16-week aerobic training program. All testing was conducted in the morning following a 12-h fast. SUBJECTS: A total of 34 OB and 22 ObT2D men and women (40-60 years of age) were studied. MEASUREMENTS: Heart rate variability (HRV) was measured at rest via continuous ECG (spectral analysis with the autoregressive approach) and in response to upright tilt. The dynamics of heart rate complexity were analyzed with sample entropy and Lempel-Ziv entropy, and BRS was determined via the sequence technique. Subjects were aerobically trained 4 times per week for 30-45 min for 16 weeks. RESULTS: Resting HR decreased and total power (lnTP, ms(2)) of HRV increased in response to exercise training (P<0.05). High frequency power (lnHF) increased in OB subjects but not in OBT2D, and no changes occurred in ln low frequency/HF power with training. Upright tilt decreased lnTP and lnHF and increased LF/HF (P<0.01) but there were no group differences in the magnitude of these changes nor were they altered with training in either group. Tilt also decreased complexity (sample entropy and Lempel-Ziv entropy; P<0.001), but there was no group or training effect on complexity. BRS decreased with upright tilt (P<0.01) but did not change with training. Compared to OB subjects the ObT2D had less tilt-induced changes in BRS. CONCLUSION: Exercise training improved HRV and parasympathetic modulation (lnHF) in OB subjects but not in ObT2D, indicating plasticity in the autonomic nervous system in response to this weight-neutral exercise program only in the absence of diabetes. HR complexity and BRS were not altered by 16 weeks of training in either OB or ObT2D individuals.

Short-term exercise training improves aerobic capacity with no change in arterial function in obesity.

The aim of the study is to determine the effects of short-term high-intensity exercise on arterial function and glucose tolerance in obese individuals with and without the metabolic syndrome (MetSyn). Obese men and women (BMI > 30 kg/m(2); 39-60 years) with and without MetSyn (MetSyn, n = 13; Non-MetSyn, n = 13) participated in exercise training consisting of ten consecutive days of treadmill walking for 1 h/day at 70-75% of peak aerobic capacity. Changes in aerobic capacity, flow-mediated dilation (FMD), and arterial stiffness using central and peripheral pulse wave velocity (PWV) measurements were assessed pre- and post-training. These measurements were obtained fasting and 1-h post-test meal while the subjects were hyperglycemic. Aerobic capacity improved for both groups [Non-MetSyn 24.0 +/- 1.6 vs. 25.1 +/- 1.5 mL/(kg min); MetSyn 25.2 +/- 1.8 vs. 26.2 +/- 1.7 mL/(kg min), P < 0.05]. There was no change in body weight. FMD decreased by ~20% (P < 0.05) for both groups during acute hyperglycemia (MetSyn, n = 11; Non-MetSyn, n = 10), while hyperglycemia increased central PWV and not peripheral PWV. Exercise training did not change FMD in the fasted or challenged state. Central and peripheral PWV were not altered with training for either group (MetSyn, n = 13; Non-MetSyn, n = 13). A 10-day high-intensity exercise program in obese individuals improved aerobic capacity and glucose tolerance but no change in arterial function was observed. Acute hyperglycemia had a deleterious effect on arterial function, suggesting that persons with impaired glucose homeostasis may experience more opportunities for attenuated arterial function on a daily basis which could contribute to increased cardiovascular risk.

Cardiac autonomic function and baroreflex changes following 4 weeks of resistance versus aerobic training in individuals with pre-hypertension.

AIM: Cardiac autonomic modulation and baroreflex sensitivity (BRS) are altered in individuals with hypertension. Aerobic exercise (AE) training has been shown to improve both measures, yet little is known about the effects of resistance exercise (RE). The purpose of this study was to examine the heart rate variability (HRV) and BRS following 4 weeks of resistance or aerobic training in a population with borderline high blood pressure (BP). METHODS: Twenty-nine mild hypertensives were recruited and randomly assigned to 4 weeks of RE or AE training. Before and after training, resting measures of HRV frequencies and BRS were obtained. RESULTS: There was a significant decrease in resting systolic BP for both exercise training modes (RE 136 +/- 3.0 pre- to 132 +/- 3.4 post-training vs. AE 142 +/- 4.0 pre- to 137 +/- 3.6 mmHg post-training, P = 0.019). Diastolic BP decreased significantly following both exercise training modes (RE 78 +/- 1.31 pre to 74 +/- 1.1 post vs. AE 80 +/- 1.7 pre to 77 +/- 1.6 mmHg post, P = 0.002). A significant time by training mode interaction for low frequency : high frequency (HF) ratio (P = 0.017) with AE decreasing the ratio (275.21 +/- 67.28 to 161.26 +/- 61.49) and RE increasing this ratio (143.73 +/- 65.00 to 227.83 +/- 59.41). Natural log-transformed (ln) HRV values showed a time-by-training mode interaction for ln HF (P = 0.05) as ln HF increased (4.7 +/- 0.38 to 5.4 +/- 0.35 ms(2)) following AE and decreased (5.98 +/- 0.37 to 5.76 +/- 0.42 ms(2)) following RE. BRS increased following aerobic training and decreased after resistance training (6.74 +/- 1.2 to 7.94 +/- 1.3 and 10.44 +/- 1.2 to 9.1 +/- 1.2 ms mmHg(-1) respectively, P = 0.021). CONCLUSIONS: Aerobic exercise improved the autonomic nervous system (increasing vagal tone, reducing sympathovagal balance while increasing BRS) while RE showed no improvements in cardiac autonomic tone and decreased BRS.

Effect of 4 weeks of aerobic or resistance exercise training on arterial stiffness, blood flow and blood pressure in pre- and stage-1 hypertensives.

The benefits of aerobic exercise (AE) training on blood pressure (BP) and arterial stiffness are well established, but the effects of resistance training are less well delineated. The purpose of this study was to determine the impact of resistance vs aerobic training on haemodynamics and arterial stiffness. Thirty pre- or stage-1 essential hypertensives (20 men and 10 women), not on any medications, were recruited (age: 48.2 +/- 1.3 years) and randomly assigned to 4 weeks of either resistance (RE) or AE training. Before and after training, BP, arterial stiffness (pulse wave velocity (PWV)) and vasodilatory capacity (VC) were measured. Resting systolic BP (SBP) decreased following both training modes (SBP: RE, pre 136 +/- 2.9 vs. post 132 +/- 3.4; AE, pre 141 +/- 3.8 vs. post 136 +/- 3.4 mm Hg, P = 0.005; diastolic BP: RE, pre 78 +/- 1.3 vs post 74 +/- 1.6; AE, pre 80 +/- 1.6 vs. post 77 +/- 1.7 mm Hg, P = 0.001). Central PWV increased (P = 0.0001) following RE (11 +/- 0.9-12.7 +/- 0.9 ms(-1)) but decreased after AE (12.1 +/- 0.8-11.1 +/- 0.8 m s(-1). Peripheral PWV also increased (P = 0.013) following RE (RE, pre 11.5 +/- 0.8 vs. post 12.5 +/- 0.7 ms(-1)) and decreased after AE (AE, pre 12.6 +/- 0.8 vs post 11.6 +/- 0.7 m s(-1)). The VC area under the curve (VC(AUC)) increased more with RE than that with AE (RE, pre 76 +/- 8.0 vs. post 131.1 +/- 11.6; AE, pre 82.7 +/- 8.0 vs. post 110.1 +/- 11.6 ml per min per s per 100 ml, P = 0.001). Further, peak VC (VCpeak) increased more following resistance training compared to aerobic training (RE, pre 17 +/- 1.9 vs. post 25.8 +/- 2.1; AE, pre 19.2 +/- 8.4 vs post 22.9 +/- 8.4 ml per min per s per 100 ml, P = 0.005). Although both RE and AE training decreased BP, the change in pressure may be due to different mechanisms.

Hormone-replacement therapy use, but not race, impacts the resting and exercise-induced GH response in postmenopausal women.

OBJECTIVE: This study examined the effect of hormone-replacement therapy (HRT) use on the incremental GH response to aerobic exercise in postmenopausal women and established whether racial differences in the GH response were seen at rest and in response to exercise. METHODS: 13 white (n = 6, HRT; n = 7, no HRT) and seven black women (no HRT) were studied on two occasions, a control day and an exercise day (30 min at 70% VO(2)max on a cycle ergometer). Blood was sampled every 10 min for a 4-h period and analyzed for GH using an ultrasensitive chemiluminescent assay. RESULTS: The mean 4-h GH concentration was higher on both study days in the HRT women than the non-HRT users. The integrated GH concentrations were greater in the HRT women both at rest and in response to exercise (rest, 352 +/- 53 min microg l(-1); exercise, 711 +/- 57 min microg l(-1); P < 0.01) than in the non-HRT women (rest, 157 +/- 87 min microg l(-1); exercise, 248 +/- 94 min microg l(-1)). The incremental GH response was greater in the HRT users than in the non-HRT women (358 +/- 130 versus 90.8 +/- 94 min microg l(-1), respectively; P < 0.05). GH-production rate during the 4-h period was greater in the HRT women than in the non-HRT women (P < 0.01), due to an increase in the GH mass secreted/pulse (P < 0.05), with no change in GH pulse number or GH half-life. No racial differences in the mean 4-h GH concentrations or integrated GH concentrations were found at rest or in response to exercise. CONCLUSION: HRT use resulted in a greater incremental exercise response compared with non-HRT users, due to changes in the secretory pulse characteristics in the HRT users. This study also demonstrated that no racial differences exist at rest and in response to exercise in the morning hours.

Exercise is required for visceral fat loss in postmenopausal women with type 2 diabetes.

This study examined the effects of aerobic exercise without weight loss, a hypocaloric high monounsaturated fat diet, and diet plus exercise (D+E) on total abdominal and visceral fat loss in obese postmenopausal women with type 2 diabetes. Thirty-three postmenopausal women (body mass index, 34.6 +/- 1.9 kg/m(2)) were assigned to one of three interventions: a hypocaloric high monounsaturated fat diet alone, exercise alone (EX), and D+E for 14 wk. Aerobic capacity, body composition, abdominal fat distribution (magnetic resonance imaging), glucose tolerance, and insulin sensitivity were measured pre- and postintervention. Body weight ( approximately 4.5 kg) and percent body fat ( approximately 5%) were decreased (P < 0.05) with the D and D+E intervention, whereas only percent body fat ( approximately 2.3%) decreased with EX. Total abdominal fat and sc adipose tissue (SAT) were reduced with the D and D+E interventions (P < 0.05), whereas visceral adipose tissue (VAT) decreased with the D+E and EX intervention, but not with the D intervention. EX resulted in a reduction in total abdominal fat, VAT, and SAT (P < 0.05) despite the lack of weight loss. The reductions in total abdominal fat and SAT explained 32.7% and 9.7%, respectively, of the variability in the changes in fasting glucose levels, whereas the reductions in VAT explained 15.9% of the changes in fasting insulin levels (P < 0.05). In conclusion, modest weight loss, through either D or D+E, resulted in similar improvements in total abdominal fat, SAT, and glycemic status in postmenopausal women with type 2 diabetes; however, the addition of exercise to diet is necessary for VAT loss. These data demonstrate the importance of exercise in the treatment of women with type 2 diabetes.

Influence of resistance exercise training on glucose control in women with type 2 diabetes.

The objective of the study was to evaluate the effects of acute and chronic resistance training on glucose and insulin responses to a glucose load in women with type 2 diabetes. Subjects consisted of type 2 diabetic women (n = 7) and age-matched controls (n = 8) with normal glucose tolerance. All subjects participated in 3 oral glucose tolerance tests: pretraining, 12 to 24 hours after the first exercise session (acute) and 60 to 72 hours after the final training session (chronic). Exercise training consisted of a whole body resistance exercise program using weight-lifting machines 3 days per week for 6 weeks. Resistance training was effective in increasing strength of all muscle groups in all subjects. Integrated glucose concentration expressed as area under the curve (AUC) was 3,355.0 +/- 324.6 mmol/L. min pretraining, improved significantly (P <.01) after the acute bout of exercise (2,868 +/- 324.0 mmol/L. min), but was not improved with chronic training (3,206.0 +/- 337.0 mmol/L. min) in diabetic subjects. A similar pattern of significance was observed with peak glucose concentration (pre: 20.2 +/-1.4 mmol/L; acute: 17.2 +/- 1.7 mmol/L; chronic: 19.9 +/- 1.7 mmol/L). There were no significant changes in insulin concentrations after any exercise bout in the diabetic subjects. There were no changes in glucose or insulin levels in control subjects. An acute bout of resistance exercise was effective in improving integrated glucose concentration, including reducing peak glucose concentrations in women with type 2 diabetes, but not age-matched controls. There were no significant changes in insulin concentrations for either group. Resistance exercise offers an alternative to aerobic exercise for improving glucose control in diabetic patients. To realize optimal glucose control benefits, individuals must follow a regular schedule that includes daily exercise.

Adrenocortical responses to submaximal exercise in postmenopausal black and white women.

The purpose of this study was to determine whether racial differences exist in the dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), and cortisol concentrations of black and white postmenopausal women at rest and in response to submaximal exercise. Twenty-three postmenopausal women (13 white and 10 black) were studied on 2 occasions. On one occasion subjects rested quietly for 4 hours (control day), whereas on the other occasion after 50 minutes of rest, subjects exercised at 70% of Vo(2) peak for 30 minutes on a cycle ergometer (exercise day). Blood was sampled at rest, during exercise, and during recovery and assayed for DHEA, DHEAS, and cortisol concentrations. Resting DHEA and cortisol concentrations and integrated area under the curve (AUC) were similar between the black and white women; however, the black women had lower resting DHEAS concentrations compared with the white women (DHEAS, black: 1.32 +/- 0.29 v white: 2.18 +/- 0.25 micromol. L(-1), P <.05). Regardless of race, DHEA and cortisol AUC increased significantly above resting values (P <.01), but the exercise AUC for DHEA and cortisol were not different between the black and white women (DHEA: 607 +/- 133 and 824 +/- 108 min x nmol. L(-1); cortisol: 9,604 +/- 1,247 and 8,076 +/- 1,093 min x nmol. L(-1), respectively). No exercise-induced change in integrated DHEAS AUC was found in either group. In conclusion, racial differences exist in the resting DHEAS levels of postmenopausal women, but with no racial differences in resting DHEA and cortisol concentrations. Race had no impact on these adrenal hormone responses to submaximal exercise.

Resting leptin responses to acute and chronic resistance training in type 2 diabetic men and women.

PURPOSE: To evaluate the plasma leptin levels approximately 24 h post-exercise in control and type 2 diabetic subjects and to establish if observed changes in leptin concentrations were acute or chronic effects of a resistance training program. METHODS: Thirty men and women (17 controls and 13 type 2, obese diabetics, age 40-55 y) had resting blood samples drawn at 08:00 h (12 h postprandial) at the beginning of the study (pre-training), 24 h after a three repetition maximal weight lifting bout (acute) and 72 h after their last training bout of 6 weeks of resistance training (chronic). The two groups were not matched with respect to body mass index and the control subjects were not normal weight. Subjects weight-trained three times a week, for 6 weeks, for 1 h, training both the upper and lower body. RESULTS: Serum leptin concentrations were significantly higher in the type 2 diabetics than in the control group at pre-training (41.4+/-8.9 vs 11.4+/-3.0 ng/ml, P<0.05, respectively). Compared to pre-training, the leptin levels decreased significantly (P<0.01) after acute exercise in the diabetics but not in the control subjects (diabetics 30.9+/-7.1 vs controls 10.6+/-2.6 ng/ml). Approximately 72 h after 6 weeks of exercise training, the leptin concentrations were no longer lower than the pre-training values in either group (36.9+/-8.8 vs 11.9+/-8.8 ng/ml, respectively, P=NS). When leptin concentrations were log transformed and adjusted for fat mass there were still significant changes in leptin levels over time and between the control and diabetic group (P<0.05). CONCLUSIONS: The type 2 diabetics showed a significant 30% reduction in resting leptin levels 24 h after a single bout of resistance exercise. This was an acute response to resistance exercise and not a chronic training effect (no difference between pre-training and chronic). The decreased resting leptin concentrations approximately 24 h post-acute exercise may be due to reduced glucose availability to the adipose tissue, particularly in the diabetic subjects. There is no chronic effect of resistance exercise on leptin concentrations.

Determinants of physical functioning in coronary patients: response to cardiac rehabilitation.

BACKGROUND: Coronary heart disease is a major cause of disability. There has been little study of the effect of cardiac rehabilitation on measures of self-reported physical functioning. METHODS: Physical functioning was measured using the Medical Outcomes Study-Short-Form Questionnaire. Determinants of physical function were analyzed in 303 patients with coronary heart disease. Response of physical function to a 3-month exercise rehabilitation program was then determined. RESULTS: At baseline, women had lower physical function scores than men, despite similar age and diagnostic distribution. Older patients had lower physical function than younger patients. Aerobic exercise capacity, leg and arm strength, and comorbidity and depression scores were all significant predictors of baseline physical function (r range, 0.46 to -0.22). Physical function score increased significantly after exercise conditioning, with a mean (+/- SD) overall score increase from 66 +/- 23 to 80 +/- 20 on a scale of 0 to 100. The best baseline determinant of a favorable physical function improvement after rehabilitation was a low baseline physical function score. The best training-related correlate of improved physical function score was a decrease in mental depression score. CONCLUSIONS: Self-reported physical function in coronary patients is related to age, sex, fitness, and mood state. Physical functioning improves after cardiac rehabilitation in all age, sex, and diagnostic groups, but particularly in patients with low baseline values. These data support the concept that cardiac rehabilitation effectively prevents and treats cardiac disability.

Lipid lowering in the cardiac rehabilitation setting.

PURPOSE: The authors determined the frequency and effectiveness of pharmacologic lipid lowering, guided by the recommendations of the National Cholesterol Education Program (NCEP) before and after institution of a systematic lipid assessment performed at the time of the cardiac rehabilitation entry evaluation. METHODS: The systematic lipid evaluation included a full lipid profile and a dietary evaluation at which time an active approach to pharmacologic lipid therapy was taken. Therapy was guided by the NCEP guidelines, with the collaboration of the referring physician. The frequency of lipid therapy change (starting or changing therapy) from the baseline evaluation to a 3-month follow-up visit was the primary study outcome variable. The control group consisted of 51 patients with coronary heart disease (CHD) seen in 1995 at cardiac rehabilitation, who agreed to have their serum lipids measured in a double-blinded fashion. There was no systematic lipid lowering intervention. The intervention group consisted of 187 patients with CHD who participated in cardiac rehabilitation in 1996 to 1997. RESULTS: At baseline, a similar percentage of patients in each group were on lipid lowering therapy: 38% (19/51) in controls versus 35% (65/187) in intervention patients. Among patients with a baseline low-density lipoprotein (LDL) cholesterol of > or = 130 mg/dL, therapy was modified in 18% (4/22) of control patients compared with 52% (35/68) of intervention patients (P < 0.05). Among patients with a baseline LDL cholesterol of > or = 160, therapy was altered in 22% (2/9) control patients compared with 72% (18/25) intervention patients (P < 0.01). In both risk strata of > or = 130 mg/dL and > or = 160 mg/dL, LDL cholesterol measures were lowered to a greater degree in the intervention group. CONCLUSIONS: The performance of a systematic lipid review at the time of cardiac rehabilitation entry, with an active stance toward pharmacologic therapy, results in a threefold increase in pharmacologic modifications and lower LDL cholesterol values for cardiac rehabilitation participants.

Gender differences in cardiac rehabilitation.

It is now widely recognized that comprehensive cardiac rehabilitation has substantial benefits in patients with cardiovascular disease. Despite the fact that cardiovascular disease is the leading cause of death for women in the United States with more than 250,000 deaths each year, most studies of cardiac rehabilitation have not included a substantial number of women. By making cardiac rehabilitation programs more responsive to the needs and goals of female coronary patients, participation rates and compliance rates should increase with a favorable impact on morbidity, mortality, and quality of life for women with cardiovascular diseases.

StrateGene: object-oriented programming in molecular biology.

This paper describes some of the ways that object-oriented programming methodologies have been used to represent and manipulate biological information in a working application. When running on a Xerox 1100 series computer, StrateGene functions as a genetic engineering workstation for the management of information about cloning experiments. It represents biological molecules, enzymes, fragments, and methods as classes, subclasses, and members in a hierarchy of objects. These objects may have various attributes, which themselves can be defined and classified. The attributes and their values can be passed from the classes of objects down to the subclasses and members. The user can modify the objects and their attributes while using them. New knowledge and changes to the system can be incorporated relatively easily. The operations on the biological objects are associated with the objects themselves. This makes it easier to invoke them correctly and allows generic operations to be customized for the particular object.

MRIDIR--a system for integrating research databases.

Lederle's Medical Research Integrated Database Information Retrieval (MRIDIR) system provides timely and facile access to a growing body of computerized, in-house data relating to pharmaceutical discovery and development. It was created in response to a proliferation of special-purpose programs, each dealing with a specific dataset and each with its own query syntax. Written in FORTRAN and interfacing to the System-1022 Database Management System, MRIDIR provides relational links between these datasets and, from the user's viewpoint, integrates them into a single database with a simple query language. A special dataset called the "data dictionary" describes these linkages, and alterations to the database structure (eg, addition of new datasets) are smoothly accomplished through changes to the data dictionary.

The intelligibility of whitened and amplitude compressed speech in a multitalker background.

This experiment determined the effects of amplitude compression on speech intelligibility when both a target speech signal and a competing message were whitened and amplitude compressed. The target CNC discrimination words were electrically mixed with a competing message composed of five talkers. This composite signal was presented to normal hearing subjects in four ways: unmodified, whitened, whitened pplus 3:1 amplitude compression and whitened plus 10:1 amplitude compression. Discrimination functions were obtained for the CNC material by varying the signal-to-competition ratio. The unmodified and whitened speech yielded comparable discrimination functions, but reduced discrimination scores were obtained with the whitened lus compressed speech. However, the reduction in speech discrimination for the whitened plus compressed speech was slight and was most evident when the target signal and the competing background were at the same intensity.

Effects of whitening and peak-clipping on speech intelligibility in the presence of a competing message.

The purpose of this experiment was to determine the effects of peak clipping on speech intelligibility when both a target speech and a competing message were simultaneously peak-clipped. A competing message composed of 5 talkers was electrically mixed with CNC discrimination words. This composite signal was presented to normally hearing subjects in three ways: unmodified, whitened, and whitened and peak-clipped. Discrimination functions were obtained for the CNC material by varying the signal-to-competition ratio. Under these conditions, essentially identical discrimination functions were yielded by the unmodified and whitened speech, whereas substantially reduced discrimination scores were obtained with the whitened/clipped speech. These results would suggest that speech intelligibility is reduced by whitening and peak clipping when more than one talker is present. This is true even though earlier studies have shown that whitening and peak clipping do not reduce speech intelligibility when only a single talker is present. Such a finding has implications for wearable amplification.

The intelligibility of whitened and peak clipped speech.

Consonant-nucleus-consonant monosyllabic words were filltered such that each spectral component had equal energy (i.e., "whitened") and peak clipped in one of four ways: minimal, 20, 30, and 40 dB of clipping. In addition, unmodified consonant-nucleus-consonant words were used as stimuli. These different types of sppech were presented to 20 persons with normal hearing at various sensation levels. The results indicate that whitening and peak clipping do not substantially degrade speech intelligibility. In fact, under some conditions whitening and peak clipping may slightly enhance intelligibility.

Masking level differences encountered in clinical populations.

Methods for measuring masking level differences (MLDs) at 500 Hz and for spondees were used with 290 subjects: 50 persons with normal hearing and 240 patients with various diseases. Of particular interest was whether techniques currently in clinical use could be used with ease, dispatch, and profit in determining MLD size. The methods selected, which were variations of Békésy audiometry and speech reception threshold procedures, proved clinically feasible. Results revealed differences in behavior from one group of subjects to another. Although MLDs were not affected by cortical lesions, they were very often abnormally small for patients with eight-nerve tumor, Meniére's disease, or multiple sclerosis. The high incidence of abnormally small MLDs in populations with normal sensitivity to pure tones and speech but with evidence of subcortical central lesions, such as patients with multiple sclerosis, suggests that the MLD tasks can be of diagnostic value in detecting retrocochlear lesions. However, in persons with hearing loss or significant interaural differences in threshold sensitivity, or both, the MLD tests are not always reliable in differentiating cochlear from retrocochlear disease.