Gene/Protein Disease Symptom Drug Enzyme Compound
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Many types of drugs are used by athletes to improve performance. This paper reviews the literature on 3 categories of drugs: those that enhance performance as stimulants (amphetamines, ephedrine, and cocaine), those that are used to reduce tremor and heart rate (beta-blockers) and those involved in bodyweight gain or loss (anabolic-androgenic steroids, growth hormone, beta 2-agonists, and diuretics). Limitations of research on these drugs as they relate to performance enhancement are also discussed. The numerous studies that have assessed the effects of amphetamines on performance report equivocal results. This may be due to the large interindividual variability in the response to the drug and the small sample sizes used. Most studies, however, show that some individuals do improve exercise performance when taking amphetamines, which may be attributed to their role in masking fatigue. As a stimulant, ephedrine has not been found to improve performance in the few studies available. More recently, ephedrine has been purported to be effective as a fat burner and used by athletes to maintain or improve muscle mass. Although research on individuals with obesity supports the use of ephedrine for fat loss, no studies have been done on athletes. The few studies of cocaine and exercise suggest that little to no performance gains are incurred from cocaine use. Moreover, the sense of euphoria may provide the illusion of better performance when, in actuality, performance was not improved or was impaired. beta-Blockers have been found to reduce heart rate and tremor and to improve performance in sports that are not physiologically challenging but require accuracy (e.g. pistol shooting). However, there is evidence that some individuals may be high responders to beta-blockers to the extent that their heart rate response is so blunted as to impair performance. Although equivocal, several studies have reported that anabolic-androgenic steroids increase muscle size and strength. However, most studies are not well controlled and use insufficient drug doses. One recent well controlled study did find an increase in muscle mass and strength with supraphysiological doses, and the improvements were greater in participants who were also resistance training. There is little information available on the effects of growth hormone on muscle mass or performance in athletes, although data suggest that growth hormone administration does not increase muscle protein synthesis. beta 2-Agonists, such as clenbuterol and salbutamol, when administered orally appear to improve muscular strength due to their potential role in increasing muscle mass. However, studies have not been done using athletes. Diuretics results in a loss of body water and hence bodyweight that can be advantageous for sports with strict bodyweight classifications. There is insufficient evidence on possible performance decrements in the field that could result from dehydration induced by the diuretics. Overall, the most significant concern in studies of drug use is the large inter-individual variability in responses to a drug. Further studies are needed to understand why some individuals are more responsive than others and to assess whether the responses are consistent for a given individual. Most studies of drug effectiveness have not used athletes. The effectiveness of many drugs may be reduced in highly trained athletes because there is a lower margin for improvement.
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PMID:Drugs and sport. Research findings and limitations. 942 62

Water is an essential nutrient required for life. To be well hydrated, the average sedentary adult man must consume at least 2,900 mL (12 c) fluid per day, and the average sedentary adult woman at least 2,200 mL (9 c) fluid per day, in the form of noncaffeinated, nonalcoholic beverages, soups, and foods. Solid foods contribute approximately 1,000 mL (4 c) water, with an additional 250 mL (1 c) coming from the water of oxidation. The Nationwide Food Consumption Surveys indicate that a portion of the population may be chronically mildly dehydrated. Several factors may increase the likelihood of chronic, mild dehydration, including a poor thirst mechanism, dissatisfaction with the taste of water, common consumption of the natural diuretics caffeine and alcohol, participation in exercise, and environmental conditions. Dehydration of as little as 2% loss of body weight results in impaired physiological and performance responses. New research indicates that fluid consumption in general and water consumption in particular can have an effect on the risk of urinary stone disease; cancers of the breast, colon, and urinary tract; childhood and adolescent obesity; mitral valve prolapse; salivary gland function; and overall health in the elderly. Dietitians should be encouraged to promote and monitor fluid and water intake among all of their clients and patients through education and to help them design a fluid intake plan. The influence of chronic mild dehydration on health and disease merits further research.
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PMID:Water: an essential but overlooked nutrient. 997 88

Evidence of the validity and accuracy of dual x-ray absorptiometry (DXA) to measure soft-tissue composition of laboratory rats with altered body composition associated with nutritional perturbations is lacking. We compared DXA determinations made in prone and supine positions with measurements of chemical composition of 49 male, weanling Sprague-Dawley rats that were fed the basal AIN-93 growth diet, were fed the basal diet modified to contain 30% fat, were fasted for 2 d, were limit fed 6 g of the basal diet daily for 1 wk, or were treated with furosemide (10 mg/kg intraperitoneally 2 h before DXA). DXA produced similar estimates of body mass and soft-tissue composition in the prone and supine positions. DXA estimates of body composition were significantly correlated with reference composition values (R(2) = 0.371-0.999). DXA discriminated treatment effects on body mass, fat-free and bone-free mass, fat mass, and body fatness; it significantly underestimated body mass (1% to 2%) and fat-free and bone-free mass (3%) and significantly overestimated fat mass and body fatness (3% to 25%). The greatest errors occurred in treatment groups in which body mass was diminished and body hydration was decreased. These findings suggest that DXA can determine small changes in fat-free, bone-free mass in response to obesity and weight loss. Errors in DXA determination of fat mass and body fatness associated with extra corporeal fluid and dehydration indicate the need for revision of calculation algorithms for soft-tissue determination.
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PMID:Validation of dual x-ray absorptiometry for body-composition assessment of rats exposed to dietary stressors. 1144 99

The association between long haul travel and the risk of venous thromboembolism are suspected for long time. Mostly air travel related thrombosis series have been reported in the literature. Risk factors can be classified as: 1. travel related factors (coach position, immobilization, prolonged air travel, narrow seat and room, diuretic effect of alcohol, insufficient fluid intake, dehydration, direct pressure on leg veins, rare inspiration). 2. air plane related risk factors (low humidity, relative hypoxia, stress). 3. patient related factors (hereditary and acquired thrombophylia, previous deep venous thrombosis, age over 40, recent surgery or trauma, gravidity, puerperium, oestrogen containing pills, varicosity, chronic heart disease, obesity, fever, diarrhoea, vomiting, smoking). No patient related factors were found in some cases. To reduce the hazards air travellers are rightly concerned to know the level of the risk and the airlines should be responsible for this information. People should discuss with their physician what prophlylactic measures should be taken, such as compression stockings or low molecular weight heparin. Not only flight but car, bus and train travellers are also at risk of developing venous thromboembolism. Long haul travel alone is a separate risk factor for venous thromboembolism.
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PMID:[Thromboembolism in travelers]. 1177 54

Breast milk is the most appropriate food for infants. At least 4-6 months of breast feeding is sufficient for all babies if appropriate growth is monitored monthly. However, for those infants unable to breast-feed sufficiently or at all, formula can be given as an alternative. However, serious health problems such as hypernatremic dehydration, malnutrition, and obesity may develop if powdered formula is not appropriately prepared. In the present study, our aim was to investigate whether or not mothers of formula-fed babies in Ozkanlar (Izmir, Turkey) district prepared powdered infant formula appropriately. For this purpose, we visited all (328) families with infants younger than 12 months of age. Forty-two (13%) of these 328 infants were still fed formula. The mothers of the infants were asked to prepare formula for two different meals, and duplicate samples from each prepared formula were taken for the measurement of dry matter. Fifty percent of the mothers diluted formula with 10% more or 10% less water for the second meal as compared with the first meal. Four (10%) mothers diluted formula with 10% or less of the required water, while 27 (64%) prepared formula with 10% or more of the required water. It is concluded that mothers must be informed about the preparation of formula when formula is prescribed for their babies.
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PMID:A generally neglected threat in infant nutrition: incorrect preparation of infant formulae. 1245 4

The hypothalamus is critically involved in energy homeostasis and is an appropriate focus for research investigating the central neural underpinnings of obesity, anorexia and normal food intake. However, little is known regarding pathways and mechanisms that convey relevant hypothalamic signals to the brainstem circuits that ultimately control ingestive behavior. This brief review highlights work investigating the postnatal development of hypothalamic inputs to the hindbrain dorsal vagal complex (DVC). Research findings indicate that these inputs are both structurally and functionally immature in newborn rats. The progressive postnatal maturation of descending projections to the DVC occurs in concert with newly emerging physiological and behavioral responses to osmotic dehydration, which inhibits gastric emptying and food intake in adult animals but not in neonates. The postnatal emergence of other intake controls might also reflect progressive engagement of DVC neural circuits, whose intrinsic components and output pathways are envisioned as being critical for initiating and terminating ingestive behavior.
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PMID:Postnatal development of hypothalamic inputs to the dorsal vagal complex in rats. 1281 10

Nursing sickness, the largest single cause of mortality in adult female mink (Mustela vison), is an example of a metabolic disorder, which develops when the demands for lactation require extensive mobilization of body energy reserves. The condition is characterized by progressive weight loss, emaciation, and dehydration with high concentrations of glucose and insulin in the blood. Morbidity due to nursing sickness can be as high as 15% with mortality around 8%, but the incidence is known to vary from year to year. Stress has been shown to trigger the onset of the disease and old females and females with large litters are most often affected. Increasing demand for gluconeogenesis from amino acids due to heavy milk production may be a predisposing factor. Glucose metabolism is inextricably linked to that of protein and fats. In obesity (or lipodystrophy), the ability of adipose tissue to buffer the daily influx of nutrients is overwhelmed (or absent), interfering with insulin-mediated glucose disposal and leading to insulin resistance. Polyunsaturated fatty acids of the n-3 family play an important role in modulating insulin signalling and glucose uptake by peripheral tissue. The increasing demand on these fatty acids for milk fat synthesis towards late lactation may result in deficiency in the lactating female, thus impairing glucose disposal. It is suggested that the underlying cause of mink nursing sickness is the development of acquired insulin resistance with 3 contributing key elements: obesity (or lipodystrophy), n-3 fatty acid deficiency, and high protein oxidation rate. It is recommended that mink breeder females be kept in moderate body condition during fall and winter to avoid fattening or emaciation. A dietary n-3 fatty acid supplement during the lactation period may be beneficial for improved glycemic control. Lowering of dietary protein reduces (oxidative) stress and improves water balance in the nursing females and may, therefore, prevent the development and help in the management of nursing sickness. It is also surmised that other, thus far unexplained, metabolic disorders seen in male and female mink may be related to acquired insulin resistance.
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PMID:Nursing sickness in the mink--a metabolic mystery or a familiar foe? 1288 20

In 1980, 1700 people died during a prolonged heat wave in a region under-prepared for heat illness prevention. Dramatically underreported, heat-related pathology contributes to significant morbidity as well as occasional mortality in athletic, elderly, paediatric and disabled populations. Among US high school athletes, heat illness is the third leading cause of death. Significant risk factors for heat illness include dehydration, hot and humid climate, obesity, low physical fitness, lack of acclimatisation, previous history of heat stroke, sleep deprivation, medications (especially diuretics or antidepressants), sweat gland dysfunction, and upper respiratory or gastrointestinal illness. Many of these risk factors can be addressed with education and awareness of patients at risk. Dehydration, with fluid loss occasionally as high as 6-10% of bodyweight, appears to be one of the most common risk factors for heat illness in patients exercising in the heat. Core body temperature has been shown to rise an additional 0.15-0.2 degrees C for every 1% of bodyweight lost to dehydration during exercise. Identifying athletes at risk, limiting environmental exposure, and monitoring closely for signs and symptoms are all important components of preventing heat illness. However, monitoring hydration status and early intervention may be the most important factors in preventing severe heat illness.
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PMID:Heat illness in athletes: the dangerous combination of heat, humidity and exercise. 1471 36

Galanin-like peptide (GALP) is a 60-amino-acid peptide with structural similarities to galanin and a high affinity for galanin receptors. GALP is expressed by a discrete population of neurons in the arcuate nucleus (ARC) and median eminence of the hypothalamus of several species, including the rat. GALP neurons express leptin receptors and GALP mRNA levels are decreased slightly in fasted rats and stimulated significantly by acute leptin treatment in combination with fasting. In studies to further explore the leptin dependence of GALP expression, we examined GALP mRNA levels in the hypothalamus of obese Zucker and streptozotocin-induced diabetic (STZ-DM) rats. In leptin receptor-deficient obese Zucker rats, with 75% higher body weight than lean littermates, GALP mRNA levels in the ARC were decreased by 75%, while neuropeptide Y (NPY) mRNA levels were increased 7-fold (n = 5, p < 0.001), consistent with earlier reports. In hypoleptinemic diabetic rats with 4.5-fold higher blood glucose and 15% lower body weight than controls, GALP mRNA levels in the ARC were decreased by 90%, while NPY mRNA levels were increased 9-fold (n = 5, p < 0.001). GALP is also expressed by pituicytes in the neural lobe of the rat pituitary gland and GALP expression is increased by osmotic stimulation such as dehydration and salt loading. Thus, in STZ-DM rats that are in a hyperosmotic state with elevated plasma vasopressin levels, GALP mRNA levels were increased by approximately 20-fold in the neural lobe relative to control (n = 4, p < 0.001). The current findings are consistent with a strong tonic influence of leptin receptor signalling on hypothalamic GALP expression under normal conditions, and possible abnormalities in GALP neuronal signalling and their putative targets, thyrotropin-releasing hormone and gonadotropin hormone-releasing hormone neurons, under pathophysiological conditions such as diabetes and obesity. Our data in STZ-DM rats also clearly demonstrate that GALP gene expression is differentially regulated in neurons and pituicytes.
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PMID:Galanin-like peptide mRNA alterations in arcuate nucleus and neural lobe of streptozotocin-diabetic and obese zucker rats. Further evidence for leptin-dependent and independent regulation. 1525 10

Air passenger miles will likely double by year 2020. The altered and restrictive environment in an airliner cabin can influence haematological homeostasis in passengers and crew. Flight-related deep venous thromboemboli (DVT) have been associated with at least 577 deaths on 42 of 120 airlines from 1977 to 1984 (25 deaths/million departures), whereas many such cases go unreported. However, there are four major factors that could influence formation of possible flight-induced DVT: sleeping accommodations (via sitting immobilisation); travellers' medical history (via tissue injury); cabin environmental factors (via lower partial pressure of oxygen and lower relative humidity); and the more encompassing chair-rest deconditioning (C-RD) syndrome. There is ample evidence that recent injury and surgery (especially in deconditioned hospitalised patients) facilitate thrombophlebitis and formation of DVT that may be exacerbated by the immobilisation of prolonged air travel. In the healthy flying population, immobilisation factors associated with prolonged (>5 hours) C-RD such as total body dehydration, hypovolaemia and increased blood viscosity, and reduced venous blood flow (pooling) in the legs may facilitate formation of DVT. However, data from at least four case-controlled epidemiological studies did not confirm a direct causative relationship between air travel and DVT, but factors such as a history of vascular thromboemboli, venous insufficiency, chronic heart failure, obesity, immobile standing position, more than three pregnancies, infectious disease, long-distance travel, muscular trauma and violent physical effort were significantly more frequent in DVT patients than in controls. Thus, there is no clear, direct evidence yet that prolonged sitting in airliner seats, or prolonged experimental chair-rest or bed-rest deconditioning treatments cause DVT in healthy people.
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PMID:Airline chair-rest deconditioning: induction of immobilisation thromboemboli? 1545 46


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