Influence of a brisk walking program on postural responses in sedentary older women: a randomised trial

This study analyzes the evolution in kinematic and non-linear stabilometric parameters in elderly sedentary women selected to participate in a brisk walking program. Ninety-four women were randomly selected for a program of 78 sessions over 6 months, with three sessions of 60 min per week. On the force platform, participants were assessed with both eyes opened as well as eyes closed during a period of 51.2 s and the sampling frequency was 40 Hz. The main dependent kinematic variables were the length, stabilogram surface, and the mean position in anteroposterior as well as medio-lateral directions. For the dynamic approach, we have selected the parameters of recurrence quantification analysis, sample entropy, and multiscale entropy. The kinematic and the time series analysis of group × time interactions demonstrated that 6 months of walk-training lacked influence on kinematic postural responses and on dynamical measurements. The weekly brisk walking program was situated on flat ground and consisted of three 60-min weekly sessions lasting 6 months, leading to no significant effect on postural responses. In regards to international recommendations brisk walking is a pertinent exercise. However, in older sedentary women, our study indicated a systemic lack of influence of 6 months' walk-training on flat ground on kinematic postural responses and on dynamical measures obtained by time series analysis.

Effect of a 6-Month Brisk Walking Program on Walking Endurance in Sedentary and Physically Deconditioned Women Aged 60 or Older: A Randomized Trial

BACKGROUND

Walking endurance is a predictor of healthy ageing.

OBJECTIVE

To examine if a 6-month brisk walking program can increase walking endurance in sedentary and physically deconditioned older women.

TRIAL DESIGN

Randomized controlled trial.

SETTING

Women recruited from public meetings aimed at promoting physical activity in women aged 60 or older.

SUBJECTS

121 women aged 65.7 ± 4.3 years, with sedentary lifestyle (Physical Activity Questionnaire for the Elderly score < 9.4), and a 6-minute walking distance (6MWD) below normal value based on their gender, age, and body weight, and weight.

METHODS

Women were randomly assigned to a 150 min/week brisk walking program (two supervised sessions and one session on their own per week) for six months (exercisers) (n=61) or a control group with physical activity allowed freely (n=60).

OUTCOME

The primary outcome was relative change in 6MWD.

RESULTS

54/61 exercisers and 55/60 control subjects completed the program and data analysis was possible for 51 exercisers and 47 controls. At baseline, 6MWD was on average 23.1% and 22.5% below age-matched norms in exercisers and controls, respectively. Attendance rate for supervised sessions was 92% in exercisers. The 6MWD increased more significantly in exercisers than in controls (mean increase of 41.5% vs 11.0 %; p<0.0001). Over the 6-month program, 38 exercisers (74.5%) vs 5 controls (10.6%) had a 6MWD over the age-matched norm (p<0.0001). Exercisers with the highest tertile of 6MWD improvement (>46%) were those with baseline lowest values of 6MWD (p=0.001) and highest values of body mass index (BMI) (p<0.01).

CONCLUSION

Present results support recommendation that brisk walking programs should be encouraged to improve walking endurance in physically deconditioned women aged 60 or older, especially in those with high BMI.

Building Bridges for Innovation in Ageing: Synergies between Action Groups of the EIP on AHA

The Strategic Implementation Plan of the European Innovation Partnership on Active and Healthy Ageing (EIP on AHA) proposed six Action Groups. After almost three years of activity, many achievements have been obtained through commitments or collaborative work of the Action Groups. However, they have often worked in silos and, consequently, synergies between Action Groups have been proposed to strengthen the triple win of the EIP on AHA. The paper presents the methodology and current status of the Task Force on EIP on AHA synergies. Synergies are in line with the Action Groups' new Renovated Action Plan (2016-2018) to ensure that their future objectives are coherent and fully connected. The outcomes and impact of synergies are using the Monitoring and Assessment Framework for the EIP on AHA (MAFEIP). Eight proposals for synergies have been approved by the Task Force: Five cross-cutting synergies which can be used for all current and future synergies as they consider overarching domains (appropriate polypharmacy, citizen empowerment, teaching and coaching on AHA, deployment of synergies to EU regions, Responsible Research and Innovation), and three cross-cutting synergies focussing on current Action Group activities (falls, frailty, integrated care and chronic respiratory diseases).

Influence of a brisk walking program on isokinetic muscular capacities of knee in sedentary older women

This study analyzed the evolution in peak torque (PT) and mean power (MP) isokinetic parameters in the quadriceps and hamstring muscles of elderly sedentary women who were randomly selected to participate in a brisk walking program for 6 months. The 121 sedentary women of this study presented a mean score of 5.3 (±1.7) on the Physical Activity Questionnaire for the Elderly and covered 86 % of the theoretical distance on the 6-min walk test. The isokinetic evaluation was performed on both sides at 60°/s and 180°/s. PT and MP were selected for analysis. Women in the trained group (n = 61) participated in a program of 78 sessions over 6 months with three sets of 60 min of exercise per week. For this group, heart rate, time and distance were, respectively, 125.2 bt/min (±10), 37.9 min (±4.2) and 3756.3 m (±445.4). The analysis of the group × time interaction demonstrated an increase in the PT of the dominant-side hamstrings (p < 0.001). In the trained group, we observed a significant increase in PT at 60°/s for the hamstrings on both sides (0.01 < p < 0.02) and a significant increase in MP for the hamstrings at 60°/s on the nondominant side (p < 0.05). The study indicates a minor, though significant, influence of a brisk walking program on the peak torque and mean power of the quadriceps and hamstring muscles in sedentary women over 60 years.

[Intensive training and menstrual disorders in young female: Impact on bone mass]

Participation in recreational physical activity is widely acknowledged to provide significant health benefits. Conversely, intense training imposes several constraints, such as intermittent or chronic metabolic and psychogenic training stressors and maintenance of very low body fat to maximize performance. Adolescent and adult athletic women are therefore at risk of overtraining and/or poor dietary intake, which may have several consequences for endocrine function particularly on hypothalamic-pituitary-gonadal axis. Female athletes, particularly those participating in sports needing leanness or low body weight, present a high prevalence of menstrual disorders with clinical manifestations ranging from delayed menarche, oligomenorrhea to primary and secondary amenorrhea. A high degree of variability according to the type of sport and the intensity of the practice is however observed. Exercise-related reproductive dysfunction may have some consequences for growth velocity and peak bone mass acquisition during adolescence and bone pathologies in adults. Recent findings highlight the endocrine role of adipose tissue and energy balance in the regulation of homeostasis and reproductive function. A better understanding of the mechanisms whereby intense training affects the endocrine systems may orient research to develop innovative strategies probably based on individualized nutritional approach to improve the medical care of these female athletes and protect their reproductive function.

Congenital taurine deficiency in mice is associated with reduced sensitivity to nociceptive chemical stimulation

The amino acid taurine is required for development and functioning of the central and peripheral nervous system where it exerts osmoregulatory, neuromodulatory and anti-apoptotic actions. It is subject to cellular import by the taurine transporter slc6a6. Absence of the transporter and consequently, absence of taurine leads to several neurologic deficits and sensory losses. In a slc6a6 knock-out mouse model, consequences of congenital taurine deficiency were assessed in nociceptive sensory processes. The formalin assay, hot plate assay, and summated generator potentials in response to local nociceptive stimulation with gaseous CO2 were applied. Reduced responsiveness of slc6a6(-/-) mice to nociceptive stimulation was observed in particular to chemical nociceptive stimuli. Scl6a6 knock-out mice spent significantly less time licking the formalin injected paw and displayed smaller amplitudes of the nociceptive nasal mucosa potentials than wild-type mice (p=0.002 and 0.01 respectively). In contrast, withdrawal latencies on a hot plate did not significantly differ, suggesting that intracellular taurine deficits lead in particular to a hyposensitivity of nociceptive sensory neurons sensitive to noxious chemical stimulation. As hereditary absence of taurine affects biological processes of anatomical structure development, the altered nociceptive responses likely reflect consequences of compromised peripheral nervous system development.

Dexamethasone modulates expression of genes involved in the innate immune system, growth and stress and increases susceptibility to bacterial disease in Senegalese sole (Solea senegalensis Kaup, 1858)

Cortisol, the main glucocorticoid in fish, undertakes pleiotropic biological effects in response to stressors to maintain homeostasis. It can exert several actions on the immune system, growth and cellular metabolism, establishing a fine-tune regulation stress response and cross-talk interactions with other regulatory pathways. In this study, we investigated a causal relationship between high levels of glucocorticoids and susceptibility to pathogens and modification of gene expression profiles in Senegalese sole. For this purpose, we carried out two experiments using post-metamorphic individuals (21 days after hatching) that were exposed to dexamethasone (DXM), a potent glucocorticoid, in order to mimic cortisol effects. We quantified transcript levels of a wide set of genes involved in innate immune system (g-type lysozyme and hepcidin (hamp1)), HPI axis (crf, crfbp, pomcα, pomcβ, gr1 and gr2), HPT axis (tgb), cellular stress defense system (hsp70 and hsp90aa), GH/IGF axis (igf-I and igf-Ir) and the neuropeptide trh. Short-term exposure to 0.1, 1 and 10 ppm DXM provoked a reduction of pomcβ transcripts and an increase of crfbp mRNAs in a dose-dependent manner at 48 and 72 h after treatment. Moreover, g-type lysozyme transcript levels decreased significantly at 72 h whereas hamp1 mRNA levels increased at 48 h after exposure. Long-term DXM treatment (10 ppm DXM) affected negatively weight of soles (~20% lower than controls). Moreover, reduced mRNA levels were observed for pomcβ after 1 week and igf-I and hamp1 after 2 weeks. In contrast, crfbp and crf increased mRNA levels after 2 weeks. hsp70 exhibited a dual response increasing transcript levels at 1 week after treatment and reducing thereafter. No significant changes in gene expression were observed at any time during this study for tgb, trh, hsp90aa, pomcα, gr1 and gr2. Finally, a challenge experiment using the pathogen Photobacterium damselae subsp piscicida confirmed earlier and higher mortalities in DXM-treated animals. Taken together, these data indicate that a prolonged exposure to DXM increases the susceptibility to pathogens and reduces growth. Moreover, DXM can trigger a wide cellular response modulating the expression of genes involved in the innate immune system, HPI and GH/IGF axes as well as cellular stress defense. These results are highly valuable to evaluate responses associated to aquaculture stressful conditions and discriminate specific glucocorticoid-mediated effects.

In peripubertal girls, artistic gymnastics improves areal bone mineral density and femoral bone geometry without affecting serum OPG/RANKL levels

Peripubertal artistic gymnasts display elevated areal bone mineral density at various bone sites, despite delayed menarche and a high frequency of menstrual disorders, factors that may compromise bone health. The concomitant improvement in femoral bone geometry and strength suggested that this type of physical activity might have favourable clinical impact.

INTRODUCTION

The purpose of this study is to evaluate the effect of artistic gymnastics (GYM) on areal bone mineral density (aBMD), femoral bone geometry and bone markers and its relationship with the osteoprotegerin (OPG)/rank-ligand (RANKL) system in peripubertal girls.

METHODS

Forty-six girls (age 10-17.2 years) were recruited for this study: 23 elite athletes in the GYM group (training 12-30 h/week, age at start of training 5.3 years) and 23 age-matched (± 6 months; leisure physical activity ≤ 3 h/week) controls (CON). The aBMD at whole body, total proximal femur, lumbar spine, mid-radius and skull was determined using dual-X-ray absorptiometry. Hip structural analysis (HSA software) was applied at the femur to evaluate cross-sectional area (CSA, cm(2)), cross-sectional moment of inertia (CSMI, cm(4)), and the section modulus (Z, cm(3)) and buckling ratio at neck, intertrochanteric region and shaft. Markers of bone turnover and OPG/RANKL levels were also analysed.

RESULTS

GYM had higher (5.5-16.4%) non-adjusted aBMD and adjusted aBMD for age, fat-free soft tissue and fat mass at all bone sites, skull excepted and the difference increased with age. In the three femoral regions adjusted for body weight and height, CSA (12.5-18%), CSMI (14-18%), Z (15.5-18.6%) and mean cortical thickness (13.6-21%) were higher in GYM than CON, while the buckling ratio (21-27.1%) was lower. Bone markers decreased with age in both groups and GYM presented higher values than CON only in the postmenarchal period. A similar increase in RANKL with age without OPG variation was observed for both groups.

CONCLUSION

GYM is associated not only with an increase in aBMD but also an improvement in bone geometry associated with an increase in bone remodelling. These adaptations seem to be independent of the OPG/RANKL system.

Basal plasma leptin levels in healthy elderly males are related to physical fitness without impact on bone metabolism

AIM

Investigated the relationship between leptin levels or bone remodelling and physical fitness level in healthy elderly participants.

METHODS

Twenty women and 18 men (mean age 72.7 years, range 59-90) performed a maximal incremental exercise test to evaluate their maximal oxygen uptake (VOmax). Basal blood concentrations of bone biochemical markers (BM) and leptin were analysed.

RESULTS

Women presented higher values of leptin than men (+34.7%, P=0.024), but no difference related to gender was observed for the other biological parameters. Leptin levels were positively correlated with Body Mass Index (BMI) in both genders. Whether adjusted or not for BMI, leptin was negatively correlated with VOmax only in men (r=-0.55, P=0.02 and r=-0.57, P=0.01, respectively). No relationship between VOmax or leptin and BM was observed, except for leptin and osteocalcin in men (r=-0.66, P=0.015).

CONCLUSION

Our data suggest that neither physical fitness nor leptin level seems to have a noticeable effect in the regulation of bone cell activity in healthy elderly participants. In this specific population, physical fitness plays a crucial role on leptin secretion, independently of BMI variation, and this action appears to be sex-dependent.

Response of calciotropic hormones and bone turnover to brisk walking according to age and fitness level

Ageing is associated with a gradual bone loss and physical activity has been suggested as practical strategy for a non-pharmacological prevention of osteoporosis. However, until now, the specific mechanism by which physical activity affects bone tissue is not thoroughly understood. The aim of this study was to evaluate the effect of strenuous exercise on bone metabolism as a function of age and fitness level. Eighteen physically highly active elderly participants (mean age 71.7+/-7.3 years, HAcEl group), 18 moderately active elderly participants (mean age 71.9+/-8.6 years, ModEl group) and 9 young physically active participants (mean age 25.8+/-2.3 years, AcYo) participated in this study. Concentrations of plasma ionised calcium (iCa), serum parathyroid hormone (iPTH), 25-hydroxy-vitamin D [25(OH)D], and 1,25-dihydroxy-vitamin D3 [1,25(OH)(2)D3] as well as the bone biochemical markers type-I collagen C-telopeptide (CTX) for bone resorption and osteocalcin (OC) and bone alkaline phosphatase (B-ALP) for bone formation, were analyzed before and after a maximal incremental exercise test. In all groups, iCa decreased significantly (p<0.05 for ModEl and AcYo and p<0.001 for HAcEl) while iPTH increased significantly (p<0.01 for ModEl and HAcEl and p<0.001 for AcYo) after exercise. The levels of 1,25(OH)(2)D3, OC and CTX remained unchanged, while 25(OH)D decreased only in HAcEl group while B-ALP increased in ModEl group. In conclusion, strenuous exercise disturbed calcium homeostasis, mainly the iCa/iPTH equilibrium independently of gender, age or fitness level of the participants while no immediate effect on bone turnover was observed.

Asthma and exercise-induced bronchoconstriction in amateur endurance-trained athletes

High-level endurance training contributes to the development of asthma and exercise-induced bronchoconstriction but the effect of moderate endurance training on airway function remains to be determined. The aim of this study was to evaluate the prevalence of physician-diagnosed asthma and/or exercise-induced bronchoconstriction in moderately endurance-trained athletes. Ninety-five Mediterranean amateur endurance-trained athletes filled out a questionnaire about respiratory disorders and underwent a resting spirometry. Mean training volume was 10 h per week. The prevalence of asthma was found to be 4.2 %. All the athletes with asthma plus another one (5.3 %) reported having exercise-induced bronchoconstriction. These percentages are in the same range as those from the general population and much lower than those observed in elite endurance athletes. In contrast to elite athletes, our amateur endurance-trained athletes seem not exposed to a higher risk of asthma or exercise-induced bronchoconstriction than the general population. We suggest that 10 h per week of moderate endurance training in a temperate climate area does not lead to respiratory disease.

Competitive Season of Triathlon Does not Alter Bone Metabolism and Bone Mineral Status in Male Triathletes

This longitudinal study evaluated the effects of a triathlon season on bone metabolism and hormonal status. Seven male competitive triathletes (mean age 19.3 years, range 18 - 20) with 5.0 +/- 0.3 years of competition experience were tested twice during the season: at the beginning of training and 32 weeks later. Total and regional bone mineral density (BMD) was determined by dual-energy X-ray absorptiometry, while bone turnover was evaluated by specific biochemical markers: bone-specific alkaline phosphatase (B-ALP), osteocalcin, and urinary type I collagen C-telopeptide. In addition, sexual, calciotropic and somatotropic hormones were also analyzed. After 32 weeks, a BMD increase was found at the lumbar spine (1.9 %; p = 0.031) and skull (3.1 %; p = 0.048), while no variation was observed for total body or at the proximal femur. The B-ALP level decreased (-23.2 %; p = 0.031), but no variation was found for the other bone markers. 1.25 (OH) (2)D3, IGF-1 and the bioavailability IGF-1 index (IGF-1/IGFBP-3) increased by 18.3 % (p = 0.047), 29 % (p = 0.048), 33 % (p = 0.011), respectively, while PTH, testosterone, IGFBP-3 and cortisol concentrations were unchanged. In conclusion, the triathlon season had a moderately favourable effect on BMD, although a slowing down of bone formation activity was observed. No variation in hormonal levels was observed that could have limited the effects of exercise on bone tissue.

Caffeine or melatonin effects on sleep and sleepiness after rapid eastward transmeridian travel

We measured the effects of slow-release caffeine (SRC) and melatonin (Mlt) on sleep and daytime sleepiness after a seven-time zone eastbound flight. In a double-blind, randomized, placebo-controlled study, each of three groups of nine subjects was given either 300 mg SRC on recovery day 1 (D1) to D5 (0800) or 5 mg Mlt on preflight D-1 (1700), flight day D0 (1600), and from D1 to D3 (2300), or placebo (Pbo) at the same times. Nighttime sleep was evaluated by polysomnography and daytime sleepiness from measurements of sleep latencies and continuous wrist actigraphy. Compared with baseline, we found a significant rebound of slow-wave sleep on night 1 (N1) to N2 under Pbo and Mlt and a significant decrease in rapid eye movement sleep on N1 (Pbo) and N1-N3 (Mlt). Sleepiness was objectively increased under Pbo (D1-D6) and Mlt (D1-D3). SRC reduced sleepiness but also tended to affect sleep quality until the last drug day. In conclusion, both drugs have positive effects on some jet lag symptoms after an eastbound flight: SRC on daytime sleepiness, and Mlt on sleep.

Maximal oxygen uptake and power of lower limbs during a competitive season in triathletes

BACKGROUND

In order to study the effect of a competitive triathlon season on maximal oxygen uptake (VO2max), aerobic power (AeP) and anaerobic performance (AnP) of the lower limbs, eight triathletes performed exercise tests after: (1) a pre-competition period (Pre-COMP) (2) a competitive period (COMP), and (3) a low (volume and intensity) training period (Post-COMP). The tests were a vertical jump-and-reach test and an incremental exercise test on a cycle ergometer. Ventilatory data were collected every minute during the incremental test with an automated breath-by-breath system and the heart-rate was monitored using a telemetric system.

RESULTS

No changes in VO2max were observed, whereas AeP decreased after Post-COMP compared to Pre-COMP and COMP and AnP decreased during COMP compared to Pre-COMP and Post-COMP. In addition, second ventilatory threshold (VT2) and power output at first ventilatory threshold (VT1) and VT2 decreased after Post-COMP.

CONCLUSION

This study showed that six weeks of low volume and intensity of training is too long a period to preserve adaptations to training, although a stable maximal oxygen uptake throughout the triathlon season was observed. Moreover, the AnP decrease during COMP was probably in relation with the repetitive nature of the training mode and/or triathlon competitions.

Carbohydrate dependence during hard-intensity exercise in trained cyclists in the competitive season: importance of training status

To test the hypothesis that intensive endurance training increases CHO utilisation during hard-intensity exercise, seven competitive road cyclists (Cy) performed three 50-min steady-state exercise tests on a cycle ergometer above their ventilatory threshold (+ 15 %) over the course of a cycling season (January [ET1], May [ET2] and September [ET3]). We compared the data with the baseline values of seven sedentary controls (Sed). CHO oxidation in Cy was higher in ET2 and ET3 than in ET1 (p < 0.05), was lower in ET3 than in ET2 (p < 0.05) and was higher in Cy than in Sed only in ET2 (p < 0.05). Lactate kinematics were lower in Cy than in Sed in all conditions (p < 0.05), but in Cy they were lower in ET2 than in ET1 and higher in ET3 than in ET2 (p < 0.05). Race performance was impaired and the overtraining score was increased at ET3 in comparison with ET2 (p < 0.05). We conclude that competitive cyclists increase CHO oxidation during hard-intensity exercise over the course of a season, but show a decline by the end of the season in association with the appearance of an overtraining state. Thus, well-trained cyclists develop a CHO dependence, which is modified with training status.

Slow release caffeine and prolonged (64-h) continuous wakefulness: effects on vigilance and cognitive performance

Some long work or shift work schedules necessitate an elevated and prolonged level of vigilance and performance but often result in sleep deprivation (SD), fatigue and sleepiness, which may impair efficiency. This study investigated the effects of a slow-release caffeine [(SRC) at the daily dose of 600 mg] on vigilance and cognitive performance during a 64 h continuous wakefulness period. Sixteen healthy males volunteered for this double-blind, randomised, placebo controlled, two-way crossover study. A total of 300-mg SRC or placebo (PBO) was given twice a day at 21:00 and 9:00 h during the SD period. Vigilance was objectively assessed with continuous electroencephalogram (EEG), the multiple sleep latency tests (MSLT) and wrist actigraphy. Cognitive functions (information processing and working memory), selective and divided attention were determined with computerised tests from the AGARD-NATO STRES Battery (Standardised Tests for Research with Environmental Stressors). Attention was also assessed with a symbol cancellation task and a Stroop's test; alertness was appreciated from visual analogue scales (VAS). Tests were performed at the hypo (02:00-04:00 h, 14:00-16:00 h) and hypervigilance (10:00-12:00 h, 22:00-00:00 h) periods during SD. Central temperature was continuously measured and safety of treatment was assessed from repeated clinical examinations. Compared with PBO, MSLT showed that SRC subjects were more vigilant from the onset (P=0.001) to the end of SD (P < 0.0001) whereas some cognitive functions were improved till the thirty third of SD but others were ameliorated through all the SD period and alertness was better from the thirteenth hour of SD, as shown by Stroop's test (P=0.048). We showed that 300-mg SRC given twice daily during a 64-h SD is able to antagonize the impairment produced on vigilance and cognitive functions.

Resynchronization of hormonal rhythms after an eastbound flight in humans: effects of slow-release caffeine and melatonin

The aim of this work was to investigate the potential chronobiotic properties of slow-release caffeine, in comparison with melatonin, on resynchronization of endogenous melatonin and cortisol secretions after an eastbound flight by jet incurring a time loss of 7 h. A group of 27 reservists of the US Air Force received either slow-release caffeine (300 mg), melatonin (5 mg) or placebo before, during and/or after the transmeridian flight. Saliva and urine were sampled before the flight in the United States (from day -2 to day 0) and after the flight in France (from day 1 to day 10). Saliva was collected once a day on waking to determine saliva melatonin and cortisol concentrations. In addition, concentrations of caffeine in saliva were determined three times a day and of 6-sulphatoxymelatonin in urine collected overnight to check that the treatment regimes had been complied with. From day 3 to day 5, post-flight saliva melatonin concentrations were significantly different from control values in the placebo group only. During treatment with melatonin, the mean urinary 6-sulphatoxymelatonin concentration in the melatonin group was more than twice as high as in the two other groups. In the slow-release caffeine group and the melatonin group, mean saliva cortisol concentrations were significantly lower than control from day 2 to day 5, whereas the placebo group had a mean saliva cortisol concentration significantly lower than the control value from day 2 to day 9. In conclusion, these results indicate that administration of slow-release caffeine, as well as of melatonin, allows a faster resynchronization of hormone rhythms during the 4 days following an eastbound flight incurring the loss of 7 h.

Suppressed injury-induced rise in spinal prostaglandin E2 production and reduced early thermal hyperalgesia in iNOS-deficient mice

It is widely accepted that peripheral injury increases spinal inducible cyclooxygenase (COX-2) expression and prostaglandin E(2) (PGE(2)) formation as key mediators of nociceptive sensitization. Here, we used inducible nitric oxide synthase (iNOS) gene-deficient (iNOS-/-) mice to determine the contribution of iNOS-derived nitric oxide (NO) to this process. iNOS-/- mice exhibited reduced thermal hyperalgesia after zymosan injection. Spinal NO and PGE(2) formation both remained at baseline levels, in contrast to wild-type (wt) mice. In wt mice reduced hyperalgesia similar to that seen in iNOS-/- mice was induced by local spinal, but not by systemic treatment with the iNOS inhibitor l-NIL, suggesting that the reduced heat sensitization in iNOS-/- mice was attributable to the lack of spinal rather than peripheral iNOS. Two additional observations indicate that the antinociceptive effects of iNOS inhibition are dependent on a loss of stimulation of PG synthesis. First, intrathecal injection of the COX inhibitor indomethacin, which exerted pronounced antinociceptive effects in wt mice, was completely ineffective in iNOS-/- mice. Second, treatment with the NO donor RE-2047 not only completely restored spinal PG production and thermal sensitization in iNOS-/- mice but also its sensitivity to indomethacin. In both types of mice induction of thermal hyperalgesia was accompanied by similar increases in COX-1 and COX-2 mRNA expression. The stimulation of PG production by NO therefore involves an increase in enzymatic activity, rather than an alteration of COX gene expression. These results indicate that NO derived from spinal iNOS acts as a fast inductor of spinal thermal hyperalgesia.

Inhibition of noxious stimulus-induced spinal prostaglandin E2 release by flurbiprofen enantiomers: a microdialysis study

Peripheral noxious stimuli have been shown to induce prostaglandin (PG) E2 release at the site of inflammation and in the spinal cord. The antiinflammatory and antinociceptive effects of cyclooxygenase-inhibiting drugs are thought to depend on the inhibition of PG synthesis. R-Flurbiprofen, however, does not inhibit cyclooxygenase activity in vitro but still produces antinociceptive effects. To find out whether R-flurbiprofen acts via inhibition of spinal PG release, concentrations of PGE2 and flurbiprofen in spinal cord tissue were assessed by microdialysis. The catheter was transversally implanted through the dorsal horns of the spinal cord at level L4. R- and S-flurbiprofen (9 and 27 mg kg(-1), respectively) were administered intravenously 10-15 min before subcutaneous injection of formalin into the dorsal surface of one hindpaw. Flurbiprofen was rapidly distributed into the spinal cord with maximal concentrations after 30-45 min. Baseline PGE2 dialysate concentrations were 100.6 +/- 6.4 pg ml(-1) (mean +/- SEM). After formalin injection they rose about threefold with a maximum of 299.4 +/- 68.4 pg ml(-1) at 7.5 min. After approximately 1 h PGE2 levels returned to baseline. Both flurbiprofen enantiomers completely prevented the formalin-induced increase of spinal PGE2 release and reduced PGE2 concentrations below basal levels. S- and R-flurbiprofen at 9 mg kg(-1) produced a minimum of 15.8 +/- 5.2 and 27.7 +/- 14.9 pg ml(-1), respectively, and 27 mg kg(-1) S- and R-flurbiprofen resulted in 11.7 +/- 1.7 and 9.3 +/- 4.7 pg ml(-1), respectively. PGE2 levels remained at the minimum up to the end of the observation period at 5 h. When 27 mg kg(-1) R-flurbiprofen was injected intravenously without subsequent formalin challenge, baseline immunoreactive PGE2 concentrations were not affected. S-Flurbiprofen (27 mg kg(-1)), however, led to a moderate reduction (approximately 40%). The data suggest that antinociception produced by R-flurbiprofen is mediated at least in part by inhibition of stimulated spinal PGE2 release and support the current view that increased spinal PGE2 release significantly contributes to nociceptive processing.

How accurate is optical second-harmonic generation?

We have checked whether the frequency ratio between fundamental and second-harmonic optical frequencies is exactly 1:2 by measuring the frequency difference between the second harmonics of two diode lasers and comparing it with the frequency difference of the fundamentals. We have improved the 30-year-old experimental limit on the accuracy of the 1:2 frequency ratio by 7 orders of magnitude for frequency-dependent shifts to 2.3 parts in 10(13) for a KNbO(3) crystal.