Maternal exposure to tributyltin alters the breast milk, hormonal profile, and thyroid morphology of dams and induces sex-specific changes in neonate rat offspring

Tributyltin (TBT) is the chemical substance commonly used worldwide to prevent biofouling of vessels. Due to its ability to bioaccumulate and biomagnify, even after being banned, significant concentrations of TBT can be detected in sediment, affecting marine and human life. Although studies have shown that direct exposure to TBT alters physiological parameters in mammals, the relationship between exposure to TBT during pregnancy and lactation, considered critical windows for metabolic programming, has not been fully elucidated. Our hypothesis is that offspring whose mothers were exposed to TBT during critical stages of development may exhibit dysfunctions in endocrine-metabolic parameters. We used pregnant Wistar rats that were divided into groups and received the following treatments from gestational day 7 until the end of lactation by intragastric gavage: vehicle (ethanol 0.01%; Control), low TBT dose (100 ng/kg of body weight (bw)/day; TBT100ng) and high TBT dose (1000 ng/kg bw/day; TBT1000ng). Dams and offspring at birth and weaning (21 days old) were studied. Maternal exposure to TBT promoted dose-dependent changes in dams. The findings for adiposity, milk composition and lipid profile were more pronounced in TBT100 ng dam; however, thyroid morphology was altered in TBT1000 ng dam. Female offspring were differentially affected by the dose of exposure. At birth, females in the TBT100ng group had low body weight, lower naso-anal length (NAL), and higher plasma T4, and at weaning, females in the TBT100ng group had lower insulin and leptin levels. Females in the TBT1000ng group had lower NAL at birth and lower leptinemia and weight of white adipose tissue at weaning. Male offspring from TBT groups showed high T3 at birth, without biometric alterations at birth or weaning. Despite these findings, both sexes exhibited dose-dependent morphological changes in the thyroid gland. Thus, maternal exposure to TBT constitutes an important route of contamination for both dams and offspring.

Exertional fatigue, sleep loss, and negative energy balance increase susceptibility to hypothermia

The purpose of this study was to determine how chronic exertional fatigue and sleep deprivation coupled with negative energy balance affect thermoregulation during cold exposure. Eight men wearing only shorts and socks sat quietly during 4-h cold air exposure (10 degreesC) immediately after (<2 h, A) they completed 61 days of strenuous military training (energy expenditure approximately 4,150 kcal/day, energy intake approximately 3,300 kcal/day, sleep approximately 4 h/day) and again after short (48 h, SR) and long (109 days, LR) recovery. Body weight decreased 7.4 kg from before training to A, then increased 6.4 kg by SR, with an additional 6.4 kg increase by LR. Body fat averaged 12% during A and SR and increased to 21% during LR. Rectal temperature (Tre) was lower before and during cold air exposure for A than for SR and LR. Tre declined during cold exposure in A and SR but not LR. Mean weighted skin temperature (Tsk) during cold exposure was higher in A and SR than in LR. Metabolic rate increased during all cold exposures, but it was lower during A and LR than SR. The mean body temperature (0.67 Tre + 0.33 Tsk) threshold for increasing metabolism was lower during A than SR and LR. Thus chronic exertional fatigue and sleep loss, combined with underfeeding, reduced tissue insulation and blunted metabolic heat production, which compromised maintenance of body temperature. A short period of rest, sleep, and refeeding restored the thermogenic response to cold, but thermal balance in the cold remained compromised until after several weeks of recovery when tissue insulation had been restored.

Effects of three hydration beverages on exercise performance during 60 hours of heat exposure

Without adequate hydration, profound heat stress and dehydration can occur in people who work in hot environments. This study evaluated the effectiveness of three beverages on temperature regulation, cardiovascular response, and work performance during 60 h of dry heat exposure. Volunteer subjects lived in a climatic chamber in simulated desert conditions varying from 25-45 degrees C at 20% relative humidity. They performed three submaximal exercise sessions on a motorized treadmill at 4-h intervals each day. All of the subjects consumed one of three beverages: a water placebo, a 5% carbohydrate-electrolyte drink, or a 4% carbohydrate-electrolyte drink containing 1% glycerol, during each 60-h session. During exercise, the rating of perceived exertion and heart rate were similar for all beverages and all sessions, but oxygen consumption, core body and average skin temperatures, and sweat rate differed among beverages and sessions. Water alone appeared to provide adequate hydration for working in desert conditions over the 60 h when compared to carbohydrate-electrolyte beverages, with or without a small amount of glycerol.

The effects of strength training and centrifuge exposure on +Gz tolerance

Weight training (WT) as a countermeasure to +Gz intolerance seems to be an accepted modality, but lacks convincing support in the research literature. This study examines factors associated with WT in an operational environment as a countermeasure to +Gz intolerance. Fourteen naval aviators were assigned to a WT group (n = 7) and a non-weight-trained control (NWT) group (n = 7). All subjects were tested before and after a 10-week training period for aerobic capacity (VO2max), dynamic muscular strength (Cybex II), body fat, gradual onset rate (GOR) for +Gz at a rate of +1 G.15 s-1, and finally a simulated air combat maneuver (SACM) consisting of 15 s at +4.5 Gz and +7 Gz alternating challenges to exhaustion. The results indicate the following: 1) no significant differences in any of the centrifuge variables measured between WT and NWT groups while both groups showed a time or learning effect in SACM from 175 +/- 109 to 239 +/- 110 s (grouped data df = 16, t = 2.97, p < 0.09); 2) no improvement in SACM time for subjects achieving a 300-s SACM pretest value (n = 4); and 3) for SACM times below 300 s, the WT subjects showed a greater improvement than NWT subjects (n = 11, F = 9.12, p < 0.02). The data suggest that although some subjects showed considerable strength gains, WT in a naval aviation operational setting may not provide a universal desired effect.(ABSTRACT TRUNCATED AT 250 WORDS)