A novel multimodular methodology to investigate external cervical tooth resorption.

AIM: To introduce a multimodular combination of techniques as a novel minimal invasive approach to investigate efficiently and accurately external cervical resorption (ECR). METHODOLOGY: One case of a central incisor with extensive external cervical resorption was selected to demonstrate the potential of a comparative novel study methodology. ECR diagnosis was based on clinical inspection, digital radiography and cone-beam computed tomography (CBCT). After extraction, the tooth was investigated using microfocus computed tomography (micro-CT), nano-CT and hard tissue histology. These techniques were compared for their accuracy and applicability to highlight their advantages and disadvantages. RESULTS: Nano-CT was more effective than micro-CT and CBCT for detailed ex vivo exploration of ECR. The reparative tissue, pericanalar resorption resistant sheet (PRRS), pulp tissue reactions, resorption channels and their interconnection with the periodontal ligament space were accurately visualized by detailed processing and analysis of the nano-CT data set with Dataviewer and CTAn software. Nano-CT analysis provided better insight in the true extent of the resorption, based on quantitative measurements and 3D visualization of the tooth structure. Nano-CT imaging results were similar to hard tissue histology at the mineralized tissue level. To clarify the dynamic phenomenon of reparative tissue formation and substitution of the resorbed tissues, nano-CT needed to be associated with hard tissue histology. CONCLUSION: Nano-CT is a fast and minimal invasive technique for the ex vivo analysis and understanding of ECR and is complementary with hard tissue histology. A combined approach of clinical and CBCT examination, with nano-CT and histological mapping measurements, can provide an ideal platform for future ECR imaging and exploration studies.

Prediction of permeability of regular scaffolds for skeletal tissue engineering: a combined computational and experimental study.

Scaffold permeability is a key parameter combining geometrical features such as pore shape, size and interconnectivity, porosity and specific surface area. It can influence the success of bone tissue engineering scaffolds, by affecting oxygen and nutrient transport, cell seeding efficiency, in vitro three-dimensional (3D) cell culture and, ultimately, the amount of bone formation. An accurate and efficient prediction of scaffold permeability would be highly useful as part of a scaffold design process. The aim of this study was (i) to determine the accuracy of computational fluid dynamics (CFD) models for prediction of the permeability coefficient of three different regular Ti6Al4V scaffolds (each having a different porosity) by comparison with experimentally measured values and (ii) to verify the validity of the semi-empirical Kozeny equation to calculate the permeability analytically. To do so, five CFD geometrical models per scaffold porosity were built, based on different geometrical inputs: either based on the scaffold's computer-aided design (CAD) or derived from 3D microfocus X-ray computed tomography (micro-CT) data of the additive manufactured (AM) scaffolds. For the latter the influence of the spatial image resolution and the image analysis algorithm used to determine the scaffold's architectural features on the predicted permeability was analysed. CFD models based on high-resolution micro-CT images could predict the permeability coefficients of the studied scaffolds: depending on scaffold porosity and image analysis algorithm, relative differences between measured and predicted permeability values were between 2% and 27%. Finally, the analytical Kozeny equation was found to be valid. A linear correlation between the ratio Φ(3)/S(s)(2) and the permeability coefficient k was found for the predicted (by means of CFD) as well as measured values (relative difference of 16.4% between respective Kozeny coefficients), thus resulting in accurate and efficient calculation of the permeability of regular AM scaffolds.

Probing molecular interaction between concanavalin A and mannose ligands by means of SFM.

Recently, the scanning force microscope (SFM) has been widely used for direct monitoring of specific interactions between biologically active molecules. Such studies have employed the SFM liquid-cell setup, which allows measurements to be made in the native environment with force resolution down to a tenth of a picoNewton. In this study, the ligand-receptor strength of monoclonal anti-human prostatic acid phosphatase and prostatic acid phosphatase, representing an antigen-antibody system with a single type of interaction, was determined. Then, the interaction force occurring between concanavalin A and the carbohydrate component of the glycoproteins arylsulfatase A and carboxypeptidase Y was measured. High mannose-type glycans were sought on the human prostate carcinoma cell surface. Application of an analysis based on the Poisson distribution of the number of bonds formed in all these measured systems allowed the strength of the molecular interaction to be calculated. The values of the force acting between two single molecules were 530+/-25, 790+/-32, and 940+/-39 pN between prostatic acid phosphatase and monoclonal anti-human prostatic acid phosphatase, between concanavalin A and arylsulfatase A, and between concanavalin A and carboxypeptidase Y, respectively. The value calculated from data collected for the force between concanavalin A and mannose-containing ligands present on the surface of human prostate carcinoma cells was smaller, 116+/-17 pN. The different values of the binding force between concanavalin A and mannose-containing ligands were attributed to the structural changes of the carbohydrate components.

Oral arginine does not stimulate basal or augment exercise-induced GH secretion in either young or old adults.

BACKGROUND: Growth hormone (GH) helps maintain body composition and metabolism in adults. However, basal and peak GH decline with age. Exercise produces a physiologic GH response that is subnormal in elderly people. Arginine (Arg) infusion can augment GH secretion, but the efficacy of oral Arg to improve GH response to exercise has not been explored. We investigated whether oral Arg increases GH secretion in young and old people at rest and during exercise. METHODS: Twenty young (Y: 22.1 +/- 0.9 y; SEM) and 8 old (O: 68.5 +/- 2.1 y) male and female subjects underwent three different trials following determination of their one-repetition maximum strength (1-RM); exercise only (EO; 3 sets, 8-10 reps at 85% of 1-RM; on 12 separate resistive lifts), Arg only (5.0 g), or Arg + exercise. Blood samples were collected between successive lifts, and GH (ng x ml(-1)) was determined via RIA. RESULTS: In Y vs O: Basal GH secreted (area under the curve) was 543.6 +/- 84.0 vs 211.5 +/- 63.0. During EO, values were 986.6 +/- 156.6 and 517.8 +/- 85.5. Both were significantly lower in the older individuals (p < .05). Oral Arg alone did not result in any increase in GH secretion at rest (310.8 +/- 73.2 vs 262.9 +/- 141.2). When Arg was coadministered during exercise, GH release was not affected in either the young or old and appeared to be blunted in the young compared to the exercise only trial in the young. CONCLUSION: Based upon these findings, we concluded that oral Arg does not stimulate GH secretion and may impair GH release during resistive exercise.

Effect of muscle strength and movement speed on the biomechanics of rising from a chair in healthy elderly and young women.

The ability to rise from a chair is an important task of daily living that is difficult for many elderly individuals to perform, and is particularly challenging when performed quickly. It is important to understand what factors limit performance of the task in older people, so that effective remedial approaches can be developed. In this study, we quantified lower-extremity muscle strength and chair-rise biomechanics in 12 young and 26 healthy elderly women during chair rise at normal and fast speeds without use of the hands. We found that hip and knee extensor torques, vertical and horizontal momentum, and vertical and horizontal ground reaction forces increased in the same way with speed for all subjects. All subjects increased their speed from normal to fast trials, but the young subjects were able to rise more quickly in the fast trials. In the normal speed trials, elderly subjects generated more trunk flexion and horizontal momentum while still in contact with the chair. Muscle activity patterns were similar for all subjects except that the elderly activated the ankle extensors earlier than the young. Although the elderly subjects were much weaker relative to body weight than the young subjects (48.5+/-14.1%), they were able to generate sufficient torques to perform the task. However, age-related differences suggest that chair-rise biomechanics were affected by the reduction in muscle strength, and that strength training regimes, particularly for the hip musculature, may be important to maintain chair-rise ability in the elderly. Copyright 1998 Elsevier Science B.V.

Comparative effects of high- and low-intensity resistance training on thigh muscle strength, fiber area, and tissue composition in elderly women.

The effects of 52 weeks resistance training at one of two exercise intensities on thigh muscle strength, fiber cross-sectional area (CSA), and tissue composition were studied in healthy 65-79-year-old women. Subjects were assigned to either a control (CO), high-intensity (HI) or low-intensity (LO) training group. Exercise regimens consisted of three sets of leg press, knee extension, and knee flexion exercises, 3 days/week, at either 80% of one-repetition maximum (1-RM) for seven repetitions (HI) or 40% of 1-RM for 14 repetitions (LO). Dynamic muscle strength was evaluated by 1-RM, thigh lean tissue mass (LTM), fat mass, and bone mineral density (BMD, g/cm2) by dual energy X-ray absorptiometry, and fiber CSA of vastus lateralis m. by histomorphometry. Muscle strength increased, on average (+/- SEM), by 59.4 +/- 7.9% and 41.5 +/- 7.9% for HI and LO, respectively, compared to 1.3 +/- 4.8% in CO (P = 0.0001). Type I fiber CSA increased over time (P < 0.05) in both exercise groups, with a trend for increased type II area (HI, P = 0.06; LO, P = 0.11). There was no significant effect of either exercise program on thigh tissue composition, except for BMD at the 1/3 site (middle third of the femur), where LO and CO groups experienced a decline (P < 0.05) of -2.2 +/- 0.5% and -1.8 +/- 0.6%, respectively, while HI maintained BMD (+1.0 +/- 1.0%). Both training programs produced significant gains in thigh muscle strength, which were associated with fiber hypertrophy, although these did not translate into appreciable alterations in thigh tissue composition.

Effect of a sustained program of resistance training on the acute growth hormone response to resistance exercise in older adults.

We have previously shown that an episode of resistance exercise provokes an acute rise in circulating growth hormone (GH), and that this rise is severely blunted in older men and women. To determine whether this impairment simply reflects the decreased physical fitness of older people, we studied the effects of long-term resistance training on circulating levels of GH and insulin-like growth factor I (IGF-I) and on the acute GH response to exercise in 5 men and 9 women, aged 69.6 +/- 1.1 yrs (SEM). Subjects were randomly assigned to either an exercise program, consisting of 12 weight-lifting exercises (3 sets of 8 repetitions, 3 times each week) or to a control group. After testing maximum baseline strength by the 1 RM method, subjects returned to the laboratory for assessment of basal GH and IGF-I levels and the GH response to exercise. Venous blood was drawn at baseline, after each of 12 exercises (3 sets of 8 repetitions at 85% 1 RM), and every 2 minutes into the first 10 minutes of recovery. The exercise circuit with blood sampling was repeated at 15, 30 and 52 weeks for both groups. Basal GH and IGF-I values did not change in either group throughout the training period nor did the GH secretory response to exercise. Three exercisers had a peak GH concentration greater than 8 micrograms/l after 30 weeks of training, although only one of these showed a significant increase (29 micrograms/l) after 52 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscle strength and fiber adaptations to a year-long resistance training program in elderly men and women.

BACKGROUND: To study the effects of resistance training on muscle strength and size in older people, we enrolled 8 men and 17 women (mean age 68.2 +/- 1 SEM) into a one-year exercise trial. METHODS: Subjects were randomly assigned to exercise or control groups. Muscle biopsies were obtained from 11 subjects (8 exercisers/3 controls) at baseline and after 15 weeks; exercisers underwent another biopsy at 30 weeks. After testing maximum strength using the 1-RM method, the exercisers began a 12-exercise circuit (3 sets of 8 repetitions at 75% of 1-RM), 3 times a week. The controls repeated the strength testing every 15 weeks. They were asked to continue usual activities and not to start any exercise program. RESULTS: With exercise, muscle strength increased, average increases ranging from 30% (hip extensors) to 97% (hip flexors). Strength increased rapidly over 3 months, then plateaued for the duration of the experiment. No strength changes were observed in sedentary controls. Cross-sectional area of type 1 muscle fibers increased in exercisers by 15 weeks (29.4 +/- 1%, p < .02) and after 30 weeks (58.5 +/- 13.7%, p < .002) compared to baseline. Type 2 fiber area did not change at 15 weeks, but increased by 30 weeks of training (66.6 +/- 9.5%, p < .0002). CONCLUSIONS: These results suggest that prolonged moderate to high intensity resistance training may be carried out by healthy older adults with reasonable compliance, and that such training leads to sustained increases in muscle strength. These improvements are rapidly achieved and are accompanied by hypertrophy of both type 1 and type 2 muscle fibers.

Age-dependent effect of resistance exercise on growth hormone secretion in people.

We measured serum GH responses to a standardized circuit of resistance exercise in 12 young subjects (6 men and 6 women; 27 +/- 1.6 yr old) and in 11 elders (6 men and 5 women; 72 +/- 0.8 yr old). Initial assessment of strength [1 repetition maximum (1RM)] was made of 12 muscle groups using Nautilus equipment. One week later, subjects carried out the exercise protocol, 3 sets of 8 repetitions for each of the 12 exercises, at 70% of predetermined 1RM values. Venous blood was drawn at baseline, after each exercise, and every 2 min during 10 min of recovery. In young subjects serum immunoreactive GH rose by completion of the second exercise, increased and remained elevated through the remainder of the exercise period, and decreased toward baseline by 10 min of recovery. In the elderly subjects, baseline GH values were similar to those in the young (1.76 +/- 0.41 vs. 2.61 +/- 0.73 micrograms/L) and did not increase above 6 micrograms/L at any time during or after exercise. Exercise increased GH in both groups, but peak values (14.9 +/- 3.5 micrograms/L in young; 2.44 +/- 0.6 micrograms/L in old) and integrated (198 +/- 47 in young; 37.8 +/- 0.8 in old) were significantly greater in the young subjects (P less than 0.05). GH responses showed no gender difference in either group. Brief increases in pulse rate were observed during individual exercises, but sustained elevations did not occur. To assess the effect of exercise intensity on GH response, we compared responses to exercise at 70% and 85% of 1RM in 7 young and 11 older people. In the young subjects, GH responses were nonsignificant at 60% and increased progressively at 70% and 85% of 1RM. No significant effect of exercise intensity was observed in the older subjects. We conclude that resistance exercise promptly elevates circulating GH concentrations in healthy young adults. This response is related to the intensity of the resistance stimulus, although a small contribution of aerobic stress cannot be excluded. The GH response to resistance activity is grossly diminished in healthy elderly men and women.

Muscle hypertrophy response to resistance training in older women.

We conducted a 12-wk resistance training program in elderly women [mean age 69 +/- 1.0 (SE) yr] to determine whether increases in muscle strength are associated with changes in cross-sectional fiber area of the vastus lateralis muscle. Twenty-seven healthy women were randomly assigned to either a control or exercise group. The program was satisfactorily completed and adequate biopsy material obtained from 6 controls and 13 exercisers. After initial testing of baseline maximal strength, exercisers began a training regimen consisting of seven exercises that stressed primary muscle groups of the lower extremities. No active intervention was prescribed for the controls. Increases in muscle strength of the exercising subjects were significant compared with baseline values (28-115%) in all muscle groups. No significant strength changes were observed in the controls. Cross-sectional area of type II muscle fibers significantly increased in the exercisers (20.1 +/- 6.8%, P = 0.02) compared with baseline. In contrast, no significant change in type II fiber area was observed in the controls. No significant changes in type I fiber area were found in either group. We conclude that a program of resistance exercise can be safely carried out by elderly women, such a program significantly increases muscle strength, and such gains are due, at least in part, to muscle hypertrophy.

Relationship of body composition, muscle strength, and aerobic capacity to bone mineral density in older men and women.

We evaluated the relationship of body composition, maximal aerobic capacity (VO2max), and muscle strength to bone mineral density in 91 healthy men and women, age 61-84 years. Lean body mass was estimated from two independent measures of fat mass, bioelectrical impedance and skinfold thickness. VO2max was determined by treadmill ergometry with direct measurement of oxygen consumption. Grip and back strength were measured by isometric dynamometry. Mineral density of lumbar spine and midradius were measured by dual- and single-photon absorptiometry. Men had significantly greater lean mass, muscle strength, aerobic capacity, and bone density than women. In women, grip strength correlated with forearm and spine density (r = 0.37, r = 0.28, p less than 0.05). In men, grip strength correlated with forearm density (r = 0.47, p less than 0.05), and back strength was significantly correlated with both spine (r = 0.46, p less than 0.01) and forearm density (r = 0.46, p less than 0.01). In women, neither forearm nor spine density correlated significantly with aerobic capacity. In men, midradius density did not correlate significantly with oxygen consumption, but the simple correlation between spine density and VO2max was significant (r = 0.41, p less than 0.05). Back strength and VO2max were significantly related in men (r = 0.47, p less than 0.01). By stepwise multiple regression, back strength emerged as the most robust predictor of spine mineral, accounting for 19% of the variation in bone density. Addition of VO2max to the regression did not add significant predictive value. However, when VO2max was expressed per kilogram lean body mass, both back strength and VO2max contributed significantly to the prediction of spine density in men, and the coefficient of determination R2 increased to 0.30. We conclude that body mass and grip strength, but not aerobic capacity, significantly predict bone density in elderly women. In elderly men, back strength is a more robust predictor of axial bone density than traditional expressions of aerobic capacity, but VO2max per kilogram lean mass and back strength both make significant contributions to the prediction of spine mineral density. The applicability of these results to younger men and women is uncertain.

Inhibition of plasma vasopressin after drinking in dehydrated humans.

To study the effects of nonosmotic and nonvolumetric factors that may influence secretion of vasopressin, serum Na+, K+, and osmolality (Osm), hemoglobin, hematocrit, plasma arginine vasopressin (AVP), aldosterone (PA), and renin activity (PRA) were measured in five men and three women (26-50 yr, 73 +/- 4 kg) before and after 24 h of mild dehydration (food but no fluid) and seven times during the 1st h after rehydration with 10 ml/kg of tap water (17.5 +/- 0.5 degrees C) consumed in 105 s (range 35-240 s). Dehydration increased mean serum Na+ 3.7 +/- 0.7 meq/l (P less than 0.05), osmolality 9.1 +/- 1.1 mosmol/kg (P less than 0.05), and AVP from a hydrated level of 1.7 +/- 0.2 to 3.3 +/- 0.5 pg/ml (delta = 1.6 pg/ml, P less than 0.05). After rehydration AVP fell to 2.4 +/- 0.3 pg/ml (P less than 0.05) within 3 min and reached the water-replete level of 1.8 +/- 0.3 pg/ml 9 min after drinking started. Serum Na+ and Osm did not change until 30-60 min after drinking. No significant changes occurred in PRA, hemogloblin, hematocrit, or calculated delta in plasma volume, but PA increased from 11.1 +/- 1.5 ng/dl after dehydration to 15.6 +/- 2.6 ng/dl (P less than 0.05) between 30 and 60 min after drinking. The rapid fall in plasma AVP after rehydration took place in the absence of the expected changes in the primary regulators of plasma AVP (i.e., osmolality and plasma volume), with no change in blood pressure. The results suggest that oropharyngeal factors, alone or combined with gastric stimuli, are implicated.