Body Size Influences Stingless Bee (Hymenoptera: Apidae) Communities Across a Range of Deforestation Levels in Rondônia, Brazil

Developments in understanding bee responses to habitat loss indicate that body size is a trait with important consequences for conservation. Stingless bees (Hymenoptera, Apidae, Meliponini) are a diverse group of eusocial bees providing pollination services in tropical landscapes, exhibiting a large range in body size across species. We tested the effects of deforestation on the body sizes of stingless bee communities by using museum specimens and revisiting a previous effort that sampled stingless bee communities across varying levels of deforestation at 183 sites in Rondônia, Brazil, in 1996-1997. Body size measurements (intertegular distance) from 72 species collected were included as dependent variables in response to forest area, forest edge, and connectivity of forest patches at several spatial scales. We find that stingless bee body size is negatively related to forest cover: mean community body size was larger in areas with greater amounts of deforestation, and smaller in areas with less deforestation. Second, stingless bee species richness was positively associated with forest edge regardless of body size. Lastly, we find that as forest patch isolation increased, the stingless bee community body size also increased. These findings support hypotheses that small stingless bee species might be more negatively affected by deforestation, adding to the growing body of evidence that stingless bees require areas of intact forest in near proximity to other forest patches to conserve these diverse pollinator communities.

Detection of sodium chloride in cured salmon roe by SW-NIR spectroscopy

Salt and moisture content of cured salmon roe (ikura) was determined using short-wavelength-near-infrared (SW-NIR) reflectance spectroscopy (600-1100 nm). SW-NIR can be used to measure chloride species. Calibrations for salt in bulk samples of high-quality roe (R(2) = 0.904, SEP = 0.421%, RPD = 3.21) and average-quality roe (R(2) = 0.711, SEP = 1.13%, RPD = 1.81), crushed eggs (R(2) = 0.857, SEP = 0.509%, RPD = 2.62), and individual eggs (R(2) = 0.731, SEP = 0.698%, RPD = 1.98) were developed using partial least squares (PLS) regression models. The heterogeneous distribution of lipid and moisture in the individual eggs limit the sensitivity of this method; however, this method provides a rapid nondestructive method for high-value food products where destructive testing is expensive or impractical and for process control applications.

Somatomedin C (insulin-like growth factor I) levels in patients with chronic fatigue syndrome

Chronic fatigue syndrome is a disorder clinically quite similar to fibromyalgia syndrome, and it is of interest to examine if these two syndromes have pathogenetic as well as clinical features in common. Somatomedin C levels have been found to be lower in patients with fibromyalgia syndrome than in healthy controls. An attractive hypothesis relating sleep disturbance, altered somatotropic neuroendocrine function and fibromyalgia symptoms has been put forward as a plausible pathogenic mechanism for fibromyalgia syndrome. We therefore sought to investigate the level of somatomedin C in patients with chronic fatigue syndrome. Somatomedin C levels were determined by radioimmunoassay in frozen serum specimens from 49 patients with CFS and 30 healthy blood donor control subjects of similar age and gender. Somatomedin C levels were higher in patients with CFS than in healthy control subjects (255.3 +/- 68.5 vs 211.9 +/- 76.2, P = 0.01). There was no effect of gender, use of nonsteroidal anti-inflammatory drugs or tricyclic drugs on levels of somatomedin C. There was a tendency for somatomedin C levels to fall with age. In contrast to patients with fibromyalgia, in whom levels of somatomedin C have been found to be reduced, levels in patients with CFS were found to be elevated. Thus, despite the clinical similarities between these two conditions, they may be associated with different abnormalities of sleep and/or of the somatotropic neuroendocrine axis.

Adrenal steroidogenesis in very low birth weight preterm infants

Adrenal steroidogenesis was evaluated in 25 sick premature infants with a gestational age of less than 30 weeks. ACTH stimulation tests were performed on the fourth day of life using synthetic ACTH (36 micrograms/kg). Considering the stress and degree of illness, preterm newborns had low basal cortisol levels (mean +/- SEM, 207.4 +/- 23.5 nmol/L), and their levels were similar to basal levels reported for healthy full-term newborns (170.7 +/- 26.8 nmol/L; P = 0.31; reference data from Endocrine Sciences, Inc., Calabasas Hills, CA). However, compared to term neonates, preterm infants had markedly elevated basal levels of 17-hydroxypregnenolone (54.3 +/- 11.2 nmol/L), 17-hydroxyprogesterone (19.7 +/- 4.0 nmol/L), and 11-deoxycortisol (19.1 +/- 3.3 nmol/L), which were 7-, 18-, and 8-fold higher, respectively, than values for term infants. The activity of 3 beta-hydroxysteroid dehydrogenase was not significantly reduced in extremely premature neonates (mean basal ratio of 17-hydroxypregnenolone/17-hydroxyprogesterone, 2.9 +/- 0.2; ACTH-stimulated ratio, 6.5 +/- 0.4). In contrast, the mean basal substrate/product ratio of 11-deoxycortisol was markedly elevated in the preterm infants (11.9 +/- 2.2, ratio x 10(-2) compared to that in the full-term infants (2.1 +/- 0.4, ratio x 10(-2); P < 0.001). These findings are consistent with decreased activity of 11 beta-hydroxylase (11 beta OH) in preterm infants born at less than 30 weeks gestation. Decreased 11 beta OH activity appears to be more prominent than the deficiency of 3 beta-hydroxysteroid dehydrogenase that has been found in infants with lesser degrees of prematurity, suggesting that 11 beta OH activity may be regulated during fetal development to increase during the latter part of gestation.

Noninvasive method for monitoring ethanol in fermentation processes using fiber-optic near-infrared spectroscopy

Short-wavelength near-infrared (SW-near-IR) spectroscopy (700-1100 nm) is used for the determination of ethanol during the time course of a fermentation. Measurements are performed noninvasively by means of a photodiode array spectrometer equipped with a fiber-optic probe placed on the outside of the glass-wall fermentation vessel. Pure ethanol/water and ethanol/yeast/water mixtures are studied to establish the spectral features that characterize ethanol and to show that determination of ethanol is independent of the yeast concentration. Analysis of the second-derivative data is accomplished with multilinear regression (MLR). The standard error of prediction (SEP) of ethanol in ethanol/water solutions is approximately 0.2% over a range of 0-15%; the SEP of ethanol in ethanol/yeast/water solutions is 0.27% (w/w). Results from the mixture experiments are then applied to actual yeast fermentations of glucose to ethanol. By use of a gas chromatographic method for validation, a good correlation is found between the intensity of backscattered light at 905 nm and the actual ethanol. Additional experiments show that a calibration model created for one fermentation can be used to predict ethanol production during the time course of others with a prediction error of 0.4%.

Adrenal steroidogenic function in a black and Hispanic population with precocious pubarche

Adrenal steroidogenic function was evaluated in 34 children with precocious pubarche (PP; onset of pubic hair, less than 8 yr in girls and less than 9 yr in boys). The adrenal steroid response to an iv bolus of ACTH-(1-24) in the patients (aged 9 months to 9 7/12 yr) was compared to that in 16 normal controls (prepubertal, n = 9; Tanner stage II pubic hair, n = 7). The patient population consisted of 20 Hispanics (17 from the Dominican Republic), 13 black Americans, and 1 black Haitian. All patients had normal stimulated levels of 17-hydroxyprogesterone (17-OHP), 11-deoxycortisol (compound S), and desoxycorticosterone, thereby ruling out 21-hydroxylase deficiency and 11 beta-hydroxylase deficiency, respectively. To evaluate for the presence of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) deficiency, the patients were classified on the basis of their 60-min delta 5-17-hydroxypregnenolone/17-OHP (delta 5-17P/17-OHP) ratio [PP1 (n = 13), less than or equal to 2 SD of Tanner I controls; PP2 (n = 17), greater than 2 SD above Tanner I controls and less than or equal to 2 SD Tanner II controls; and PP3 (n = 4), greater than 2 SD above Tanner II controls; 2.1 +/- 1.0, 6.1 +/- 1.7, and 16.1 +/- 3.3 for PP1, PP2, and PP3, respectively. delta 5-17P/17-OHP for PP1 vs. PP2, PP2 vs. PP3, and PP1 vs. PP3 were significantly different (P less than 0.05) by analysis of variance and multiple comparison testing using the Student-Newman-Keuls procedure. The four patients in PP3 were considered to have a possible nonclassical 3 beta-HSD deficiency. This diagnosis was supported by the fact that these patients had the greatest increment in delta 5-17P and dehydroepiandrosterone (DHEA) levels as well as the highest stimulated delta 5-17P/cortisol (delta 5-17P/F) ratio among the patient groups. In contrast to the ACTH-stimulated androgens there were no differences in the baseline delta 5-17P/170HP or androgens among the patient groups. Additionally, the 60-min delta 5-17P/17-OHP within the patient groups was highly correlated with the 60 min-values for delta 5-17P, DHEA, DHEA/delta 4-androstendione, and delta 5-17P/F. In the children with PP the mean bone age/chronological age (BA/CA) was 1.27 +/- .27, the mean BA/height age (BA/HA) was 1.09 +/- 0.25, and the mean HA/CA was 1.18 +/- 0.17. No differences were noted between the patient population groups in mean BA/CA, mean BA/HA, or mean HA/CA.(ABSTRACT TRUNCATED AT 400 WORDS)

Absence of nonclassical congenital adrenal hyperplasia in patients with precocious adrenarche

We studied 31 patients (28 girls and 3 boys), ranging in age from 3.2-7.9 yr, with precocious adrenarche defined by the presence of early sexual hair development, no signs of virilization, and bone age within +3 SD of the mean for chronological age. To determine if this symptom complex stemmed from any form of nonclassical (late-onset) congenital adrenal hyperplasia, an ACTH stimulation test was performed on each patient using a standard 0.25-mg dose of Cortrosyn, given as an iv bolus. Twelve pubertal children (7 girls and 5 boys) and 18 prepubertal children (11 girls and 7 boys) served as normal controls. Baseline and stimulated 17-hydroxypregnenolone (17-OHPreg), 17-hydroxyprogesterone, (17-OHP), 11-deoxycortisol, dehydroepiandrosterone, androstenedione, testosterone, and cortisol levels were measured. Using published nomogram standards for serum 17-OHP response to ACTH, no child with precocious adrenarche was diagnosed as having nonclassical 21-hydroxylase deficiency. Eight girls, however, had a stimulated 17-OHP value that exceeded the mean response for pubertal and prepubertal controls by more than +2 SD [range, 295-670 ng/dL (8.94-20.3 nmol/L)]. Stimulated 11-deoxycortisol values [less than 400 ng/dL (11.6 nmol/L)] ruled out any cases of nonclassical 11 beta-hydroxylase deficiency. No patient had nonclassical 3 beta-hydroxysteroid dehydrogenase deficiency, as defined by both the stimulated 17-OHPreg and the 17-OHPreg/17-OHP ratio to be more than +2 SD above the mean for pubertal children [1354 ng/dL (41.0 nmol/L) and 10.4, respectively]. In conclusion, we could not provide any biochemical evidence for nonclassical congenital adrenal hyperplasia in a large group of children with precocious adrenarche.

Differential effects of retinoids on DNA synthesis in calcium-regulated murine epidermal keratinocyte cultures

To study the possibility that the state of proliferation of epidermal keratinocytes can influence the action of retinoids, the rate of proliferation of murine epidermal keratinocytes was manipulated by growing the cells in media containing high or low concentrations of Ca++. In contrast to what other investigators have reported, keratinocytes cultured in medium containing 1.4 mM Ca++ proliferate faster, instead of slower, than cells cultured in medium with 0.09 mM Ca++. Other experiments showed that Ca++ was stimulatory to keratinocytes in medium containing a low level of growth factors, and inhibitory in medium containing a high level of growth factors, suggesting that the discrepancy could be due to a difference in the sera used. The high Ca++ cells prominently expressed the 48kD/56kD pair of keratin, showing that they were in a hyperproliferative state. Exposure of the faster growing high Ca++ cells to all-trans retinoic acid, 13-cis retinoic acid, etretinate, etretin, and arotinoid ethyl ester caused dose-dependent inhibition of DNA synthesis. In contrast, exposure of the slower growing low Ca++ cells to these retinoids resulted in dose-dependent stimulation of DNA synthesis. In addition, all-trans retinoic acid caused dose-related increases in cell number in the low Ca++ cultures. These findings correlate with the reported differential effects of retinoids on normal and hyperproliferative epidermis, and suggest that Ca++ and low growth factor-regulated keratinocyte cultures are useful for studying the mechanism of hyperproliferation and retinoid actions.

The role of corticosteroids in the regulation of myocardial Na, K-ATPase in normotensive and spontaneously hypertensive rats

Sodium, potassium-dependent adenosine triphosphatase (ATPase) of the renal tubule is known to be dependent on both gluco- and mineralocorticoids. Recent evidence suggests that corticosteroids may modulate ATPase activity at extrarenal sites. The myocardium contains glucocorticoid receptors to which mineralocorticoids can also bind. Thus, the possibility that myocardial ATPase is corticosteroid dependent was examined in the Wistar-Kyoto (WKY) normotensive rat and also in the spontaneously hypertensive (SH) rat, a strain previously shown to exhibit reduced myocardial ATPase activity. WKY and SH rats (in groups of 10) were either sham operated or adrenalectomized and placed on 1% NaCl solution as drinking water. Adrenalectomized rats subsequently received daily intraperitoneal injections of either vehicle (1% NaCl, 0.5 ml), aldosterone (30 micrograms/kg) or dexamethasone (60 micrograms/kg). Renal cortical and myocardial ATPase activities were determined 21 days later in all groups. Adrenalectomized WKY rats had reduced myocardial ATPase activity (5.15 +/- 0.88 vs 8.18 +/- 0.93 mumol of phosphate h-1 mg-1 of protein in controls; P less than 0.01). This observed decrease in ATPase in adrenalectomized rats could be at least partly prevented by selective aldosterone or dexamethasone replacement. Parallel changes were observed with renal cortical ATPase. SH rat myocardial ATPase was lower than in WKY rats (P less than 0.05, 5.88 +/- 0.99 mumol of phosphate h-1 mg-1 of protein) and was unaffected by adrenalectomy (5.47 +/- 0.68 mumol of phosphate h-1 mg-1 of protein) whether accompanied by aldosterone (6.08 +/- 0.68 mumol of phosphate h-1 mg-1 of protein) or dexamethasone (6.47 +/- 0.84 mumol of phosphate h-1 mg-1 of protein) therapy or not.(ABSTRACT TRUNCATED AT 250 WORDS)

Dopaminergic modulation of aldosterone secretion in the rhesus monkey: evidence that dopamine affects the late pathway of aldosterone biosynthesis by inhibiting the conversion of corticosterone to 18-hydroxycorticosterone

This study was designed to investigate the role of dopaminergic mechanisms in the control of aldosterone secretion. Six rhesus monkeys received metoclopramide (1.25 mg, iv), with 5% dextrose (vehicle) or with dopamine (4 micrograms/kg . min) infusions begun 60 min before the administration of the dopamine antagonists. Metoclopramide, in the presence of vehicle, increased plasma aldosterone concentrations from 4.5 +/- 0.5 ng/dl to a maximum of 26 +/- 4.1 ng/dl and PRL concentrations from 8.1 +/- 1.3 ng/ml to a maximum of 118.4 +/- 7.6 ng/ml. Dopamine infusion inhibited the aldosterone and PRL responses to metoclopramide. The administration of metoclopramide resulted in a rise in plasma 18-hydroxycorticosterone from 10.4 +/- 1.5 ng/dl to a maximum concentration of 41 +/- 4.2 ng/dl. The aldosterone and 18-hydroxycorticosterone responses displayed a parallel time course, with significant responses of both occurring 5 min after metoclopramide administration. Plasma concentrations of electrolytes, PRA, plasma cortisol, 11-deoxycorticosterone, corticosterone, and 18-hydroxy-11-deoxycorticosterone were not altered by metoclopramide. The results of this investigation demonstrate that aldosterone and PRL responses to metoclopramide are mediated by their antagonist activities at dopamine receptors. Rather than simply affecting secretion, dopaminergic mechanisms appear to modulate the late pathway of adrenal glomerulosa biosynthesis of aldosterone. A parallel time course of stimulation of 18-hydroxycorticosterone and aldosterone secretion, with no change in other aldosterone precursors, strongly suggests that dopamine modulates the activity of the glomerulosa 18-hydroxylase enzyme.

Dopaminergic modulation of 18-hydroxycorticosterone secretion in man

This study was designed to investigate mechanisms of dopaminergic control of corticosteroid secretion and to determine on which step in the aldosterone biosynthetic pathway dopamine exerts its effects. Plasma concentrations of electrolytes, PRA, plasma cortisol, 11-deoxycorticosterone, corticosterone (18-OHB), and 18-hydroxy-11-deoxycorticosterone were not altered by the iv administration of 10 mg metoclopramide in six healthy male volunteers. Metoclopramide increased plasma aldosterone from 6.3 +/- 0.9 ng/dl to a maximum of 23.0 +/- 3.4 ng/dl, plasma 18-OHB from 11.4 +/- 1.1 ng/dl to a maximum level of 42.8 +/- 4.4 ng/dl, and PRL from 9.9 +/- 1.4 ng/ml to a maximum of 71.0 +/- 5.5 ng/ml. The aldosterone and 18-OHB responses displayed a parallel time course, with significant responses of both occurring with 5 min after metoclopramide administration. Dopamine infusions (3 micrograms/kg . min) begun 60 min before the administration of metoclopramide markedly decreased the 18-OHB as well as the aldosterone and PRL responses to the dopamine antagonist. A parallel time course of stimulation of 18-OHB and aldosterone secretion with no change in other aldosterone precursors suggests that dopamine may modulate the activity of the glomerulosa 18-hydroxylase enzyme. Thus, rather than simply affecting aldosterone secretion, dopaminergic mechanisms appear to modulate the biosynthesis of aldosterone.

Urinary and serum steroid concentrations in the management of congenital adrenal hyperplasia. Lack of physiologic correlations

Serum concentrations of 17-hydroxyprogesterone, dehydroepiandrosterone, dehydroepiandrosterone sulfate, progesterone, testosterone, and androstenedione and 24-hour excretion of 17-ketosteroids and pregnanetriol were measured serially in 18 children with congenital adrenal hyperplasia (21-hydroxylase deficiency) during a two-year period. Correlations were sought between results of measurements of these steroids and clinical progress assessed by physical examination and skeletal maturity to determine if measurement of concentration of these substances at a single point in time could be used to gauge the dose of corticosteroids for optimum treatment. We found that these measurements of steroids were generally not useful indicators of optimum control of the disease. Repeated careful clinical examination and assessment of changes in growth velocity and skeletal maturation seem to be the best criteria on which to base dosage of corticosteroids used for therapy.

Serum Androgens and sex hormone binding globulin in obese Pima indian females

Levels of serum androgens and sex hormone binding globulin (SHBG) were measured in 20 obese Pima Indian females aged 19-44 and compared with those of normal-weight Caucasians aged 20-46. The Pima exhibited significantly decreased SHBG compared to Caucasians, but a strong effect of age on androgen levels rendered mean comparisons useless. Androstenedione (A) and dehydroepiandrosterone-sulfate (DHEA-S) decreased significantly, and testosterone (T) declined slightly with age in the Pima, whereas these androgens showed no significant decreases in Caucasians for this age range. A possible relationship of androgens to the Pima female's propensity for android obesity as well as possible effects of obesity on SHBG, and aging is discussed.

Plasma corticosteroid concentrations during spironolactone administration: evidence for adrenal biosynthetic blockade in man

Spironolactone, a mineralocorticoid antagonist, may also inhibit aldosterone biosynthesis. In vitro studies suggest that spironolactone and its major metabolites inhibit adrenal 18- and 11 beta-hydroxylase activity. We examined various adrenal corticosteroids and their precursors, plasma renin activity, aldosterone excretion rate, and serum and urine electrolytes in normal subjects before and on days 5 and 10 of spironolactone administration (400 mg/day). Plasma corticosteroids were also examined 60 min after ACTH (Cortrosyn) 0.25-mg iv bolus. RIAs were performed after extensive chromatography; there was no interference of spironolactone and its metabolites in the assays. All studies were performed in supine subjects in metabolic balance on a constant 120-meq sodium intake. Plasma renin activity was increased (P less than 0.001) on both days 5 and 10 of spironolactone. Plasma aldosterone (PA) and the aldosterone excretion rate increased (P less than 0.01) on day 5 of spironolactone but decreased (P less than 0.01) from day 5 to 10. Both 11-deoxycorticosterone and 18-hydroxycorticosterone were increased from day 5 to 10. Corticosterone, progesterone, and dehydroepiandrosterone did not increase significantly during spironolactone administration. Incremental PA response to ACTH was less than control on day 10 of spironolactone, but other corticosteroid responses to ACTH were not different during control and days 5 or 10 of treatment. Reduction in PA and further elevation in its precursors during the second 5-day period of spironolactone therapy suggests inhibition of aldosterone biosynthesis during this phase of treatment in normal man. The disproportionate increments in 18-hydroxycorticosterone and 11-deoxycorticosterone suggest biosynthetic inhibition at the 18-dehydrogenase and 11 beta-hydroxylase sites.

Mineralocorticoid response to low dose adrenocorticotropin infusion

The adrenocorticoid responses to low dose ACTH of plasma aldosterone (aldo), corticosterone (B), 11-deoxycorticosterone (DOC), 18-hydroxycorticosterone (18-OHB), 18-hydroxycorticosterone (18-OH-DOC), and cortisol (F) were compared. Alpha ACTH-)1-24) was infused beginning at 0800 h at increasing rates from 12.5-200 mIU/30 min in supine normal subjects under the following conditions: 1) regular Na (120 meq) diet, 2) low Na (10 meq) diet, 3) dexamethasone preadministration (0.5 mg every 6 h for 48 h), and 4) night study (2000 h; 120 meq Na intake). Plasma 18-OH-DOC and B demonstrated quantitatively the greatest responses to ACTH, while DOC and 18-OHB responses were intermediate. Increments in aldo and F were least after ACTH and were maximum at 50 mIU/30 min ACTH, whereas other corticosteroids demonstrated linear responses up to infusion rates of 200 mIU/30 min. All corticosteroids, however, were similar in their threshold responses to ACTH which were at infusion rates of approximately 7-9 mIU/30 min. Na restriction enhanced aldo and 18-OHB responses to ACTH 2- to 3-fold but did not alter the other corticosteroid responses. Dexamethasone pretreatment augmented aldo, 18-OHB, and F responses but did not change the responsitivity of the other corticosteroids to ACTH. Adrenal corticosteroid responses to ACTH were not significantly different between 0800 and 2000 h in subjects on 120-meq Na intake. Thus, corticosteroids show markedly different responses to physiological doses of ACTH, which may have more importance in their regulation than heretofore proposed. Dexamethasone pretreatment enhances aldo, 18-OHB, and F responses to ACTH but does not affect the responses of other corticosteroids. Contrary to reports in experimental animals, corticosteroid responses to ACTH in man do not differ from day to night.

Thyrotropin-releasing hormone increases plasma norepinephrine in man

Administration of exogenous thyrotropin-releasing hormone (TRH) in man leads to an increase in mean arterial blood pressure at 4 and 8 min after TRH. This increase in mean arterial blood pressure is preceded by an increase in plasma norepinephrine levels (maximum response of 274 +/- 42 pg/ml vs. basal 158 +/- 32, p less than 0.01). There was a nonsignificant tendency for epinephrine levels to rise. There was no alteration in plasma renin activity (basal 1.2 +/- 0.4 ng/ml/min vs. peak 1.4 +/- 0.3) or in plasma aldosterone (basal 5.0 +/- 0.6 ng/dl vs. peak 6.8 +/- 0.7). We conclude that TRH causes an increase in blood levels of catecholamines in normal man through undetermined mechanisms. The blood pressure changes associated with TRH administration may be related to norepinephrine release. Our findings also lend additional support that acute increases in prolactin have no effect on the renin-angiotensin-aldosterone system in man.

The measurement of 18-hyroxy-11-deoxycorticosterone in human plasma by radioimmunoassay

A radioimmunoassay method for the measurement of plasma levels of 18-hydroxy-11 -deoxycorticosterone (18 -OH-DOC) has been developed. The antiserum against 18-OH-DOC was produced in rabbits immunized against 18-OH-DOC-3-oxime-bovine serum albumin. Plasma (1-2 ml) was extracted with dichloromethane and chromatographed on paper. The purified extracts were incubated with antiserum at a 1/22,000 dilution for 1/2 hour at 37 degrees C and for 2 hours at 4 degrees C. Saturated ammonium sulfate was used to separate free from bound 18-OH-DOC. 1,2-3H-18-OH-DOC was added to all samples to correct for losses and to determine the percent free. Pyridine (0.1%) was added to solvents to maintain the stability of 18-OH-DOC. Recovery after extraction was 58 +- 8 (S.D)%. The accuracy and precision of the method were acceptable, and a sensitivity of 2 pg per sample enabled the measurement of very low levels of 18-OH-DOC. High specificity was demonstrated by a low blank value (0 +- 0.2 pg) and by demonstrating that alternative paper chromatography separation systems gave results not differing significantly from those obtained by the present method. The mean 8AM plasma 18-OH-DOC level was 8.5 +- 1.2 ng per 100 ml in18 normotensive control subjects. There was a marked response of plasma 18-OH-DOC to ACTH stimulation and dexamethasone suppression and a significant increase after 3 hours upright posture.