Retrospective study of urinalysis for dl-amphetamine and dl-methamphetamine analysis under current Department of Defense guidelines.

Under current Department of Defense (DOD) directive, the laboratories certified to conduct urinalyis testing in support of the DOD Drug Deterrence Program are required to conduct dl-isomer analysis on all specimens that confirm at a concentration greater than 500 ng/mL methamphetamine (METH). Although the same cutoff concentration is required for amphetamine (AMP) reporting, there is no requirement for dl-isomer analysis of AMP-positive specimens. Of the 894,823 specimens screened by the Army Drug Testing Laboratory at Ft. Meade, MD during a 19-month period, 339 confirmed positive for METH. From this positive population, seven specimens failed to confirm at or above the DOD cutoff of > 20% d-isomer. One of the seven specimens contained 534 ng/mL l-AMP and was reported positive for AMP. Although 100% of the AMP was the l-isomer, under current DOD directive, this information was not passed along to the Medical Review Officers (MRO) to assist them during the interview process. Although this situation appears to be a rare event, consideration should be given to requiring dl-isomer analysis of AMP-positive specimens and forwarding this information to the MRO.

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.

Physical performance and metabolic recovery among lean, healthy men following a prolonged energy deficit.

Previous studies have demonstrated that full recovery from weight loss may take months or years. The present investigation examined short-term recovery (5 wks "post") of physical performance (muscular strength, muscular power, vertical jump), body composition, metabolic hormones (testosterone, luteinizing hormone, sex hormone binding globulin, insulin-like growth factor-1, triiodothyronine, thyroxine, thyroid binding globulin, and thyroid-stimulating hormone) and metabolic markers (transferrin, ferritin, prealbumin, glycerol, nonesterified fatty acids, high-density lipoproteins, and lactate) in 10 healthy young men after an 8-week Army course with an energy deficit (1000 kcal/d) and loss of body mass (-12%). Subjects ate ad libitum after the course ended ("post"). Body composition was determined by dual-energy X-ray absorptiometry; strength from a simulated power clean, power from body mass and jump height, and metabolic hormones were measured in morning-fasted blood by radioimmunoassay. With the exception of transferrin and glycerol, all study parameters were significantly (p<.05) altered by the training course. At 5 weeks post fat-free mass along with all physical performance measures returned to initial levels; however, fat mass had significantly (p<.05) increased over initial levels. Also, with the exception of lactate, all measured hormones and markers were close to initial levels and within normal ranges. Reported complications during recovery included sleep irregularities, diarrhea, loss of motivation and feelings of fatigue. While the long range effect of this energy deprivation experience is uncertain, these data do suggest that severe weight loss does not result in lasting alterations of the contractile and metabolic properties of skeletal muscle in young, lean, healthy men.

Carbohydrate-electrolyte solution effects on physical performance of military tasks.

BACKGROUND: Physical performance of military tasks can deteriorate during field training. HYPOTHESIS: Drinking a carbohydrate-electrolyte (CHO-E) beverage during military relevant training would improve fluid and caloric intake, and better sustain physical performance. METHODS: Some 27 volunteers restricted to approximately 2600 kcal.d-1 were randomly assigned to one of three groups: CHO-E, placebo, or water. Fluid intake was ad libitum. The volunteers completed 3 d of field training in hot humid conditions (30 degrees C, 60% rh). Training days 1 and 2 each included a 16-21 km march over hilly terrain, marksmanship training, and 2 h of rock climbing. Day 3 included a 14.5 km march followed by marksmanship tests, a timed rock climb and a 0.7 km uphill (21% grade) run. RESULTS: The CHO-E beverage provided an additional approximately 2800 kcal (p < 0.05) for the 3 d of training. There were no differences (ANOVA, p > 0.05) between the groups absolute or changes from pre-training values for fluid intake, body weight, climb time, run time, marksmanship, or mood. Those drinking CHO-E were, however, more likely to maintain uphill run performance after training (chi 2 = 7.2; p < 0.05) and more likely to maintain both uphill run and marksmanship ability (chi 2 = 17.2; p < 0.05). There was also an inverse relationship between caloric intake and deterioration of uphill run performance (r = -0.75; p < 0.05). CONCLUSIONS: Persons drinking CHO-E or practicing good food discipline are more likely to sustain physical performance than those eating only a portion of their food. CHO-E provides an accessible source of calories which can be advantageous when limited food is available or inadaquate food consumption is likely.

Effects of food restriction in military training on T-lymphocyte responses.

In a stress model which included food restriction, we examined the effects of physically rigorous military training and increased caloric intake on T-lymphocyte responses and lymphocyte subsets. T-lymphocyte proliferation and release of soluble receptor for interleukin-2 (slL-2R) in vitro were measured in two separate training classes of male U.S. Army ranger course (RC) trainees at the start and during the RC. Trainees in group 1 (n = 55) and 2(n = 50), respectively, had mean (+/- SD) energy intakes of 11.8 +/- 7.0 and 13.6 +/- 6.7 MJ/d, averaged total daily energy expenditures of 16.7 and 17.6 MJ/d, and experienced body weight losses of 15.]% and 12.6%. Both groups showed decreases T-lymphocyte responses in vitro: proliferation to phytohemagglutinin (PHA) and tetanus toxoid (TT), and released slL-2R to PHA. Group 2 with an intended 15% increase in energy during the RC over group 1 showed 22% and 26% less severe suppressions of T-lymphocyte proliferation and released slL-2R, respectively, in vitro. Group 2 also showed that short-term (9 days) removal of the food restriction stressor allowed for corrected body weight, total lymphocyte and T-lymphocyte subset counts but not suppressed T-lymphocyte responses in vitro. These results demonstrate that soldiers in physically rigorous military training are at risk of suppressed T-lymphocyte immunocompetence, and this is greater if they also experience inadequate energy intake.

Use of bioelectrical impedance analysis measurements as predictors of physical performance.

Through its association with fat-free mass (FFM), bioelectrical impedance analysis (BIA) offers an alternative to physical performance testing. We examined the relations between stature2/resistance (S2/R), FFM, and muscular strength in data from three studies of young military men and women. Resistance was measured at 50 kHz by using the conventional tetrapolar electrode method. FFM was based on skinfold thicknesses, and estimated with the regression equations of Durnin and Womersley. Strength was measured as a one-repetition maximum on an incremental lift test (IL1RM), which is widely used by the military services to predict overall body strength. Although there was an association between IL1RM and S2/R in each of these studies (correlations ranged from 0.35 to 0.53), correlations were strongest between FFM and S2/R (R = 0.53 to 0.85), indicating that BIA and FFM derived from skinfold thicknesses are better correlated with each other than are the relations of either of these with physical performance. Modest increases in FFM and strength in one 8-wk training study correlated with S2/R; however, large decreases in FFM and strength in another study (with weight losses of 10 kg in 8 wk) were not reflected by changes in S2/R. Thus, BIA is not particularly useful for performance prediction despite its moderate relation to FFM. BIA is especially problematic with large changes in body composition, for which there are apparent deviations in hydration status; expedient methods such as skinfold predictions will be more resistant to such effects.

Regional fat placement in physically fit males and changes with weight loss.

The abdomen is the principal site of fat deposition in men, and because abdominal fat is readily mobilized during exercise, the relative proportion of fat in the abdominal site may negatively correlate with the amount of regular physical activity, and even with physical fitness. This study presents data for regional fatness in 165 fit young men (U.S. Army Ranger candidates; initial body fat = 14.7 +/- 4.7%) assessed by dual-energy x-ray absorptiometry (DEXA), and for relative changes occurring following a 13% weight loss produced by a 1000 kcal.d-1 energy deficit over 8 wk. Fat-free mass was constant across quintiles of percent body fat; only fat mass was different (16.2 +/- 2.2 kg and 6.0 +/- 1.4 kg at upper and lower quintiles, respectively). Truncal fat accounted for about 41% of total body fat in all quintiles; only the proportion of fat distributed to the arms was significantly higher in the fattest quintiles of men. Among a group of less intensely trained soldiers with the same average fatness as the highest quintile of Ranger students (20%), relative fat distribution to the trunk approached 50% of the total fat. Following weight loss, Ranger students lost half of the fat in all regions assessed (legs, arms, and trunk). The only significant association between regional losses and initial fatness was a greater proportion of fat lost from the arms in the fattest Rangers. These data suggest a "fit fat" distribution in active young men in which fat remains in the arms and legs until extreme weight loss occurs and the metabolically more active abdominal fat approaches depletion.

Kinetics of nitrogen oxide production following experimental thermal injury in rats.

Nitric oxide is biosynthesized from the amino acid L-arginine by the enzyme nitric oxide synthase. Nitric oxide is a vasodilator, a neurotransmitter, and may modulate immune function. The experiments presented here were performed to determine whether the synthesis of nitric oxide is increased following experimental burn injury in rats. After a 30% total body surface area burn in 300-g Lewis rats, the urinary output of nitrate, a stable metabolite of nitric oxide, was significantly increased for 8 days postburn compared with that in sham-burned control rats. The origin of the urinary nitrate from L-arginine was demonstrated by administering the stable isotope 15N2-guanido-arginine to burned and sham-burned rats and observing an immediate enrichment of 15N in nitrate. The amount of administered 15N recovered as 15NO3 was < 1% of the administered arginine isotope in both the burned and unburned rats; the recovery of the isotope increased tenfold over baseline recovery in burned rats. The arginine analog N-monomethyl-arginine, an inhibitor of the enzyme nitric oxide synthase, blocked the postburn rise in urinary NO3 output in burned rats, but did not completely inhibit the output of NO3 in burn wound-infected rats. Experimental burn injury in rats results in an increase in L-arginine-dependent nitric oxide production and urinary nitrate output.

A rabbit model of inhalation injury.

In the course of developing a model of inhalation injury, the relationship between the severity of pulmonary injury and specific techniques and doses of smoke exposure was examined in pairs of rabbits simultaneously exposed to smoke. In group I (5 pairs), one animal in each pair was exposed to smoke with a breath hold (BH) at the end of each exposure; the second animal received an exposure producing the same level of carboxyhemoglobin without BH. In group II (6 pairs), both animals were exposed to 25 units of smoke simultaneously, with BH. In group III (3 pairs), one animal received a 20-unit exposure and the other a 25-unit exposure, both with BH. In group IV, 9 animals received 25-unit exposures with BH and were observed for 4 days. Groups V and VI served as controls. Smoke exposure with BH regularly produced severe injury in terms of decreased PaO2 and histopathologic changes, while exposure without BH did not, despite high levels of carboxyhemoglobin after smoke inhalation. The mean differences in percent residual PaO2 (PaO2 at 48 hours x 100/pre-injury PaO2) and in extravascular lung water (EVLW) at 48 hours within pairs of animals receiving 25 units with BH were 12.3% +/- 5.33%, and 0.271 +/- 0.157 mL/g, respectively. Histologic findings such as necrotic tracheobronchitis with pseudomembrane were consistently present. No differences were observed between animals receiving exposure of 20 and 25 units. During the 4 days of observation, three animals in group IV died. PaO2 was lowest on the second day and rose thereafter in all surviving animals except in one that had massive pneumonia.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous determination of lactulose and mannitol in urine of burn patients by gas-liquid chromatography.

Ratios of lactulose/mannitol excretion in urine have been used to assess the extent of intestinal permeability in various disease and trauma conditions. Reported studies have used this technique to correlate altered gastrointestinal mucosal permeability to translocation of bacteria and endotoxin, leading to occult sepsis in burn patients. Enzymatic methods of analysis for urine concentrations of mannitol and lactulose were used in these studies. We have found that urine from patients with severe burns frequently contains compounds that interfere with the enzymatic methods. We describe using gas-liquid chromatography to determine mannitol and lactulose simultaneously in the urine of burn patients. To avoid the multiple peaks for the anomeric forms of the reducing sugars during precolumn trimethylsilyl derivatization, we converted the sugars to oximes before the silylation step. The method gave good recoveries of mannitol and lactulose added to burn patients' urine samples. Unlike the enzymatic methods, gas-liquid chromatography eliminates the effect of interfering compounds and allows for the simultaneous determination of both sugars in urine samples.

The interaction of burn injury and zinc nutriture as assessed by the humoral response to sheep red blood cells in a burn rat model.

Clinical and animal studies suggest that burn injury induces alterations in zinc metabolism. It also has been established that zinc nutriture can cause alterations in the immune response, but there is a paucity of information concerning the interrelationship between burn injury, zinc nutriture and the immune response. In the present study, rats were subjected to full skin thickness dorsal scald injuries covering 30 per cent of the total body surface and then maintained on sufficient or deficient zinc intake. The rats were immunized with sheep red blood cells (SRBC) on day 6 postburn and killed 4 days later. The spleens were excised and spleen lymphocytes isolated and used in a Jerne plaque assay to determine the number of plaque-forming cells (PFC). The burn/zinc-sufficient regimen significantly increased (P less than 0.01) the PFC response when compared to unburned zinc-sufficient or zinc-deficient control rats. Burned rats that were maintained on a zinc-deficient regimen showed a significant decrease (P less than 0.05) in PFC when compared to burned rats maintained on a zinc-sufficient regimen. This study indicates an interaction of zinc in the primary humoral immune response following thermal injury.

Electrophysiologic responses of human sural nerve to temperature.

The purpose of this study was to assess the conduction, specifically the latency and amplitude of the sensory nerve action potential (SNAP), of the sural nerve as a function of intraneural temperature of the leg. The electrophysiologic responses of the sural nerve were determined at different temperatures in 22 healthy adults. Distal sensory latency and amplitude of the sural SNAP was determined at 1 degree C intervals over a limb temperature range of 23 degrees to 40 degrees C. Limb temperature was monitored with a thermistor probe placed subcutaneously near the sural nerve. Ice bath soaks were used for cooling and infrared radiation for warming the limbs. An analysis of covariance was performed for the SNAP latencies and amplitudes to determine the effect of gender and leg (right or left) at each temperature level. No effect of gender or leg on neural conduction was detected in individual subjects. A regression analysis was then used on pooled data to determine the effect of temperature on sural SNAP latency and amplitude. An inverse linear change in the latency of sural SNAP was observed over the temperature ranges used. Mean latency increased 0.1 msec per 1 degree C increase in subcutaneous temperature. A direct relationship between amplitude of the SNAP and temperature was determined. Mean amplitude increased 0.3 muV per 1 degree C increase in subcutaneous temperature. The results of this study support previous reports, which state that SNAP latency is indirectly related to the intraneural temperature. Clinical electromyographers must monitor the temperature of the lower leg and foot whenever sensorineural conduction of the lower limbs is performed.

The effect of burn injury and zinc nutriture on fecal endogenous zinc, tissue zinc distribution, and T-lymphocyte subset distribution using a murine model.

The interrelationship among burn injury, zinc metabolism, and circulating T-lymphocyte distribution was studied using a rat model. Sixty Sprague-Dawley male rats were fed a zinc-deficient (less than 0.5 ppm) semipurified diet and given daily subcutaneous injections of 1 mg Zn/kg body wt for 14 days. On Day 15, 24 of the rats were subjected to a full-thickness dorsal scald injury of 30% of the total body surface. Half of the burned rats were continued on the zinc supplementation (BS) while the other half were maintained on the zinc-deficient (BD) regimen by injecting physiological saline. Feces and urine were collected for 10 days postburn and subsequently analyzed for zinc content. On Day 10 postburn all the rats were sacrificed. Zinc bound to cytosol proteins in hepatic and intestinal mucosal tissue was determined by gel column chromatography procedures and T-lymphocyte subset distributions were determined by flow cytometry. No significant difference (P less than 0.05) in total endogenous zinc excretion was seen among treatment groups. A dramatic increase was seen in zinc bound to a 12,000 mol wt protein in hepatic tissue from the BS group only. The only significant (P less than 0.05) change in T-lymphocyte populations was an increase in T-suppressor cells in the BD group.

Trace mineral supplementation of burn patients: a national survey.

Much research effort has been devoted to determination of caloric and protein requirements in burn patients. Although it is generally accepted that trace mineral requirements increase concomitantly with caloric and protein needs, little research has been conducted to document that assumption. Our survey was undertaken to assess current practice and identify research needs. One hundred ninety-six survey questionnaires were sent to burn units in North America. Forty percent (78) were returned. Ninety percent of respondents prescribe or recommend trace mineral supplements in their facilities. "Higher risk" was the single criterion most often mentioned as a basis for supplementation (54 [77%] of 70 respondents), with 49 of them indicating that they provide trace mineral supplements to patients receiving total parenteral nutrition support. Fifty-six respondents provided detailed information concerning trace mineral supplementation. Of that group, 88% prescribe zinc supplements, 75% prescribe iron supplements, and 26% prescribe chromium supplements. Thirteen percent supplement selenium. Less than 2% supplement molybdenum or vanadium and do so only when administering total parenteral nutrition. Many respondents expressed concern about the lack of guidelines for trace mineral supplementation in the burn patient, leading to the conclusion that further research in that area would benefit burn-injured patients and the health care providers who care for them.

Cadmium-induced suppression of the primary immune response and acute toxicity in mice: differential interaction of zinc.

Four groups of 6-week-old C3H mice were injected sc with either sterile saline, 2.8 mg Cd/kg body weight, 2.8 mg Zn/kg body weight, or 2.8 mg each of Cd and Zn/kg body weight. Forty-eight hours after the initial injection, all mice received a second dose of their respective treatments plus an iv injection of sheep red blood cells. On Days 2, 3, 4, and 5 postimmunization the mice were killed. Spleen cells were used in a hemolytic plaque-forming assay for the quantitation of the primary humoral response. Although the combined administration of zinc and cadmium completely prevented the fatal effects of the cadmium (0 vs 55% mortality), zinc failed to alleviate the cadmium-induced inhibition of the humoral response.