Peak Running Velocity vs. Critical Speed: Which One Is Better to Prescribe Endurance Training to Recreational Runners?

ABSTRACT: Figueiredo, DH, Figueiredo, DH, Manoel, FA, and Machado, FA. Peak running velocity vs. critical speed: which one is better to prescribe endurance training to recreational runners? J Strength Cond Res 37(9): 1783-1788, 2023-This study aimed to evaluate the effects of 5 weeks of training prescribed by peak running velocity obtained on the track (Vpeak_TR) and their respective time limit (Tlim), as well as by critical speed (CS), on physiological and endurance performance parameters in recreational runners. Twenty-two male runners were distributed into a Vpeak_TR group (GVP) and CS group (GCS) with a predefined program, alternating moderate-intensity continuous training and high-intensity interval training. Maximum oxygen uptake (V̇O2max), and its respective velocity (vV̇O2max), Vpeak_TR, Tlim at 100% Vpeak_TR, 5-km running performance, CS, and D' (maximum distance covered above CS) were assessed at pretraining and posttraining period. There was a significant increase from pretraining to posttraining in Vpeak_TR (GVP = 4.5 ± 3.1% vs. GCS = 7.5 ± 4.2%), vV̇O2max (GVP = 3.9 ± 3.8% vs. GCS = 8.6 ± 6.7%), and mean velocity 5-km (GVP = 5.6 ± 3.3% vs. GCS = 7.3 ± 3.5%) and decrease in 5-km time (GVP = -5.1 ± 3.0% vs. GCS = -6.8 ± 3.0%). CS and V̇O2max significantly improved in GCS (9.3 ± 8.4% and 6.0 ± 6.8%, respectively), with no difference for GVP (2.8 ± 5.6% and 1.3 ± 8.4%, respectively). No differences were observed between groups for all variables. These findings give further supports to the notion that both variables obtained on the track are valid tools to prescribed training in recreational runners.

Comparison of theoretical approaches for epidemic processes with waning immunity in complex networks.

The role of waning immunity in basic epidemic models on networks has been undervalued while being noticeably fundamental for real epidemic outbreaks. One central question is which mean-field approach is more accurate in describing the epidemic dynamics. We tackled this problem considering the susceptible-infected-recovered-susceptible (SIRS) epidemic model on networks. Two pairwise mean-field theories, one based on recurrent dynamical message-passing (rDMP) theory and the other on the pair quenched mean-field (PQMF) theory, are compared with extensive stochastic simulations on large networks of different levels of heterogeneity. For waning immunity times longer than or comparable with the recovering time, rDMP outperforms PQMF theory on power-law networks with degree distribution P(k)∼k^{-γ}. In particular, for γ>3, the epidemic threshold observed in simulations is finite, in qualitative agreement with rDMP, while PQMF leads to an asymptotically null threshold. The critical epidemic prevalence for γ>3 is localized in a finite set of vertices in the case of the PQMF theory. In contrast, the localization happens in a subextensive fraction of the network in rDMP theory. Simulations, however, indicate that localization patterns of the actual epidemic lay between the two mean-field theories, and improved theoretical approaches are necessary to understanding the SIRS dynamics.

Dose-Response Relationship Between Internal Training Load and Changes in Performance During the Preseason in Youth Soccer Players.

ABSTRACT: Figueiredo, DH, Figueiredo, DH, Moreira, A, Gonçalves, HR, and Dourado, AC. Dose-response relationship between internal training load and changes in performance during the preseason in youth soccer players. J Strength Cond Res 35(8): 2294-2301, 2021-The aim of this study was to describe training intensity distribution based on the session rating of perceived exertion (sRPE) and heart rate (HR) methods and examine the dose-response relation between internal training load (ITL) and change in performance of 16 youth soccer players (mean ± SD age: 18.75 ± 0.68 years, height: 175.3 ± 5.5 cm, body mass: 68.7 ± 6.5 kg, and body fat: 10.7 ± 1.2%) belonging to a Brazilian first division team during a 3-week preseason. The sRPE and HR data were registered daily to calculate the ITL and the training intensity distribution, in 3 intensity zones (low, moderate, and high). The Yo-yo Intermittent Recovery Level 1 (Yo-yo IR1) was evaluated before and after experimental period. The total time spent in the low-intensity zone (HR method) was greater (p < 0.01) compared with the moderate- and high-intensity zones. No difference was observed between training intensity zones determined by the sRPE method (p > 0.05). Negative correlations were observed between weekly mean sRPE-TL (r = -0.69), Edward's-TL (r = -0.50), and change in Yo-yo IR1. Linear regression indicated that weekly mean sRPE-TL (F1;14 = 13.3; p < 0.01) and Edward's-TL (F1;14 = 4.8; p < 0.05) predicted 48.7 and 25.5% of the variance in performance change, respectively. Stepwise linear regression revealed that these 2-predictor variables (F2;13 = 18.9; p < 0.001) explained 74.5% of the variance in performance change. The results suggest that the sRPE and HR methods cannot be used interchangeably to determine training intensity distribution. Moreover, sRPE-TL seems to be more effective than the HR-based TL method to predict changes in performance in youth soccer players.

High prevalence regimes in the pair-quenched mean-field theory for the susceptible-infected-susceptible model on networks.

Reckoning of pairwise dynamical correlations significantly improves the accuracy of mean-field theories and plays an important role in the investigation of dynamical processes in complex networks. In this work, we perform a nonperturbative numerical analysis of the quenched mean-field theory (QMF) and the inclusion of dynamical correlations by means of the pair quenched mean-field (PQMF) theory for the susceptible-infected-susceptible model on synthetic and real networks. We show that the PQMF considerably outperforms the standard QMF theory on synthetic networks of distinct levels of heterogeneity and degree correlations, providing extremely accurate predictions when the system is not too close to the epidemic threshold, while the QMF theory deviates substantially from simulations for networks with a degree exponent γ>2.5. The scenario for real networks is more complicated, still with PQMF significantly outperforming the QMF theory. However, despite its high accuracy for most investigated networks, in a few cases PQMF deviations from simulations are not negligible. We found correlations between accuracy and average shortest path, while other basic network metrics seem to be uncorrelated with the theory accuracy. Our results show the viability of the PQMF theory to investigate the high-prevalence regimes of recurrent-state epidemic processes in networks, a regime of high applicability.

TAMOXIFEN-INDUCED CHORIORETINAL CHANGES: An Optical Coherence Tomography and Optical Coherence Tomography Angiography Study.

PURPOSE: To study structural chorioretinal changes in tamoxifen-treated patients. METHODS: Cross-sectional case-control study comparing structural chorioretinal aspects in tamoxifen-treated patients and healthy controls. Enhanced depth spectral domain optic coherence tomography with choroidal binarization and optic coherence tomography angiography were performed. Individual retinal layer thickness and chorioretinal vascular components were compared. Subgroup analysis regarding history of chemotherapy was performed. RESULTS: Two hundred eyes of 100 TAM-treated patients (Group 1) and 80 eyes of 40 healthy controls (Group 2) were included. Of the 200 spectral domain optic coherence tomography scans from patients, 2 showed structural changes attributable to tamoxifen. Group 1 showed significantly lower values in choroidal parameters and in total retinal, ganglion cell layer, inner plexiform layer, outer nuclear layer, and retinal pigment epithelial thicknesses as well as an increased thickness in the outer plexiform layer. The subgroup not submitted to chemotherapy maintained significant reductions in total retinal thickness, ganglion cell layer, retinal pigment epithelium, outer nuclear layer, outer retinal layer, choroidal parameters, as well as an increased thickness in the outer plexiform layer, in comparison with Group 2. CONCLUSION: Subclinical structural retinal changes could indicate early retinal pigment epithelial and photoreceptor damage. The new finding of choroidal thinning could point toward another important pathophysiologic process in tamoxifen-induced toxicity.

Características antropométricas e motoras em jogadores de futebol: diferenças entre categorias sub17. sub19 e profissional / Antrophometric and motor caratheristics in soccer players: differences between under 17. under 19 and professional categories

O objetivo do presente estudo foi analisar e comparar as características antropométricas e motoras de atletas pertencentes as categorias Sub17, Sub19 e Profissional. Todos os dados foram coletados anteriormente ao início da temporada competitiva. A amostra deste estudo foi composta por 48 futebolistas masculinos divididos em três grupos: Sub17 (n=16), Sub19 (n=16) e Profissional (n=16). Para avaliar as características antropométricas foram realizadas avaliações de estatura e de composição corporal por meio de Pletismografia por deslocamento de ar. Já para determinação das características motoras foram realizados os testes de resistência aeróbia (Yo-Yo IR1); Counter movement jump (CMJ); Squat jump (SJ); performance de sprint 5m e 30m e potência anaeróbia (RAST teste) para determinação das potências máxima, média e mínima. Para determinar as diferenças entre as categorias no que se refere as características antropométricas e motoras uma ANOVA one way complementando-se com o teste posthoc de Bonferroni foi utilizado, levando-se em consideração um nível de significância de p>0,016. Atletas profissionais apresentaram maiores valores de peso corporal e massa magra absoluta se comparadas as categorias Sub17 e Sub19, não sendo identificadas diferenças para massa gorda absoluta e relativa e massa magra relativa. Não foram identificadas diferenças antropométricas entre os atletas das categorias Sub17 e Sub19. Atletas profissionais apresentaram valores de CMJ, SJ, sprint de 30m e potência máxima, média e mínima maiores do que atletas Sub17 e Sub19, não apresentando diferença em relação ao Yo-Yo IR1 e sprint de 5m. Atletas Sub19 apresentaram maiores valores de Yo-Yo IR1 se comparados ao Sub17 e Profissionais e maiores valores de CMJ, sprint de 30m e potência média e mínima se comparado aos atletas Sub17. Atletas de diferentes categorias apresentam características antropométricas e motoras distintas, enfatizando a importância em acompanhar o desenvolvimento destas características de acordo com a idade....(AU)

The aim of the present study was to analyze and compare the anthropometric and motor characteristics of under 17, under 19 and Professional athletes. All data were collected prior to the beginning of the competitive season. The sample of this study was composed of 48 male soccer players divided into three groups: Under 17 (n=16), Under 19 (n=16) and Professional (n=16). To evaluate anthropometric characteristics, height and body composition were performed by means of air displacement pletismography. For determination of the motor characteristics the aerobic resistance test (Yo-Yo IR1), Counter movement jump (CMJ), Squat jump (SJ), performance of 5m and 30 m sprint and anaerobic power (RAST test) to determine the maximum, mean and minimum power were performed. To determine the differences between the categories regarding anthropometric and motor characteristics, a one-way ANOVA complemented with Bonferroni post-hoc test was used, with a level of significance of p>0,016. Professional athletes shown higher values of body weight and absolute lean mass compared to Under 17 and Under 19 categories, with no difference for absolute and relative fat mass and relative lean mass. No anthropometric differences were identified among athletes in the Under 17 and Under 19 categories. Professional athletes presented values of CMJ, SJ, sprint of 30m and maximal, mean, and minimum power higher than Under 17 and Under 19 athletes, with no difference in relation to Yo-Yo IR1 and sprint of 5m. Under 19 athletes presented higher values of Yo-Yo IR1 compared to Under 17 and Professionals, and higher values of CMJ, sprint of 30 m, mean and, minimum power compared to Under 17 athletes. Athletes of different categories present distinct anthropometric and motor characteristics, emphasizing the importance of accompanying the development of these characteristics according to playing age....(AU)

Effect of Overload and Tapering on Individual Heart Rate Variability, Stress Tolerance, and Intermittent Running Performance in Soccer Players During a Preseason.

Figueiredo, DH, Figueiredo, DH, Moreira, A, Gonçalves, HR, and Stanganelli, LCR. Effect of overload and tapering on individual heart rate variability, stress tolerance, and intermittent running performance in soccer players during a preseason. J Strength Cond Res 33(5): 1222-1231, 2019-This study evaluates the weekly natural log of the root-mean-square difference of successive R-R intervals (lnRMSSDmean), its coefficient of variation (lnRMSSDcv), training load (TL), stress tolerance (ST), and changes in intermittent running performance in response to a 2-week overload (OL) followed by a 1-week taper (TP) during a preseason. Additionally, we determined the relationships between these variables. Ultra-short lnRMSSD, psychometric responses, and ratings of perceived exertion were evaluated daily among 16 under-19 soccer players. At the end of each training phase, the athletes performed the Yo-Yo Intermittent Recovery test level 1 (Yo-Yo). Group analysis showed a decrease in lnRMSSDmean and ST, increases in lnRMSSDcv, and decreases in the Yo-Yo during OL, with a return to baseline levels and a trivial increase in the Yo-Yo during TP. Small to very large correlations were found between lnRMSSDmean and lnRMSSDcv values, with changes in Yo-Yo, TL, monotony, and strain during the preseason (r values ranging from -0.27 to 0.82). No correlation was found between lnRMSSD responses and ST. During OL, athletes with decreases in lnRMSSDmean and increases in lnRMSSDcv accumulated higher perceived TL, with higher monotony and overall stress, and presented a decrease in ST and intermittent running performance, interpreted as a negative adaptation in response to the maintenance of higher TL. During TP, these responses were reversed, leading to an increase in intermittent running performance. In addition, subjective measures of ST may be used to provide early indicators of training adaptation in soccer players.

Time limit at peak speed without prior warm-up: Effects on test duration, heart rate and rating of perceived exertion / Tiempo límite en la velocidad máxima sin calentamiento previo: efectos sobre la duración de la prueba, frecuencia cardíaca y grado de esfuerzo percibido

Background: Time limit (tlim) at peak speed (Vpeak), that is maximal time that an individual can keep running at maximal intensity, is used to prescribe interval durations during interval training. The aim of this study was to compare two protocols (without or with 15 minutes of warm-up) for the tlim determination at 100% of Vpeak in untrained men. Material and method: Twelve untrained young men performed three running tests on a treadmill: one maximal incremental test to determine Vpeak and two rectangular tests, performed in randomized order, without a warm-up (tlim0) or with a 15-minute warm-up duration (tlim15) at 60% of Vpeak to determine the tlim at 100% of Vpeak, after the warm-up the tests were performed at the speed of the individual Vpeak until volitional exhaustion. During the tests, heart rate (HR) and rating of perceived exertion (RPE) were monitored and blood lactate sampling was collected prior to session (LApre); immediately post-exercise (LA0-min); 3 min (LA3-min), 5 min (LA5-min) and 7 min (LA7-min) post-exercise to determine lactate concentrations. The Shapiro-Wilk test was used and confirmed the normality of the data distribution, with maximal and submaximal values compared using Student ́s t test for dependent samples. Results: Test duration at tlim0 was significant higher than that at tlim15 (P = 0.02). Additionally, different tlim protocols influenced HR and RPE submaximal responses and did not modify lactate concentrations or maximal variables (HRmax and RPEmax). Conclusions: These findings suggest that the determination of tlim at 100% of Vpeak without a prior warm-up led to a higher test duration in untrained men

Objetivos: Tiempo límite (tlim) en la velocidad máxima (Vpico), que es el tiempo máximo que un individuo puede permanecer corriendo en la intensidade máxima, se utiliza para prescribir la duración de los intervalos durante el entrenamiento interválico. El objetivo de este estudio fue comparar dos protocolos (sin o con 15 minutos de calentamiento) para la determinación de tlim al 100% de la Vpico en hombres no entrenados. Material y método: Doce jóvenes no entrenados realizaron tres pruebas de carrera en la cinta rodante: una prueba incremental máxima para determinar Vpico y dos pruebas rectangulares, realizadas en orden aleatorio, sin calentamiento (tlim0) o con una duración de calentamiento de 15 minutos (tlim15) al 60% de la Vpico para determinar el tlim al 100% de la Vpico; después del calentamiento las pruebas fueron realizadas en la velocidad de la Vpico individual hasta el agotamiento voluntario. Durante las pruebas, la frecuencia cardíaca (FC) y el grado de esfuerzo percibido (RPE) fueron monitorizadas y se tomaron muestras de sangre antes de la sesión (LApre); inmediatamente después del ejercicio (LA0-min); 3 min (LA3-min), 5 min (LA5-min) y 7 min (LA7-min) después del ejercicio para determinar las concentraciones de lactato. Se utilizó la prueba de Shapiro Wilk y se confirmó la normalidad de la distribución de los datos, con los valores máximos y submáximos comparados utilizando la prueba t de Student para muestras dependientes. Resultados: La duración de la prueba en el tlim0 fue significativamente mayor que aquella en el tlim15 (P = 0.02). Además, los diferentes protocolos de tlim influenciaron las respuestas submáximas de FC y RPE y no modificaron las concentraciones de lactato o las variables máximas (FCmax y RPEmax). Conclusiones: Estos resultados sugieren que la determinación del tlim en la 100% de la Vpico sin calentamiento prévio lleva a una mayor duración de la prueba em hombres no entrenados

Effects of chronic beetroot juice supplementation on maximum oxygen uptake, velocity associated with maximum oxygen uptake, and peak velocity in recreational runners: a double-blinded, randomized and crossover study.

PURPOSE: This study investigated the effects of chronic 3-day beetroot juice (BRJ) supplementation on maximum oxygen uptake (VO2max), velocity associated with VO2max(vVO2max), and peak velocity (Vpeak) in recreational runners. METHODS: Thirteen male recreational runners (age 28.2 ± 3.0 years, height 176.8 ± 0.1 cm, body mass 74.4 ± 9.5 kg) performed four tests on a treadmill in a randomized, double-blind, crossover design: two maximum incremental tests to determine VO2max and vVO2max, and two tests to determine Vpeak. Trials were performed following 3 days of supplementation of NO3--rich BRJ in natura (8.4 mmol NO3- day- 1) or BRJ NO3--depleted placebo (0.01 mmol NO3- day- 1), with the last dose being ingested 2 h before each test. During the tests, maximum heart rate (HRmax), maximal rating of perceived exertion (RPEmax), pre- and post-test glucose concentrations (Glucpre, Glucpost), and peak blood lactate concentration were determined. RESULTS: VO2max was higher following BRJ vs PLA (46.6 ± 6.4 vs 45.1 ± 5.8 mL kg- 1 min- 1; P = 0.022), as well as vVO2max (14.5 ± 0.8 vs 13.9 ± 1.0 km h- 1P = 0.024) and Vpeak (15.5 ± 1.1 vs 15.2 ± 1.2 km h- 1P = 0.038), with no differences in the other variables. CONCLUSION: Consumption of NO3--rich BRJ in natura (8.4 mmol NO3- day- 1) once per day for 3 days improved VO2max, vVO2max and Vpeak in recreational runners without changing the other analyzed variables.

Activation thresholds in epidemic spreading with motile infectious agents on scale-free networks.

We investigate a fermionic susceptible-infected-susceptible model with the mobility of infected individuals on uncorrelated scale-free networks with power-law degree distributions P ( k ) ∼ k - γ of exponents 2 < γ < 3 . Two diffusive processes with diffusion rate D of an infected vertex are considered. In the standard diffusion, one of the nearest-neighbors is chosen with equal chance, while in the biased diffusion, this choice happens with probability proportional to the neighbor's degree. A non-monotonic dependence of the epidemic threshold on D with an optimum diffusion rate D ∗ , for which the epidemic spreading is more efficient, is found for standard diffusion while monotonic decays are observed in the biased case. The epidemic thresholds go to zero as the network size is increased and the form that this happens depends on the diffusion rule and the degree exponent. We analytically investigated the dynamics using quenched and heterogeneous mean-field theories. The former presents, in general, a better performance for standard and the latter for biased diffusion models, indicating different activation mechanisms of the epidemic phases that are rationalized in terms of hubs or max k -core subgraphs.

Manipulation of pre and postnatal androgen environments and anogenital distance in rats.

We examined the anogenital distance (AGD) plasticity in rats through the manipulation of the androgen environment in utero and during puberty. Dams were treated from gestation days 13-20 with vehicle, flutamide (20mg/kg/day), di-(2-ethylhexyl) phthalate (DEHP, 750mg/kg/day), or testosterone (1.0mg/kg/day). After weaning, male pups were randomly assigned to one of four postnatal groups, which received the same treatments given prenatally. Sixteen treatment groups were established based on the combination of pre- and postnatal exposures. The postnatal treatments were conducted from postnatal days 23-53. In utero flutamide and DEHP exposure significantly shortened male AGD, although this effect was more pronounced in flutamide-exposed rats. Postnatal flutamide, DEHP, and testosterone induced slight but significant reductions in male AGD. Our study indicates that AGD is a stable anatomical landmark that reflects the androgen action in utero, although it can also be slightly responsive to changes in the androgen environment following pubertal exposure.

Mediator kinase inhibition further activates super-enhancer-associated genes in AML.

Super-enhancers (SEs), which are composed of large clusters of enhancers densely loaded with the Mediator complex, transcription factors and chromatin regulators, drive high expression of genes implicated in cell identity and disease, such as lineage-controlling transcription factors and oncogenes. BRD4 and CDK7 are positive regulators of SE-mediated transcription. By contrast, negative regulators of SE-associated genes have not been well described. Here we show that the Mediator-associated kinases cyclin-dependent kinase 8 (CDK8) and CDK19 restrain increased activation of key SE-associated genes in acute myeloid leukaemia (AML) cells. We report that the natural product cortistatin A (CA) selectively inhibits Mediator kinases, has anti-leukaemic activity in vitro and in vivo, and disproportionately induces upregulation of SE-associated genes in CA-sensitive AML cell lines but not in CA-insensitive cell lines. In AML cells, CA upregulated SE-associated genes with tumour suppressor and lineage-controlling functions, including the transcription factors CEBPA, IRF8, IRF1 and ETV6 (refs 6-8). The BRD4 inhibitor I-BET151 downregulated these SE-associated genes, yet also has anti-leukaemic activity. Individually increasing or decreasing the expression of these transcription factors suppressed AML cell growth, providing evidence that leukaemia cells are sensitive to the dosage of SE-associated genes. Our results demonstrate that Mediator kinases can negatively regulate SE-associated gene expression in specific cell types, and can be pharmacologically targeted as a therapeutic approach to AML.

Assessing the potential biological implications of recreational inshore fisheries on sub-tidal fish communities of Azores (north-east Atlantic Ocean) using catch and effort data.

Recreational inshore fishing activities practiced on Faial and Pico Islands (Azorean archipelago) were surveyed between October 2004 and September 2005. Recreational inshore fishers employ three main methods of fishing (shore angling, spear fishing and intertidal collecting). The method that demanded the highest fishing effort (number of fishing operations) was shore angling, followed by intertidal collecting and spear fishing. Shore angling produced the highest diversity of catch composition (38), which is in part explained by the seven fishing techniques used by shore anglers. The estimates of annual catch were higher for shore angling than spear fishing (51·2 and 6·3 t) even though they were lower than commercial artisanal fishing (442 t). The weighted mean trophic level and vulnerability index values in the fish catch were higher for spear fishing (3·4 and 50·9) than for shore angling (3·1 and 44·5). Cumulative pressure by different recreational fishing activities was detected on species already subject to a heavy pressure from Azorean commercial fishing, and on vulnerable and top-predator species. There are important biological and ecological implications whereby fishery managers should implement additional regulations such as prohibiting catches of the most vulnerable species.

[The association between socioeconomic indicators andadolescents'physical activity and health-related fitness]. / Associação entre indicadores socioeconômicos com a atividade física e aptidão física relacionada à saúde em adolescentes.

OBJECTIVE: This study was aimed at analysing the association between socioeconomic indicators and adolescents' physical activity and health-related fitness. METHODS: The study involved 716 adolescents from both genders whose age ranged from 10 to 18 years-old (46.8% male) who answered a questionnaire for estimating their habitual physical activity, socioeconomic status; two health-related physical fitness tests were also performed. The socioeconomic indicators analysed concerned their parents' educational level and the number of bathrooms, TVs, cars, housemaids, refrigerators and freezers in their homes. RESULTS: A positive association was found between paternal education (PR=1.61 (range 1.27-2.10) and 1.41 (1.10-1.83)) and housemaids (PR=1.97 (1.04-3.81) and 1.92 (1.05-3.52)) with recommended physical activity and leisure time physical activity, respectively. The number of cars (PR=1.48: 1.02-2.19) and freezers (PR=1.88: 1.12-3.18) was positively associated with leisure time physical activity and the number of TVs negatively so (PR=0.75: 0.63-0.89). The number of TVs (PR=0.80: 0.67-0.96) and cars (PR=0.70: 0.55-0.89) was negatively associated with cardiorespiratory fitness whilst paternal education (PR=1.17: 1.00-1.37) and the number of bathrooms in the home (PR=1.25: 1.02-1.54) were positively associated with muscular strength. CONCLUSION: Physical activity and health-related physical fitness were associated with socioeconomic status. However, such association depended on the socioeconomic indicator being analysed. Caution should be taken when analysing studies which use different socioeconomic indicators.

Reproductive evaluation of two pesticides combined (deltamethrin and endosulfan) in female rats.

Data from in vitro studies suggest that the pesticides deltamethrin (D) and endosulfan (E) exert estrogen-like effects. There is concern that interaction between weakly estrogenic compounds can increase their estrogenic potency. The aim of the present study was to determine estrogenic activity in an animal model and the possible female reproductive adverse effects of these pesticides combined. Wistar rats received daily (po), from day 6 of pregnancy to day 21 of lactation, deltamethrin and endosulfan concomitantly: D: 2.0 mg/kg+E: 1.5 mg/kg, or D: 3.0 mg/kg+E: 2.0 mg/kg, or D: 4.0 mg/kg+E: 3.0mg/kg. Some offspring also were exposed directly after weaning. Maternal and reproductive outcome data were assessed. An uterotrophic assay to screen in vivo estrogenic activity of D+E was also performed. A group of female offspring was analyzed for vaginal opening (VO), first estrus, estrous cycle regularity, and weights of the uterus and ovaries. No signs of maternal toxicity were detected. Results from the uterotrophic assay indicate absence of in vivo estrogenic activity of D+E. No significant variations in reproductive endpoints of females were observed. These results suggest that administration of D+E does not pose a reproductive hazard to female rats exposed during critical periods of development, indicating that the combination does not exert estrogen-like effects in vivo or is not delivered to target organs.

Energetics of C-Cl, C-Br, and C-I bonds in haloacetic acids: enthalpies of formation of XCH2COOH (X=CI, Br, I) compounds and the carboxymethyl radical.

The standard molar enthalpies of formation of chloro-, bromo-, and iodoacetic acids in the crystalline state, at 298.15 K, were determined as deltafH(o)m(C2H3O2Cl, cr alpha)=-(509.74+/- 0.49) kJ x mol(-1), deltafH(o)m(C2H3O2Br, cr I)-(466.98 +/- 1.08) kJ x mol(-1), and deltafH(o)m (C2H3O2I, cr)=-(415.44 +/- 1.53) kJ x mol(-1), respectively, by rotating-bomb combustion calorimetry. Vapor pressure versus temperature measurements by the Knudsen effusion method led to deltasubH(o)m(C2H3O2Cl)=(82.19 +/- 0.92) kJ x mol(-1), deltasubH(o)m(C2H3O2Br)=(83.50 +/- 2.95) kJ x mol(-1), and deltasubH(o)m-(C2H3O2I) = (86.47 +/- 1.02) kJ x mol(-1), at 298.15 K. From the obtained deltafH(o)m(cr) and deltasubH(o)m values it was possible to derive deltafH(o)m(C2H3O2Cl, g)=-(427.55 +/- 1.04) kJ x mol(-1), deltafH(o)m (C2H3O2Br, g)=-(383.48 +/- 3.14) kJ x mol(-1), and deltafH(o)m(C2H3O2I, g)=-(328.97 +/- 1.84) kJ x mol(-1). These data, taken with a published value of the enthalpy of formation of acetic acid, and the enthalpy of formation of the carboxymethyl radical, deltafH(o)m(CH2COOH, g)=-(238 +/- 2) kJ x mol(-1), obtained from density functional theory calculations, led to DHo(H-CH2COOH)=(412.8 +/- 3.2) kJ x mol(-1), DHo(Cl-CH2COOH)=(310.9 +/- 2.2) kJ x mol(-1), DHo(Br-CH2COOH)=(257.4 +/- 3.7) kJ x mol(-1), and DHo(I-CH2COOH)=(197.8 +/- 2.7) kJ x mol(-1). A discussion of the C-X bonding energetics in XCH2COOH, CH3X, C2H5X, C2H3X, and C6H5X (X=H, Cl, Br, I) compounds is presented.