Urinary catecholamine metabolites distinguish different types of sympathetic neuronal dysfunction in patients with orthostatic hypotension.

Urinary excretion rates of the major norepinephrine metabolites, 3-methoxy-4-hydroxymandelic acid, 3-methoxy-4-hydroxy-phenylglycol and normetanephrine, were determined in 12 normal subjects and 23 patients with neurogenic orthostatic hypotension due to either multiple system atrophy [Shy-Drager Dyndrome (MSA)] or idiopathic orthostatic hypotension (IOH). There were striking and parallel decreases in all catecholamine metabolites in IOH consistent with loss of peripheral sympathetic nerves. Patients with MSA excreted greater amounts of the deaminated metabolites than did the patients with IOH, but most excreted equally low amounts of normetanephrine. The disproportionate decrease in excretion of normetanephrine by patients with MSA is consistent with observations in experimental animals that O-methylation is the primary metabolic route for active released norepinephrine, whereas deamination is the predominant metabolic route for intraneuronal degradation of the catecholamine. The similar proportional decreases in all catecholamine metabolites in patients with IOH (who have no central nervous system deficit) indicates that brain norepinephrine is a source of only a small fraction of urinary norepinephrine metabolites, including 3-methoxy-4-hydroxy-phenylglycol.

Body fluid and hematologic adjustments during resting cold acclimation in rhesus monkey.

The purpose of this study was to examine body fluid adjustments during prolonged cold exposure in primates. Six male rhesus monkeys were acclimated for 35 days and 6 degrees C and 80% rh. Red cell mass, extracellular fluid volume, and total body water (TBW) were determined with 51Cr, 35SO4, and 3H2O, respectively, prior to and at various intervals during the cold stress. TBW was increased throughout the exposure, whereas changes in extravascular compartments had occurred within the 1st wk of cold exposure, after which they returned to control values. An increased concentration of blood constituents on day 1 was not accompanied by a decrease in cardiovascular volume. Blood volume and plasma volume in relation to TBW were significantly increased on day 3 and remained increased during the remainder of the exposure. These cardiovascular volume changes were accompanied by a significant hemodilution on day 3 and a gradual return to control values. An increased plasma osmolality and expansion of the erythrocytes (decrease in mean corpuscular hemoglobin concentration) were observed throughout the cold stress. These data suggest that the rhesus monkey may be an adequate primate model for studies of body fluid adjustments, especially during prolonged cold exposure, in primates in general, including the human.

Body fluid and hematologic adjustments during resting heat acclimation in rhesus monkey.

The purpose of this study was to examine body fluid adjustments during prolonged resting heat exposure in primates. Rhesus monkeys were acclimated for 35 days at 35 degrees C and 30% rh. Red cell mass, extracellular fluid volume (ECF), and total body water (TBW) were determined with 51Cr, 35SO4, and 3H2O, respectively, prior to and at intervals during heat exposure. Heat acclimation was characterized by a fluid shift from the interstitial compartment. In relation to TBW, interstitial fluid volume and ECF decreased 10.3 and 8.3%, respectively, while plasma volume (PV) and intracellular fluid were increased an average of 5.8 and 3.8%. TBW increased 4.8% during heat exposure. Hematocrit and hemoglobin decreased significantly on day 3 (7.9 and 6.5%) followed by a return toward control values. PV in relation to TBW remained elevated throughout the exposure. An increased drinking (25.0%) was associated with a decrease in caloric intake (30.7%) during heat acclimation. This study has provided a complete body fluid compartment analysis during resting heat acclimation in the rhesus monkey. Our results are consistent with the hypothesis that heat acclimation in primates is characterized by a protein and fluid shift from the interstitial fluid compartment to the cardiovascular system and to the intracellular compartment.

Cardiac output during rest and exercise in desert heat.

Cardiac output and stroke volume were measured in two environments and at metabolic rates ranging from rest to the maximum rate that could be sustained for 25 minutes. One environment was indoors at about 23 degrees C, the other outdoors in desert sunshine and low water vapor pressure. The age range of the one female and four of the male subjects was from 19 to 40; the fifth male subject was 85 years old. Cardiac output was the same in the two environments; stroke volume was less at higher metabolic rates in the heat. The cardiac output for the old man was about one-tenth less and stroke volume about 20 ml less than that observed for the same work 50 years earlier.

Physiological adjustments of young men to five-hour desert walks.

Seven young men undertook a desert walk of 30 km at a rate of 100 m/min. Six finished; the seventh stopped after 24 km. Each satisfied his thirst with cool tap water each hour. Periodic observations included metabolic rate, blood pressure, heart rate, rectal and skin temperature, body weight, and volume of water drunk. Hand sweat was collected each hour and body sweat residues on the skin were collected at the end of the walk. Subjective reports revealed portents of breakdown: aching muscles, painful joints, hot or blistered feet, hunger, and boredom. Cardiovascular adjustment and temperature regulation maintained tolerable conditions. The volumes of water evaporated by the 5-h walkers were about the same. Wet bulb temperatures were below 25 degrees C; all sweat evaporated and was available for temperature regulation. The volume of water drawn from body reserves was closely correlated with concentration of chloride in body sweat; the volume of water that satisfied thirst maintained osmotic pressure.