The role of Hsp70 in age-related diseases and the prevention of cancer.

This article focuses on the structure, function, mode of action of one of the major heat shock proteins, Hsp70, and its implication in age-related diseases and cancer.

Effect of exercise on postprandial insulin responses in Mexican American and non-Hispanic women.

Postprandial insulin responses (integrated area under the curve) to an oral glucose load after a period of aerobic exercise and no exercise (control) were compared in sedentary normoglycemic Mexican American and non-Hispanic women pair-matched (n = 9) on total body fat mass (21.8 +/- 3.5 kg). The age (27.4 +/- 3.0 years), body mass index (BMI) (23.6 +/- 1.4 kg/m2), waist to hip ratio (WHR) (0.85 +/- .02), waist circumference (83.5 +/- 4.5 cm), lean mass (36.2 +/- 1.5 kg), and maximal O2 consumption ([VO2 max] 32.9 +/- 1.6 mL x kg(-1) x min(-1)) were similar, although the centrality index (subscapular/triceps skinfolds) was significantly greater in Mexican Americans (0.88 +/- 0.06 v 0.70 +/- 0.05, P < .01). Exercise (treadmill walking for 50 minutes at 70% VO2 max) and control trials were performed 4 weeks apart and 5 to 12 days after the onset of menstruation. A 75-g oral glucose load was administered 15 hours after the completion of each trial, with the subjects 12 hours postprandial. Blood samples were drawn prior to glucose ingestion (fasting, 0 minutes) and at minutes 15, 30, 60, 90, 120, and 150 postingestion. The postprandial insulin response was calculated using a trapezoidal method. In Mexican Americans, significant (P < .02) reductions in the postprandial insulin response (exercise v control, 6.5 +/- 1.0 v 8.5 +/- 1.4 pmol/L x min x 10(4)) and fasting insulin (exercise v control, 77.4 +/- 7.0 v 88.5 +/- 10.3 pmol/L) occurred after exercise compared with the control condition. In non-Hispanics, neither the postprandial insulin response (exercise v control, 7.2 +/- 1.0 v 6.2 +/- 0.9 pmol/L x min x 10(4)) nor fasting insulin (exercise v control, 77.0 +/- 8.2 v 82.9 +/- 8.9 pmol/L) were significantly different between trials. The postprandial insulin response in the control trial was significantly correlated with the change in the insulin response (control minus exercise) in the 18 women (r = .56, P = .01). No trial or group differences were found for postprandial glucose and C-peptide responses. Mexican American women have a high risk of developing type 2 diabetes, and aerobic exercise may be valuable in the prevention or delay of onset of diabetes by reducing peripheral insulin resistance.

Effect of intensity and energy expenditure on postexercise insulin responses in women.

The purposes of the study were to compare insulin responses after rest and exercise of two different intensities and equal total energy expenditure and to examine these responses in normoglycemic women. Twenty-four untrained women (age 23.4 +/- 0.9 yr) completed three randomly assigned treatments over the course of a 3- to 4-wk period: rest, 40% maximal oxygen consumption x 87 min (Low), and 70% maximal oxygen consumption x 50 min (High). Total energy expenditure was 1,821 +/- 61 and 1,692 +/- 59 kJ, heart rate was 119 +/- 2 and 163 +/- 2 beats/min, and oxygen consumption was 17.1 and 27.2 ml.kg-1.min-1 for Low and High, respectively. Fifteen to 17 h posttreatment and 12 h postprandial, each subject drank a 75-g glucose solution (oral glucose tolerance test). Blood samples were drawn before and at 30, 60, 90, 120, and 150 min after ingestion and were analyzed for glucose and insulin. Glucose areas and responses at the same time points across treatments were similar. Area under the insulin curve was significantly lower (P < 0.05) after High (51,864 +/- 3,780 pM x min) compared with rest (61,009 +/- 4,425 pM x min), but Low (59,191 +/- 5,307 pM x min) was not different from either rest or High. The insulin level at the 120-min time point was significantly (P < 0.01) lower after High (290.8 pM) compared with rest (391.7 pM). On the basis of these results, exercise-related changes in insulin responses are more dependent on exercise intensity than on energy expenditure in untrained women.

kappa-Opioid receptor-transfected cell lines: modulation of adenylyl cyclase activity following acute and chronic opioid treatments.

The opioid receptors mu, delta and kappa have recently been cloned. Here we show that kappa-agonists inhibit adenylyl cyclase activity in Chinese hamster ovary cells stably transfected with rat kappa-opioid receptor cDNA. Chronic exposure of the cells to kappa-agonists did not lead to significant desensitization of the capacity of the agonists to inhibit adenylyl cyclase. On the other hand, withdrawal of the agonist following the chronic treatment led to the phenomenon of supersensitivity ('overshoot') of adenylyl cyclase activity. Both the inhibition of adenylyl cyclase activity by the acute opioid treatment and the chronic agonist-induced supersensitivity are pertussis toxin sensitive, demonstrating involvement of Gi/Go proteins in both processes.

The effects of gymnastics training on bone mineral density.

The purpose of this study was to examine the effect of 27 wk of gymnastics training on bone mineral density (BMD), body composition, insulin-like growth factor I (IGF-I), and osteocalcin. Subjects were 11 female intercollegiate gymnasts and 11 controls. Dual energy x-ray absorptiometry (Lunar DPX) was used to determine BMD (L2-L4 and femur) and to assess body composition. The gymnasts were significantly lower in weight (53.9 and 60.8 kg) and % body fat (22.6 and 30.6) compared with controls. After training, body weights of gymnasts remained the same but there was a significant increase in lean tissue mass of 2.9 kg (6.7%, P < 0.05). No changes in body composition were observed in the controls. The gymnasts had significantly higher mean lumbar (1.321 vs 1.225), and femoral neck (1.163 vs 1.079) BMD (g.cm-2) than the controls. Lumbar BMD increased significantly (1.3%) in gymnasts following training but femoral neck BMD did not increase. No BMD changes occurred in the control group. Regarding serum IGF-I, no differences were seen between the groups or across time. Serum osteocalcin values were significantly higher in the gymnasts than the controls, but no differences were found across time. In conclusion, gymnasts had significantly higher BMDs than controls, and a significant increase in lumbar BMD was seen in the gymnasts following 27 wk of training.

Use of reinforcement to increase independence in physical fitness performance of profoundly mentally retarded youth.

The purpose of this study was to examine the influence of verbal praise and verbal praise plus music or vibratory reinforcement on the level of independent performance on abdominal strength and endurance, lower back and hip flexibility, and upper body strength/endurance exercises of 12 profoundly mentally retarded, ambulatory youth, ages 10 to 18 years. A single-subject AB design with a control group was used to assess the difference in performance of physical fitness under the baseline condition of no reinforcement and under the two experimental conditions of verbal praise and verbal praise plus music or vibratory reinforcement. In contrast to previous results reported in the literature, verbal praise and verbal praise plus music or vibratory reinforcement were not effective in increasing the level of independence in performing selected physical fitness tasks.

Influence of selected reinforcers on the cardiorespiratory exercise behavior of profoundly mentally retarded youth.

6 profoundly mentally retarded youth were provided a 5-wk. stair-climbing program to improve cardiorespiratory fitness behavior. Three subjects were provided verbal plus food reinforcement and the other three received verbal reinforcement during the intervention phase. Based on the visual inspection of the data, both types of reinforcement increased the number of steps taken and exercise time.

Covalent binding of protamine by glutaraldehyde to bioprosthetic tissue: characterization and anticalcification effect.

Calcification is the principal cause of the clinical failure of bioprosthetic heart valves (BHV). The hypothesis of this work was that an impaired balance between positively and negatively charged amino acids, due to the reaction with Lys and Hyl tissue-collagen residues, expose affinity sites to Ca++. We further hypothesized that regardless of the cause(s) of BHV calcification, positive charge modification of the tissue will prevent their propensity to calcify. Modification of BHV tissue was obtained by covalently binding protamine sulfate, a polybasic peptide, via glutaraldehyde. The modification procedure resulted in stable, covalent links of approximately 5.3% w/w protamine with undiminished anticalcification properties, even after long storage. Significant prevention of calcification was exhibited by the p-bound tissue in comparison to BHV tissue, 66.0 and 106.5 micrograms/mg calcium, respectively, after 30 days of subdermal implants in rats. The results support our hypotheses, and orthotopical heart valve replacements are required in order to completely evaluate the treatment efficacy and biocompatibility.

Mechanical properties and histology of charge modified bioprosthetic tissue resistant to calcification.

Modification of bioprosthetic heart valves tissue by covalently binding protamine sulphate, results in stable covalent links of protamine to the tissue, conferring resistance to calcification. We report here the morphological evaluation and mechanical properties (elastic modulus and ultimate tensile strength) of protamine-bound bioprosthetic tissue that have high anticalcification potential. Protamine-bound bioprosthetic tissue had significantly higher tissue modulus and ultimate tensile strength values than control tissue groups. However, the mechanical properties and tissue architecture were inferior to those of bioprosthetic tissue.

Prevention of bioprosthetic heart valve tissue calcification by charge modification: effects of protamine binding by formaldehyde.

Calcification is the principal cause of the clinical failure of bioprosthetic heart valves (BHV). Calcification occurs through an interaction of host and implant factors, mainly younger age and glutaraldehyde pretreatment, respectively. The hypothesis of this work was that an impaired balance between positively and negatively charged amino acids, due to the reaction with Lys and Hyl tissue-collagen residues, expose affinity sites to Ca++. We further hypothesized that regardless of the cause(s) of BHV calcification, positive charge modification of the tissues will prevent their propensity to calcify. Modification of BHV tissue was obtained by covalently binding protamine sulfate, a polybasic peptide, via formaldehyde and subsequent glutaraldehyde tissue crosslinking. Protamine-bound tissue exhibited stability properties (shrinkage temperature and resistance to collagenase digestion) similar to BHV tissue. Protamine-treated tissue was less permeable to Ca++, and reduced staining was observed with positively charged dyes, indicating the presence of positively charged functional groups in the modified tissue. Significant prevention of calcification was exhibited by the p-bound tissue in comparison to BHV tissue, 30.9 and 109 micrograms/mg calcium, respectively, after 30 days of subdermal implants in rats. The modification procedure resulted in stable, covalent links of approximately 10% w/w protamine with undiminished anticalcification properties, even after 1 year storage. The results support our hypotheses, and orthotopical heart valve replacements are required in order to completely evaluate the treatment efficacy and biocompatibility.

Step ergometry: is it task-specific training?

Maximal exercise responses were measured before and after 10 weeks of training in two groups of men, one trained on a treadmill (n = 12) and the other on a step ergometer (n = 9); the groups were pre- and post-tested on both machines to examine the specificity of the training modes. Training for both groups consisted of 3 days week-1, 30 min day-1, progressing to 50 min day-1, at an intensity of 75%-80% heart rate maximum reserve. Pre-training maximal oxygen uptake (VO2max) was significantly higher on the treadmill for both groups (X = 8.5%). VO2max increased 6.9% on the treadmill (P less than 0.05) and 6.9% (P greater than 0.05) on the step ergometer after treadmill training. The small increases may be attributed to the specificity of the testing protocols used to elicit VO2max. Significant (P less than 0.01) increases in VO2max were found for both modalities after step-ergometry training (treadmill = 11.8%; step ergometer = 23.2%). These increases resulted in equal post-test VO2max values (4.05 l min-1; 51 ml kg-1 min-1) on the step ergometer and treadmill. The significant increases in VO2max found for both modalities after step-ergometry training shows that (1) step ergometry is an effective training modality, and (2) its effects can be measured on the treadmill and therefore it is not task-specific training.

The effect of training on the norepinephrine response at rest and during exercise in 5 degrees and 20 degrees C environments.

Eleven males were examined at rest and during submaximal exercise in 5 degrees C and 20 degrees C environments to determine if the norepinephrine (NE) and other physiological responses in the cold would be altered by eight weeks of training. Blood samples were obtained at the end of 15 minutes of rest and submaximal exercise, and were assayed for NE. Pretraining resting NE levels in the 5 degrees C condition were significantly higher than those found in the 20 degrees C environment (684 +/- 89 vs 491 +/- 48 pg/ml). A significant training effect reduced resting NE levels in the 5 degrees C (502 +/- 77 pg/ml) but not the 20 degrees C (392 +/- 45 pg/ml) condition. Pre and posttraining exercise NE levels were elevated above resting in both the 5 degrees C (1477 +/- 136 vs 1559 +/- 208) and the 20 degrees C environments (1623 +/- 176 pg/ml vs 1444 +/- 224 pg/ml), but were not significantly different between conditions. Skin temperatures were significantly lower, and resting blood pressure was significantly higher in the 5 degrees C condition. These data suggest that both cold and exercise act as stimulators of NE release, but an additive effect on NE of cold and exercise does not occur. The resting NE levels pre and posttraining in the 5 degrees C condition suggest that a cross tolerance to cold stress was present.

Stair climbing: an alternative exercise modality for firefighters.

The purpose of this investigation was to determine the maximal cardiorespiratory responses of firefighters to stair-climbing work and to compare these responses to maximal treadmill exercise. Thirty-eight firefighters volunteered to participate in the study. Maximal CR including oxygen consumption (VO2), ventilatory equivalent for oxygen (VE/VO2), minute ventilation (VE) and heart rate (HR) were measured during both stair climbing and graded treadmill exercise. The results showed that VO2max and HRmax were significantly lower, 7% and 2% respectively, and the VE/VO2 was significantly higher (6.7%) during the stair-climbing exercise. Maximal VE was not different between the two modes of exercise. The results suggest that since VO2max and HRmax were lower during stair climbing, the metabolic cost of firefighting tasks as related to VO2max on a treadmill may not be accurately reflected. Since stair climbing is a task-specific activity for firefighters, it is recommended that testing of firefighters be performed on a stair-climbing device, and that the difference in VO2max between treadmill and stair-climbing exercise be considered when recommending a desired fitness level for firefighters.

The effect of exercise on plasma somatomedin-C/insulinlike growth factor I concentrations.

Because inadequate intake of energy or protein causes reduction in the plasma concentrations of somatomedin-C/insulinlike growth factor I (Sm-C/IGF-I), we have completed studies to determine whether the energy deficit induced by vigorous exercise sustained for 1 week would also be associated with a reduction in this peptide. When six healthy, exercise-conditioned males were fed a diet consisting of 35 kcal/kg ideal body weight (IBW) and 1.0 g protein/kg and exercised so that 14.1 to 16.3 kcal/kg of energy was expended each day, their plasma Sm-C/IGF-I concentrations declined from a mean basal value of 1.15 +/- 0.78 U/mL (1 +/- SD) to 0.62 +/- 0.41 U/mL during the last two days of a seven-day exercise period (P less than .05). This decrease in Sm-C/IFG-I occurred almost entirely in the first four days of the study period. After 3 weeks for reacclimation, the calorie intake of each volunteer was reduced by the same number of calories as had been expended in the form of exercise during each day of the exercise week (mean of 15.1 kcal/kg IBW/d). On this regimen the mean plasma Sm-C/IGF-I declined from 1.12 +/- 0.57 U/mL, to 0.69 +/- 0.37 U/mL on the last two days of dietary restriction. The magnitude of fall with dietary restriction was not significantly different from that observed during exercise. During the last three days of the exercise period the mean daily nitrogen balance was -1.60 +/- 1.70 g/d, while this value was -3.50 +/- 1.73 g/d during the last three days of dietary restriction (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of coactors on performance of visually impaired runners.

The purpose of this exploratory study was to determine the influence of coactors on the running performance of 13 visually impaired individuals. There was no significant difference for visually impaired sprint runners running alone and with a coactor. The "mere presence" of a coactor was not enough for social facilitation to occur when visual evaluation was not present.

Responses of endurance-trained subjects to caloric deficits induced by diet or exercise.

The purpose of this study was to examine the effect of 7 d of caloric deficit (1,000 kcal X d-1) induced by diet or exercise on weight loss and exercise performance of six endurance-trained males. The diet of each subject was controlled during the weeks preceding the dietary restriction and exercise to normalize nitrogen balance. Weight and blood chemistries were monitored daily. Submaximal and maximal exercise responses were tested at the end of each week. Weight loss during the exercise week was 0.76 kg, significantly less (P less than 0.05) than in the dietary restriction week (-2.16 kg). Seven d of cumulative nitrogen loss was greater (P less than 0.05) during the diet week (-24.5 g) than the exercise week (-11.1 g). Resting hematocrit, hemoglobin, total plasma protein, and albumin were significantly reduced during the exercise week compared to all other weeks. Maximal exercise capacity, measured as VO2 (61 ml X kg-1 X min-1) or duration of exercise, was not affected by either method of caloric deficit, but R values and lactates were lower than controls for both dieting and exercise deficits. The results suggest that endurance-trained individuals lose weight more slowly and conserve more protein when using exercise to induce a caloric deficit compared to dietary restriction. The results also suggest the possibility of the sequestering of blood proteins to supplement muscle protein synthesis during periods of exercise-induced caloric deficits.