2,6-Di-bromo-4-methyl-aniline.

In the title compound, C7H7Br2N, the C-C-C bond angles of the benzene ring are notably distorted and two short intamolecular N-H⋯Br contacts occur. In the crystal, the mol-ecules are linked by N-H⋯N hydrogen bonds to generate C(2) chains propagating in the [100] direction.

No effect of menstrual cycle phase on glucose and glucoregulatory endocrine responses to prolonged exercise.

INTRODUCTION: Prolonged exercise requires increased utilization of blood glucose and adjustment of glucoregulatory hormones. Estrogen can reduce hepatic gluconeogenesis which could affect insulin concentrations. Amylin is co-secreted with insulin and controls influx of glucose into the blood. PURPOSE: To determine the effect of menstrual cycle stage on glucose, leptin, and pancreatic hormone responses to prolonged (90 min) exercise. METHODS: Five healthy, eumenorrheic women (24.6 ± 5.1 years; 67.4 ± 1 kg) were monitored for 3 months to determine menstrual cycle length. Subjects completed a preliminary session to determine exercise workloads and, in a fasted condition, completed two randomized 90-min treadmill exercise trials at 60 % VO2max during the early follicular (EFX) and mid-luteal phase (MLX) of their menstrual cycle. Blood samples were analyzed for glucose, insulin, C-peptide, amylin, glucagon, leptin, and cortisol concentrations at rest (-30 and 0 min), during exercise (18, 36, 54, 72, and 90 min) and after 20 min of recovery. RESULTS: No changes in amylin, leptin, or cortisol occurred for EFX and MLX trials. A significant (p < 0.05) time effect occurred for glucose, insulin, and glucagon with reduced insulin across the exercise trial and increases in glucose and glucagon later in the trial, but there were no differences between the EFX and MLX trials. CONCLUSIONS: Menstrual cycle stage does not affect glucose, insulin, C-peptide, amylin, glucagon, cortisol, and leptin responses to prolonged exercise; however, the exercise reduces insulin and increases glucose and glucagon concentrations. This is the first study to determine acute effects of exercise on amylin and other glucoregulatory hormone responses in women.

Estrogen mediation of hormone responses to exercise.

The roles of estrogens extend from the regulation of reproduction to other functions involved in control of metabolism, fluid balance, as well as gastrointestinal, lung, and brain function, with a strong effect on other hormones that subsequently alter the physiology of multiple tissues. As such, alteration of endogenous estrogens across the menstrual cycle, or from oral contraception and estrogen replacement therapy, can affect these tissues. Due to the important effects that estrogens have on different tissues, there are many investigations concerning the effects of a human estrogenic environment on endocrine responses to exercise. The following review will describe the consequences of varying estrogen levels on pituitary, adrenal, gonadal, and endocrine function, followed by discussion of the outcomes of different estrogen levels on endocrine tissues in response to exercise, problems encountered for interpretation of findings, and recommended direction for future research.

Effects of prolonged exercise on agouti-related protein: a pilot study.

Agouti-related protein (AgRP), is a signaling peptide that affects feeding behavior, energy homeostasis, and has also been shown to stimulate the hypothalamic-pituitary-adrenal axis. The purpose of this study was to determine the effects of 90 min of treadmill exercise on circulating AgRP concentrations and the relationship of AgRP responses to cortisol. Seven young males completed a preliminary trial followed by counterbalanced experimental and control trials 4-5 weeks apart. The experimental trial began 2.5 h after consumption of a standard nutrient beverage and consisted of treadmill exercise at 60 % of previously determined VO(2max) for 90 min. Blood samples were collected before (-30 and 0 min), during (18, 36, 54, 72, and 90 min), and following exercise (20, 40, and 60 min). Blood samples were collected in a resting, control trial at the same time points as the experimental trial. Plasma lactate was significantly higher in the exercise than the control trial. Although AgRP increased from 18 min of exercise to peak at 90 min, these increases were not significantly different than values in the control trial. Cortisol responses during the exercise trial were significantly higher than the control trial. AgRP concentrations during early exercise were positively correlated with cortisol levels later in recovery. The obtained data suggest that AgRP concentrations during prolonged steady-state exercise are associated with subsequent cortisol increases, but further study is required to determine whether there is a causal effect.

Amylin and selective glucoregulatory peptide alterations during prolonged exercise.

UNLABELLED: Amylin is a pancreatic ß-cell peptide that facilitates the regulation of blood glucose concentration by inhibiting release of glucagon and modulating gastric emptying. Prolonged exercise may alter amylin and aid in the maintenance of blood glucose concentration; however, no studies have investigated the effects of prolonged exercise on amylin. PURPOSE: This study aimed to determine the effects of 90 min of treadmill exercise on amylin and other glucoregulatory hormone responses in a postprandial state. METHODS: Eight young healthy males completed a preliminary trial for VO2max and body composition determination and subsequent experimental and control trials in a counterbalanced manner. The experimental trial subjects arrived at the laboratory at 8:00 a.m., 1 h after consumption of a standard nutrient beverage (Ensure Plus®). At 9:50 a.m., subjects initiated 90 min of treadmill exercise at 60% of VO2max. Blood samples were collected twice before exercise, every 18 min during exercise, and every 20 min during 1 h of recovery. A resting control trial was conducted in an identical manner without VO2 assessment. RESULTS: Plasma glucose and leptin concentrations remained stable across exercise, whereas lactate significantly increased to peak at 18 min of exercise then gradually declined. Amylin, insulin, and C-peptide values significantly declined over the trials, with no difference between exercise and control days. Glucagon area-under-the-curve concentrations were significantly greater during the exercise than the control trials. There was a significant time effect and trial effect for cortisol with a higher concentration during the experimental trial than during the control trial. CONCLUSIONS: In a postprandial state, prolonged exercise stimulates glucagon and cortisol increases that are associated with stable blood glucose and leptin concentrations; however, similar to postprandial state control condition, insulin, C-peptide, and amylin concentrations decline.

Partial occlusion during resistance exercise alters effort sense and pain.

The purpose of the study was to determine how manipulation of peripheral blood flow during resistance exercise using a light load affected perception and physiological measures compared with moderate load resistance exercise and a control trial. Seven subjects performed a 3 (session) by 2 (biceps curls and calf extensions) within-subjects study that was randomized and counterbalanced across 3 weeks. The 3 sessions included (a) light resistance exercise (3 sets to failure) at 30% of 1 repetition maximum (1RM) with partial occlusion (LRO), (b) moderate resistance at 70% of 1RM with no occlusion (MR), and (c) partial occlusion without exercise (OO). Ratings of perceived exertion (RPE), pain, and heart rate were assessed immediately after each set, whereas blood samples were taken before, immediately after, and 15 minutes after exercise. Results demonstrated that RPE and pain were lower in the OO condition than that in the MR and LRO conditions for biceps curls and calf extensions, Fs(2 ,24) = 22.75, 20.86, ps < 0.0001 and Fs(2,24) = 18.95, 24.52, ps < 0.01; however, no significant differences were noted between MR and LRO conditions. Heart rate was significantly higher for the LRO condition when compared with the MR trial, F(2,18) 20.12, p < 0.001. Results suggest that when partial vascular occlusion with a light load was applied, both pain and effort sense were altered to a similar degree as moderate loads but no occlusion. The practical application of results were that individuals may be better able to tolerate perceptual change at low loads with partial occlusion because joint stress may be minimized while local muscle metabolic demands increase, making resistance training maximally effective and minimally stressful on joints. Perceptual tracking of effort and pain may aid coaches who attempt this protocol.

Load rather than contraction type influences rate of perceived exertion and pain.

The purpose of the study was to determine whether muscle contraction type (concentric [CON] or eccentric [ECC]) or loading (relative or absolute) has a greater impact on the perceptual and metabolic responses to conventional resistance exercise. Additionally, overall effort, pain sensations, and specific pain descriptors were compared with physiological responses. Seven healthy men (mean +/- SE, 25.71 +/- 2.17 years) with resistance training experience completed 2 one-repetition maximum (1-RM) trials. Subsequently, 2 randomized, counterbalanced, experimental sessions were completed consisting of 4 sets of 10 repetitions for 6 exercises. These sessions were performed at 65% CON 1-RM for CON only contractions or 65% CON 1-RM + 20% for ECC contractions. Blood samples were taken pre, post, and 15 minutes postexercise. OMNI-RPE (OMNI-Res), CR-10 pain rating, McGill pain ratings, and heart rate (HR) were recorded after each set. A significant time effect occurred for OMNI-Res, pain, lactate, and HR (p < 0.05). No significant pattern emerged for the contraction type, except for higher HR and lactate immediately postexercise for the CON contractions. Physiological measures were not significantly related to perceptual measures. When considered with previous data, muscle loading rather than contraction type plays the primary role in perceptual alterations of effort sense and pain. Practical applications of the investigation are that strength and conditioning professionals may be able to load CON and ECC contractions in a relative fashion by increasing loads in the ECC portion by 20% above the CON load that would result in comparable perceptual experiences.

Notch signaling links interactions between the C/EBP homolog slow border cells and the GILZ homolog bunched during cell migration.

In the follicle cell (FC) epithelium that surrounds the Drosophila egg, a complex set of cell signals specifies two cell fates that pattern the eggshell: the anterior centripetal FC that produce the operculum and the posterior columnar FC that produce the main body eggshell structure. We have previously shown that the long-range morphogen DPP represses the expression of the bunched (bun) gene in the anterior-most centripetal FC. bun, which encodes a homolog of vertebrate TSC-22/GILZ, in turn represses anterior gene expression and antagonizes Notch signaling to restrict centripetal FC fates in posterior cells. From a screen for novel targets of bun repression we have identified the C/EBP homolog slow border cells (slbo). At stage 10A, slbo expression overlaps bun in anterior FC; by stage 10B they repress each other's expression to establish a sharp slbo/bun expression boundary. The precise position of the slbo/bun expression boundary is sensitive to Notch signaling, which is required for both slbo activation and bun repression. As centripetal migration proceeds from stages 10B-14, slbo represses its own expression and both slbo loss-of-function mutations and overexpression approaches reveal that slbo is required to coordinate centripetal migration with nurse cell dumping. We propose that in anterior FC exposed to a Dpp morphogen gradient, high and low levels of slbo and bun, respectively, are established by modulation of Notch signaling to direct threshold cell fates. Interactions among Notch, slbo and bun resemble a conserved signaling cassette that regulates mammalian adipocyte differentiation.

Maximal eccentric and concentric strength discrepancies between young men and women for dynamic resistance exercise.

Although research has demonstrated that isokinetic eccentric (ECC) strength is 20-60% greater than isokinetic concentric (CON) strength, few data exist comparing these strength differences in standard dynamic resistance exercises. The purpose of the study was to determine the difference in maximal dynamic ECC and CON strength for 6 different resistance exercises in young men and women. Ten healthy young men (mean +/- SE, 25.30 +/- 1.34 years), and 10 healthy young women (mean +/- SE, 23.40 +/- 1.37 years) who were regular exercisers with resistance training experience participated in the study. Two sessions were performed to determine CON and ECC 1 repetitions maximum for latissimus pull-down (LTP), leg press (LP), bench press (BP), leg extension (LE), seated military press (MP), and leg curl (LC) exercises. Maximal ECC and maximal CON strength were determined on weight stack machines modified to isolate ECC and CON contractions using steel bars and pulleys such that only 1 type of contraction was performed. Within 2 weeks, participants returned and completed a retest trial in a counterbalanced fashioned. Test-retest reliability was excellent (r = 0.99) for all resistance exercise trials. Men demonstrated 20-60% greater ECC than CON strength (LTP = 32%, LP = 44%, BP = 40%, LE = 35%, MP = 49%, LC = 27%). Women's strength exceeded the proposed parameters for greater ECC strength in 4 exercises, p < 0.05 (LP = 66%, BP = 146%, MP = 161%, LC = 82%). The ECC/CON assessment could help coaches capitalize on muscle strength differences in young men and women during training to aid in program design and injury prevention and to enhance strength development.

Comparison of hormone responses following light resistance exercise with partial vascular occlusion and moderately difficult resistance exercise without occlusion.

Previous studies of contracting muscle with low loading and partial vascular occlusion demonstrated hypertrophy and strength adaptations similar to and exceeding those observed with traditional moderate to high resistance (Shinohara M, Kouzaki M, Yoshihisa T, and Fukunaga T. Eur J Physiol 77: 189-191, 1998; Takarada Y, Takazawa H, Sato Y, Takebayashi S, Tanaka Y, and Ishii N. J Appl Physiol 88: 2097-2106, 2000; Takarada Y, Sato Y, and Ishii N. Eur J Physiol 86: 308-314, 2002). The purpose of the study was to determine the anabolic and catabolic hormone responses to light resistance exercise combined with partial vascular occlusion. Three experimental conditions of light resistance with partial occlusion (LRO), moderate resistance with no occlusion (MR), and partial occlusion without exercise (OO) were performed by eight healthy subjects [mean 21 yr (SD 1.8)]. Three sets of single-arm biceps curls and single-leg calf presses were completed to failure with 1-min interset rest periods. Workloads of 30 and 70% one repetition maximum for each exercise were lifted for the LRO and MR trials, respectively. Blood samples were taken preexercise, postexercise, and 15 min postexercise for each experimental condition. Lactate increased significantly in the LRO and MR trials and was not significantly different from each other at any time point. Growth hormone (GH) increased significantly by fourfold from pre- to postexercise in the LRO session but did not change significantly during this time period in the MR and OO trials (8.3 +/- 2.3 vs. 2.1 +/- 1.2 and 2.6 +/- 0.94 microg/l; respectively, P < 0.05). There were no changes in resting total testosterone [T; mean 15.7 +/- 1.6 (SE) nmol/l], free testosterone (FT; 54.1 +/- 4.5 pmol/l), or cortisol (267.6 +/- 22 nmol/l) across all trials and times. In conclusion, with similar lactate responses, light exercise combined with partial vascular occlusion elicits a greater GH response than moderate exercise without occlusion but does not affect T, FT, or cortisol.

Similar hormonal responses to concentric and eccentric muscle actions using relative loading.

Conventional resistance exercise is performed using sequential concentric (CON) and eccentric (ECC) contractions, utilizing the same muscle load. Thus, relative to maximal CON and ECC resistance, the ECC contraction is loaded to a lesser degree. We have recently shown that at the same absolute load, CON contractions are associated with greater growth hormone (GH) but similar total testosterone (TT) and free testosterone (FT) responses compared with ECC contractions and attributed the larger GH response to greater relative CON loading. In the present study, we have examined the same endocrine parameters to six different upper and lower body exercises using relative loading rather than absolute loading, hypothesizing that GH responses would be similar for CON and ECC actions, but TT and FT responses would be greater after ECC contractions. Seven young men with recreational weight training experience completed an ECC and CON muscle contraction trial on two different occasions in a counterbalanced fashion. The exercises consisted of four sets of 10 repetitions of lat pull-down, leg press, bench press, leg extension, military press, and leg curl exercises at 65% of an ECC or CON 1-RM with 90 s between sets and exercises. CON and ECC actions were performed at the same speed. ECC 1-RMs were considered to be 120% of the CON 1-RM for the same exercise. Blood samples were collected before, immediately after, and 15 min after the exercise. GH significantly increased across both trials but was not different between the two trials. Total testosterone was not significantly altered in response to either trial; however, free testosterone concentrations increased in response to both ECC and CON trials. Data suggest that CON and ECC muscle contractions produce similar GH, T, and free testosterone responses with the same relative loading.