Biomedical subjects

J W Castellani

Publications and source records attributed to J W Castellani.

30 records · Page 2Linked to original sources

PubMed1998

Amnesia during cold water immersion: a case report.

This report describes a case of amnesia during a cold-water experiment. The volunteer was exposed three times in 1 day (120 min duration each time) to 20 degrees C water. During the third immersion, from min 95 to min 115, the subject experienced transient global amnesia for 20 min. The rectal temperature during this time was 35.6 degrees C. This single case demonstrates that memory loss in a young individual apparently can occur after cold-water exposure and at core temperatures above 35 degrees C.

Adult↗

PubMed1998

Immune deficits induced by strenuous exertion under adverse environmental conditions: manifestations and countermeasures.

A brief description is given of the various laboratory and clinical manifestations of immune suppression that arise when strenuous exertion must be carried out in the face of a negative energy balance, shifts of circadian rhythm, sleep deprivation, psychological stressors, and exposure to hostile environments (extremes of heat or cold, high or low ambient pressures, and hyper- or hypo-gravity conditions). From the operational viewpoint, immune suppression could impair both physical and mental performance by increasing susceptibility to opportunistic microorganisms. It is also likely to increase susceptibility to sepsis following trauma or extensive burns, and has occasionally predisposed to fatal myocarditis. The effects of such challenges are complex, in part because of interactions between the various stressors. It is thus important to investigate the impact and to devise appropriate countermeasures with the full physical and intellectual resources of a defense environmental research laboratory. Existing knowledge of the topic is reviewed, and suggestions are made for research that may lead to new and more effective countermeasures.

Energy Metabolism↗

PubMed1997

Effects of oral and intravenous rehydration on ratings of perceived exertion and thirst.

The purpose of this investigation was to compare the effects of oral and intravenous saline rehydration on differentiated ratings of perceived exertion (RPE) and thirst. Eight men underwent three randomly assigned rehydration treatments following a 2- to 4-h exercise-induced dehydration bout to reduce body weight by 4%. Treatments included 0.45% saline infusion (i.v.), 0.45% saline oral ingestion (ORAL), and no fluid (NF). Following rehydration and rest (2 h total), subjects walked at 50% VO2max for 90 min at 36 degrees C (EX). Central RPE during ORAL was lower (P < 0.05) than i.v. and NF throughout EX. Local RPE during NF was higher (P < 0.05) than i.v. and ORAL at minutes 20 and 40 of EX and overall RPE during NF was higher (P < 0.05) than ORAL at minutes 20 and 40 of EX. Significant correlations were found between overall RPE and mean skin temperature for i.v. (r = 0.72) and NF (r = 0.75), and between overall RPE and thirst ratings for i.v. (r = 0.70). Thirst ratings were not different among trials at postdehydration. Following rehydration, thirst was higher (P < 0.05) during NF than i.v. and ORAL and lower (P < 0.05) during ORAL than i.v. at all subsequent time points. Results suggest that oral rehydration is likely to elicit lower RPE and thirst ratings compared with intravenous rehydration.

Adult↗

PubMed1997

Bioimpedance spectroscopy technique: intra-, extracellular, and total body water.

The purpose of this study was to test the validity of a multiple frequency bioimpedance spectroscopy (BIS) technique that estimates extracellular fluid volume (ECV), intracellular fluid volume (ICV), and total body water (TBW). Thirteen healthy males (mean +/- SD: age, 23 +/- 3 yr; body mass, 80.6 +/- 14.7 kg) had their TBW and ECV measured by ingesting dilution tracers (7.27 g deuterium oxide, 1.70 g sodium bromide; blood samples at 0 and 4 h). ICV was calculated as TBW minus ECV. Impedance was measured (50-500 kHz) at rest, on a nonconducting surface, with a BIS analyzer. Electrode placement, posture, exercise, food/fluid intake, and ambient temperature were controlled. Dilution measures (TBW, 51.00 +/- 9.30; ECV, 19.88 +/- 3.14; ICV, 31.12 +/- 6.80 L) and BIS volumes (TBW, 50.03 +/- 7.67; ECV, 20.95 +/- 3.33; ICV, 29.04 +/- 4.51 L) were significantly different for ECV (P < 0.01) and ICV (P < 0.05); some individual differences were large. The correlation coefficients of dilution versus BIS volumes (r = 0.93 to 0.96) were significant at P < 0.0001; SEEs were: TBW, 2.23 L; ECV, 1.26 L; and ICV, 1.71 L. We concluded that BIS is valid for between-subject comparisons of body fluid compartments, is appropriate in clinical settings where change in ECV/ICV ratio is important, and should be used by comparing the required level of accuracy to the inherent technique error/variance.

Adult↗

PubMed1997

Intravenous vs. oral rehydration: effects on subsequent exercise-heat stress.

This study compared the influence of intravenous vs. oral rehydration after exercise-induced dehydration during a subsequent 90-min exercise bout. It was hypothesized that cardiovascular, thermoregulatory, and hormonal variables would be the same between intravenous and oral rehydration because of similar restoration of plasma volume (PV) and osmolality (Osmo). Eight non-heat-acclimated men received three experimental treatments (counterbalanced design) immediately after exercise-induced dehydration (33 degrees C) to -4% body weight loss. Treatments were intravenous 0.45% NaCl (iv; 25 ml/kg), no fluid (NF), and oral saline (Oral; 25 ml/kg). After rehydration and rest (2 h total), subjects walked at 50% maximal O2 consumption for up to 90 min at 36 degrees C. The following observations were made: 1) heart rate was higher (P < 0.05) in Oral vs. iv at minutes 45, 60, and 75 of exercise; 2) rectal temperature, sweat rate, percent change in PV, and change in plasma Osmo were similar between iv and Oral; 3) change in plasma norepinephrine decreased less (P < 0.05) in Oral compared with iv at minute 45; 4) changes in plasma adrenocorticotropic hormone and cortisol were similar between iv and Oral after exercise was initiated; and 5) exercise time was similar between iv (77.4 +/- 5.4 min) and Oral (84.2 +/- 2.3 min). These data suggest that after exercise-induced dehydration, iv and Oral were equally effective as rehydration treatments. Thermoregulation, change in adrenocorticotropic hormone, and change in cortisol were not different between iv and Oral after exercise began; this is likely due to similar percent change in PV and change in Osmo.

Adult↗

PubMed1997

Thermal and circulatory responses during exercise: effects of hypohydration, dehydration, and water intake.

This investigation examined the distinct and interactive effects of initial hydration state, exercise-induced dehydration, and water rehydration in a hot environment. On four occasions, 10 men performed a 90-min heat stress test (treadmill walking at 5.6 km/h, 5% grade, 33 degrees C, 56% relative humidity). These heat stress tests differed in pretest hydration [2 euhydrated (EU) and 2 hypohydrated (HY) trials] and water intake during exercise [2 water ad libitum (W) and 2 no water (NW) trials]. HY+NW indicated greater physiological strain than all other trials (P < 0.05-0.001) in heart rate, plasma osmolality (Posm), sweat sensitivity (g/degrees C.min), and rectal temperature. Unexpectedly, final HY+W and EU+W responses for rectal temperature, heart rate, and Posm were similar, despite the initial 3.9 +/- 0.2% hypohydration in HY+W. We concluded that differences in pretest Posm (295 +/- 7 and 287 +/- 5 mosmol/kg for HY+W and EU+W, respectively) resulted in greater water consumption (1.65 and 0.31 liter for HY+W and EU+W, respectively), no voluntary dehydration (0.9% body mass increase), and attenuated thermal and circulatory strain during HY+W.

Adult↗

PubMed1996

Plasma norepinephrine responses to cycle exercise in boys and men.

Previous reports have suggested that plasma norepinephrine levels during exercise, an indicator of sympathetic neurologic activity, may be less in children than in adults. This study investigated plasma norepinephrine values at rest, during two submaximal cycle exercise intensities, and at maximal exercise in 11 boys aged 10 to 12 years and 11 men aged 24 to 35 years. Blood specimens were drawn at average submaximal exercise intensities of 58.7% and 73.0% for the boys and 55.3% and 73.3% VO2max for the men. Weight-relative maximal aerobic power was similar in the two groups. No statistically-significant differences were observed in plasma norepinephrine values at rest or during submaximal and maximal exercise between the boys and men. Maximal levels were 1196 (326 SD) and 1385 (612 SD) pg.ml-1 for the boys and men, respectively (p > 0.05). These findings suggest that sympathetic influences during maximal and submaximal exercise are independent of biological maturation.

Adult↗

PubMed1995

Fluid-electrolyte balance associated with tennis match play in a hot environment.

Twenty (12 male and 8 female) tennis players from two Division I university tennis teams performed three days of round-robin tournament play (i.e., two singles tennis matches followed by one doubles match per day) in a hot environment (32.2 +/- 1.5 degrees C and 53.9 +/- 2.4% rh at 1200 hr), so that fluid-electrolyte balance could be evaluated. During singles play, body weight percentage changes were minimal and were similar for males and females (males -1.3 +/- 0.8%, females -0.7 +/- 0.8%). Estimated daily losses (mmol.day-1) of sweat sodium (Na+) and potassium (K+) (males, Na+ 158.7, K+ 31.3; females, Na+ 86.5, K+ 18.9) were met by the players' daily dietary intakes (mmol.day-1) of these electrolytes (males, Na+ 279.1 +/- 109.4, K+ 173.5 +/- 57.7; females, Na+ 178.9 +/- 68.9, K+ 116.1 +/- 37.5). Daily plasma volume and electrolyte (Na+, K+) levels were generally conserved, although, plasma [Na+] was lower (p < .05) on the morning of Day 4. This study indicated that these athletes generally maintained overall fluid-electrolyte balance, in response to playing multiple tennis matches on 3 successive days in a hot environment, without the occurrence of heat illness.

Adolescent↗

PubMed1995

Local cooling in wheelchair athletes during exercise-heat stress.

Wheelchair athletes with spinal cord injuries (WA) face challenges to thermal homeostasis, including reduced cutaneous vasoaction and sweat production. The purpose of this study was to evaluate the efficacy of local cooling to reduce heat strain in WA. Six elite, endurance-trained male WA (33 +/- 3 yr, 64 +/- 4 kg) performed three strenuous exercise tests in a hot-humid environment (32.9 +/- 0.1 degrees C, 75 +/- 3% RH) by pushing a racing chair on a stationary roller (30 min, 16.5 km.h-1, 704-766 W metabolic heat) while wearing shorts and socks. The three treatments involved an ice-packet vest (V) (0.14 m2 of skin surface), a refrigerated headpiece (H) (0.16 m2), or no cooling (C) (control). The vest and headpiece offered potential cooling of 388 W and 266 W. Mean body heat storage for trials V (117 +/- 26 W), H (117 +/- 22 W), and C (164 +/- 40 W) were statistically similar, partly because V (117 +/- 47 W) and H (75 +/- 59 W) cooled inefficiently (30 and 28%, respectively). Repeated measure ANOVA indicated no significant between-treatment differences (P > 0.05) for any variable in trials V, H, and C. We concluded that local cooling during V and H was ineffective because heat storage decreased, but was not prevented.

Adult↗

PubMed1994

Effects of hydration state on plasma testosterone, cortisol and catecholamine concentrations before and during mild exercise at elevated temperature.

This investigation examined the influence of pre-exercise hydration status, and water intake during low intensity exercise (5.6 km.h-1 at 5% gradient) in the heat (33 degrees C), on plasma testosterone (TEST), cortisol (CORT), adrenaline (A), and noradrenaline (NA) concentrations at baseline (BL), pre-exercise (PRE), and immediately (IP), 24 h (24 P), and 48 h postexercise (48 P). Ten active men participated in four experimental treatments. These treatments differed in pre-exercise hydration status [euhydrated or hypohydrated (HY, -3.8 (SD 0.7)% body mass)] and water intake during exercise (water ad libitum or no water intake during exercise, NW). There were no significant changes in TEST, CORT, or A concentrations with time (BL, PRE, IP, 24 P, and 48 P), or among treatments. However, significant increases from BL and PRE plasma NA concentrations were observed at IP during all four treatment conditions. In addition, HY+NW resulted in significantly higher plasma NA concentrations at IP compared to all other treatments. These results suggest that moderate levels of hypohydration during prolonged, low intensity exercise in the heat do not influence plasma TEST, CORT, or A concentrations. However, plasma NA appears to respond in a sensitive manner to these hydration and exercise stresses.

Adult↗

PubMed1994

Urinary indices of hydration status.

Athletes and researchers could benefit from a simple and universally accepted technique to determine whether humans are well-hydrated, euhydrated, or hypohydrated. Two laboratory studies (A, B) and one field study (C) were conducted to determine if urine color (Ucol) indicates hydration status accurately and to clarify the interchangeability of Ucol, urine osmolality (Uosm), and urine specific gravity (Usg) in research. Ucol, Uosm, and Usg were not significantly correlated with plasma osmolality, plasma sodium, or hematocrit. This suggested that these hematologic measurements are not as sensitive to mild hypohydration (between days) as the selected urinary indices are. When the data from A, B, and C were combined, Ucol was strongly correlated with Usg and Uosm. It was concluded that (a) Ucol may be used in athletic/industrial settings or field studies, where close estimates of Usg or Uosm are acceptable, but should not be utilized in laboratories where greater precision and accuracy are required, and (b) Uosm and Usg may be used interchangeably to determine hydration status.

Adult↗

PubMedDate not supplied

Cortisol and testosterone concentrations in wheelchair athletes during submaximal wheelchair ergometry.

It is yet unknown how upper body exercise combined with high ambient temperatures affects plasma testosterone and cortisol concentrations and furthermore, how these hormones respond to exercise in people suffering spinal cord injuries. The purpose of this study was to characterize plasma testosterone and cortisol responses to upper body exercise in wheelchair athletes (WA) compared to able-bodied individuals (AB) at two ambient temperatures. Four WA [mean age 36 (SEM 13) years, mean body mass 66.9 (SEM 11.8) kg, injury level T7-T11], matched with five AB [mean age 33.4 (SEM 8.9) years, mean body mass 72.5 (SEM 13.1) kg] exercised (cross-over design) for 20 min on a wheelchair ergometer (0.03 kg resistance.kg-1 body mass) at 25 degrees C and 32 degrees C. Blood samples were obtained before (PRE), at min 10 (MID), and min 20 (END) of exercise. No differences were found between results obtained at 25 degrees C and 32 degrees C for any physiological variable studied and therefore these data were combined. Pre-exercise testosterone concentration was lower (P < 0.05) in WA [18.3 (SEM 0.9) nmol.l-1] compared to AB [21.9 (SEM 3.6) nmol.l-1], and increased PRE to END only in WA. Cortisol concentrations were similar between groups before and during exercise, despite higher rectal temperatures in WA compared to AB, at MID [37.21 (SEM 0.14) and 37.02 (SEM 0.08) degrees C, respectively] and END [37.36 (SEM 0.16) and 37.19 (SEM 0.10) degrees C, respectively]. Plasma norepinephrine responses were similar between groups. In conclusion, there were no differences in plasma cortisol concentrations, which may have been due to the low relative exercise intensities employed. The greater exercise response in WA for plasma testosterone should be confirmed on a larger population. It could have been the result of the lower plasma testosterone concentrations at rest in our group.

Adult↗