Urinary 1-methylhistidine is a marker of meat consumption in Black and in White California Seventh-day Adventists.

Meat consumption predicts risk of several chronic diseases. The authors validate the accuracy of meat consumption reported by food frequency questionnaires and the mean of eight 24-hour recalls, using urinary methylhistidine excretion, in 55 Black and 71 White Adventist subjects in Los Angeles and San Diego, California, in 1994-1997. 1-Methylhistidine excretion predicts vegetarian status in Black (p = 0.02) and in White (p = 0.005) subjects. Spearman's correlation coefficients between 1-methylhistidine and estimated meat consumption were usually between 0.4 and 0.6 for both food frequency questionnaires and 24-hour recall data. This is despite the chance collection of dietary recalls and urines from omnivores on meatless days.

Dietary intake and biochemical, hematologic, and immune status of vegans compared with nonvegetarians.

Dietary and nutritional status of individuals habitually consuming a vegan diet was evaluated by biochemical, hematologic, and immunologic measures in comparison with a nonvegetarian group. On the basis of 4-d dietary records, the intake of female and male vegans tended to be lower in fat, saturated fat, monounsaturated fat, and cholesterol and higher in dietary fiber than that of vegetarians. With computed food and supplement intakes, vegan diets provided significantly higher amounts of ascorbate, folate, magnesium, copper, and manganese in both female and male participants. The body mass index (BMI; in kg/m(2)) of the vegans was significantly lower than that of the nonvegetarians and 9 of the 25 vegans had a BMI <19. Serum ferritin concentrations were significantly lower in vegan men but iron and zinc status did not differ between the sexes. Mean serum vitamin B-12 and methylmalonic acid concentrations did not differ; however, 10 of the 25 vegans showed a vitamin B-12 deficit manifested by macrocytosis, circulating vitamin B-12 concentrations <150 pmol/L, or serum methylmalonic acid >376 nmol/L. Vegans had significantly lower leukocyte, lymphocyte, and platelet counts and lower concentrations of complement factor 3 and blood urea nitrogen but higher serum albumin concentrations. Vegans did not differ from nonvegetarians in functional immunocompetence assessed as mitogen stimulation or natural killer cell cytotoxic activity.

Determination of free and total carnitine with a random-access chemistry analyzer.

Carnitine deficiency presents as a major problem in fatty acid oxidation. The use of a plasma carnitine assay can rapidly help to describe this deficiency. The method we describe here requires two simple steps of sample preparation, followed by automated analysis with the Beckman Synchron CX4 random-access chemistry analyzer. The goal of this method development was to reduce the cost of analysis and to allow a greater number of laboratories to perform this assay on demand within 1 h for both free and total carnitine. The method has a linearity of 0-150 micromol/L and a detection limit of 5 micromol/L. The inter- and intraday CVs are <20%. The method agreed closely with both the widely used RIA and spectrophotometric methods.

On the trail of potassium in heat injury.

In both classical and exertional heatstroke and in various animal models of human heat injury, clinical manifestations have included observations of normokalemia, hyperkalemia, and hypokalemia. This review attempts to address these observations as well as the role of potassium and potassium depletion in heat injury with an emphasis on the integration of information from the level of transmembrane potassium transport mechanisms to systems physiology. Under moderate conditions of passive heat exposure or exercise in the heat, the adaptive capacity of the Na-K pump (Na+-K+ ATPase activity) and cotransport mechanisms can ordinarily accommodate the attendant increased efflux of intracellular K+ and influx of extracellular Na+ to maintain ionic equilibrium. Several factors affecting transmembrane K+ kinetics include protracted K+ deficiency, extreme hyperthermia, dehydration, and excessive exertion. These could elicit reduced membrane potentials and conductance, futile cycling of the Na-K pump with concomitant energy depletion and greatly increased metabolic heat production, reduced arteriolar vasodilation, altered neurotransmitter release, or cell swelling, each of which could contribute to the pathophysiology of heat injury. This review represents a preliminary attempt to link transmembrane K+ pathophysiology with clinical heat injury.

American College of Sports Medicine position stand. Heat and cold illnesses during distance running.

Many recreational and elite runners participate in distance races each year. When these events are conducted in hot or cold conditions, the risk of environmental illness increases. However, exertional hyperthermia, hypothermia, dehydration, and other related problems may be minimized with pre-event education and preparation. This position stand provides recommendations for the medical director and other race officials in the following areas: scheduling; organizing personnel, facilities, supplies, equipment, and communication; providing competitor education; measuring environmental stress; providing fluids; and avoiding potential legal liabilities. This document also describes the predisposing conditions, recognition, and treatment of the four most common environmental illnesses: heat exhaustion, heatstroke, hypothermia, and frostbite. The objectives of this position stand are: 1) To educate distance running event officials and participants about the most common forms of environmental illness including predisposing conditions, warning signs, susceptibility, and incidence reduction. 2) To advise race officials of their legal responsibilities and potential liability with regard to event safety and injury prevention. 3) To recommend that race officials consult local weather archives and plan events at times likely to be of low environmental stress to minimize detrimental effects on participants. 4) To encourage race officials to warn participants about environmental stress on race day and its implications for heat and cold illness. 5) To inform race officials of preventive actions that may reduce debilitation and environmental illness. 6) To describe the personnel, equipment, and supplies necessary to reduce and treat cases of collapse and environmental illness.

Responses to moderate and low sodium diets during exercise-heat acclimation.

This investigation examined whether low sodium (Na+) (LNA; 68 mEq Na+.d-1) or moderate Na+ (MNA; 137 mEq Na+.d-1) intake allowed humans to maintain health, exercise, and physiologic function during 10 days of prolonged exercise-heat acclimation (HA). Seventeen volunteers, ages 19 to 21, consumed either LNA (n = 8) or MNA (n = 9) during HA (41 degrees C, 21% RH; treadmill walking for 30 min.h-1, 8 h.d-1 at 5.6 km.h-1, 5% grade), which resulted in significantly reduced heart rate, rectal temperature, and urine Na+ for both groups. There were few between-diet differences in any variables measured. Mean plasma volume in LNA expanded significantly less than in MNA by Days 11 and 15, but reached the MNA level on Day 17 (+12.3 vs. +12.4%). The absence of heat illness, the presence of normal physiologic responses, and the total distance walked indicated successful and similar HA with both levels of dietary Na+.

Symptomatic hyponatremia during prolonged exercise in heat.

Although hyponatremia (HN) has been reported among endurance athletes, its etiology often remains uncertain and of great interest to clinicians and physiologists. This case report presents physiologic evidence regarding the etiology and development of HN during exercise in the heat. A 21-yr-old male volunteer (K.G.) unexpectedly experienced symptomatic HN during a research investigation that involved controlled sodium (Na+) intake (137 mEq Na+.d-1 for 7d) and exercise-heat acclimation (41 degrees C; 30 min.h-1, 8 h.d-1 for 10 d). Fluid balance, physiologic variables, and hematologic/hormone data were measured before and after the HN episode, with similar measurements recorded for nine unaffected volunteers. The results indicated: 1) HN was verified in K.G. (plasma Na+ < 130 mEq.l-1) after only 4 h of mild, intermittent exercise in heat; 2) K.G.'s heart rate, rectal temperature, blood pressure, and Na+ losses in sweat and urine were < or = control subjects at all times; 3) between hours 4-7, an inappropriately large release of vasopressin coincided with a decrease of urine volume to 0 ml.h-1. It was concluded that a large intake (10.3 l.7h-1) and retention (2.77 l.7h-1) of water and a "low normal" initial plasma Na+ (134 mEq.l-1) were primary factors in the development of HN in K.G., whereas Na+ losses in sweat and urine were normal and served only to exacerbate HN.

Thyroid stimulating hormone and prolactin responses to thyrotropin releasing hormone in nondepressed alcoholic inpatients.

Thyroid stimulating hormone (TSH) and prolactin (PRL) responses to thyrotropin releasing hormone (TRH) stimulation are sometimes blunted in alcoholic subjects; however, the mechanisms involved in these phenomena have not been established. We hypothesized that elevations in free thyroid concentrations might be related to these abnormal responses and then tested that hypothesis in a sample of nondepressed alcoholic inpatients (n = 21). Four alcoholic patients had delta max TSH responses that were < 7 mIU/l; three had PRL responses at or below 8 micrograms/l. Baseline TSH was the only significant predictor of peak TSH; however, free thyroxine (FT4) and baseline TSH both were significant predictors of peak PRL. The average baseline FT4 concentration in alcoholic patients was significantly higher than that in healthy control subjects (n = 10). Our data, thus, suggest that small elevations of FT4 play a role in the inhibition of TSH and PRL responses to TRH among nondepressed, abstinent alcoholic patients.

Elevated plasma glucagon in amyotrophic lateral sclerosis.

This study shown an abnormality in glucagon levels that may explain the glucose intolerance, abnormal insulin reactions, and abnormal plasma amino acid levels seen in amyotrophic lateral sclerosis (ALS). We randomly administered two test meals, differing only in protein source (soy versus casein) at least 1 week apart and measured fasting and postprandial bloods for glucagon, insulin, and glucose levels in 11 ALS patients. With the soy test meal, glucagon levels were elevated in all ALS patients compared with controls: at fasting (237 +/- 111 versus 108 +/- 46 pg/ml, p less than 0.01) and 1/2 hour (389 +/- 94 versus 133 +/- 68 pg/ml, p less than 0.001), and 2 hours postprandial (379 +/- 75 versus 108 +/- 53 pg/ml, p less than 0.001). Glucagon levels after the casein test meal were also significantly elevated. Insulin was elevated by both test meals. Casein produced significant glucose intolerance.

Shared neuroendocrine patterns of post-traumatic stress disorder and alexithymia.

High norepinephrine/cortisol ratios have been shown to be useful indicators of post-traumatic stress disorder (PTSD). Alexithymia can result from overwhelming stress; thus, we hypothesized that sympathetic-adrenal medullary/hypothalamic-pituitary adrenal ratios would be positively associated with alexithymia severity. In the present study, we correlated 3-methoxy-4-hydroxyphenylethylene glycol (MHPG)/adrenocorticotropic hormone (ACTH) and MHPG/cortisol ratios with self-report Toronto Alexithymia Scale (TAS) scores in a group (n = 17) of nondepressed, formerly alcohol-dependent men. The correlations between the respective ratios and TAS scores were 0.515 (p = 0.034) and 0.561 (p = 0.019). We suggest that increasing degrees of alexithymia are accompanied by an increasing separation of these two endocrine systems and then speculate that this dissociation has an anatomical basis in the lateralization of emotions.

Fluid-electrolyte losses in uniforms during prolonged exercise at 30 degrees C.

The effects of several uniform configurations on fluid and electrolyte losses in a hot environment (30 degrees C db, 18 degrees C wb) were studied in 15 healthy males, during 6 h of intermittent treadmill exercise (1.56 m.s-1, 0% grade, 50 min.h-1, 28 km total distance). The uniforms were: the temperate battle dress uniform (BDU), two variants (C and F) of full military oriented protective posture (MOPP IV), and MOPP IV with no mask or hood (M). Sweat rate, urine volume, electrolyte losses (Na+, Cl-, K+, Mg++, Ca++) in sweat and urine, rectal temperature, mean skin temperature, heart rate, and temperature/humidity inside uniforms were measured. Observations indicated that both MOPP IV configurations (C and F) resulted in significantly greater (p. less than 0.05) fluid losses and physiological strain than BDU and M. However, there were no between-uniform differences in the total loss of any electrolyte. Total body fluid losses (kg.6h-1) and electrolyte losses in sweat (mEq.6h-1) were consistently greater than in urine. It was concluded that 6 h of exercise in uniforms at 30 degrees C can result in losses of Na+ and Ca++ which exceed the normal daily intake of these electrolytes. Supplementation of fluid, Na+, and Ca++ appears to be warranted when scenarios require 6 h or more of uniformed exposure to heat.

Physostigmine: dose-response effects on endurance and thermoregulation during exercise.

We previously reported that the administration of 200 micrograms/kg of physostigmine (PH) to rats exercising on a treadmill resulted in decrements in both endurance (decreased running time to exhaustion) and thermoregulation. However, it was necessary to determine the dose-response effects of PH administration before PH-treated exercising rats could be used as a model with which to examine the relative anticholinergic potency of drugs. In the present work saline, 50, 100, or 200 micrograms/kg of physostigmine salicylate (0%, 40%, 50%, and 60% whole blood cholinesterase inhibition) was administered to rats (N = 12/group) prior to treadmill exercise (26 degrees C, 50% rh, 11 m/min, 6 degrees incline). The saline control group ran for 67 +/- 6 min (mean +/- SE) with a rate of rise of core temperature of 0.051 +/- 0.007 degrees C/min. The run times declined (80%, 64% and 48% of control) as rate of rise of core temperature increased (116%, 180%, and 214% of control) in a dose-dependent manner (50, 100, 200 micrograms/kg PH). Cholinergic symptoms such as salivation, tremors, and defecation were also affected in a dose-dependent manner by PH administration. Since cholinergic symptoms, thermoregulatory effects, and endurance decrements all vary in a dose-dependent manner with physostigmine administration, the exercising rat represents a useful model for examining the relative potency of cholinergic therapies.

Plasma amino acids and the insulin/glucagon ratio as an explanation for the dietary protein modulation of atherosclerosis.

The amino acid composition of the diet influences the postprandial levels of plasma amino acids along with the hormones insulin and glucagon in humans fed single test meals identical in composition except for protein source. Soy protein (hypocholesterolemic), vs. casein (hypercholesterolemic), contains a higher amount of arginine and glycine and induces an increase in postprandial arginine and glycine. Soy protein induces a low postprandial insulin/glucagon ratio in both hypercholesterolemic and normocholesterolemic subjects. Casein induces a high postprandial insulin/glucagon ratio among hypercholesterolemic subjects. Amino acids such as arginine and glycine are associated with a decrease, while lysine and branched-chain amino acids are associated with increased serum cholesterol levels. Our data are consistent with the hypothesis that the control of cholesterol by insulin and glucagon is regulated by dietary and plasma amino acids. From this hypothesis the insulin/glucagon ratio is proposed as an early metabolic index of the effect of dietary proteins on serum cholesterol levels, a risk factor and a common mechanism through which dietary and lifestyle factors influence cardiovascular disease.

Plasma amino acids and the insulin/glucagon ratio as an explanation for the dietary protein modulation of atherosclerosis.

The amino acid composition of the diet influences the postprandial levels of plasma amino acids along with the hormones insulin and glucagon in humans fed single test meals identical in composition except for protein source. Soy protein (hypocholesterolemic), versus casein (hypercholesterolemic), contains a higher amount of arginine and glycine and induces an increase in postprandial arginine and glycine. Soy protein induces a low postprandial insulin/glucagon ratio in both hypercholesterolemic and normocholesterolemic subjects. Casein induces a high postprandial insulin/glucagon ration among hypercholesterolemic subjects. Amino acids such as arginine and glycine are associated with a decrease, while lysine and branched-chain amino acids are associated with increased serum cholesterol levels. Our data are consistent with the hypothesis that the control of cholesterol by insulin and glucagon is regulated by dietary and plasma amino acids. From this hypothesis the insulin/glucagon ratio is proposed as an early metabolic index of the effect of dietary proteins on serum cholesterol levels, a risk factor and a common mechanism through which dietary and lifestyle factors influence cardiovascular disease.

Prediction of the exercise-heat tolerance of soldiers wearing protective overgarments.

The purpose of this investigation was to see whether subject characteristics and physiologic measurements predicted exercise-heat tolerance (EHT) and voluntary tolerance time in young soldiers. A total of 18 unacclimatized males attempted six 50-min periods of treadmill walking (4.0 km.h-1, 0% grade, 33 degrees C db, 20% rh) while wearing protective overgarments. Two post hoc groups of soldiers were defined: high EHT (H) and low EHT (L), having mean (+/- S.E.) tolerance times of 360 +/- 0 and 222 +/- 12 min, respectively. Significant (p less than 0.05) H vs. L differences were observed in pretrial body mass, percent fat, and mass-to-surface area ratio (M/SA), as well as 170 min HR, Tsk and heat storage. The first three of these factors indicated that preexercise anthropomorphic characteristics may be used to distinguish H from L. The HR and Tsk differences were interpreted to mean that L experienced greater cardiovascular strain in protective overgarments because of a higher Tsk, which resulted in increased pooling of blood in cutaneous vessels, decreased cardiac filling pressure, and increased fatigue. Because HR variables were the strongest correlates of exercise tolerance time (r2 = 0.60 for HR at 170 min, r2 = 0.83 for time to reach HR of 160 beats.min-1) a novel HR monitoring technique was proposed which uses a wrist-mounted cardiotachometer to predict tolerance time.

Mass-to-surface area index in a large cohort.

Many biological and anthropological investigations have described the role between mass-to-surface area index (M/SA) and heat tolerance. No large M/SA database exists that can be used as a reference standard to interpret previous or future M/SA studies. This report presents the M/SA data of a large military cohort (1,170 males aged 17-54 years, 305 females aged 17-40 years). The effects of gender, ethnic group, and age on the distribution of M/SA, as well as the relationship between M/SA and other physical characteristics, were described. It was observed that the increases of M/SA with increasing age (over the 17-75 years category) were not significant. All descriptive characteristics (including M/SA) were different (P less than .001) between males and females. M/SA was not statistically different between ethnic groups among both males and females. These data may be utilized to compare the M/SA values of U.S. citizens to those of other ethnic groups and to identify those laborers or athletes who possess the greatest theoretical risk of heat intolerance.