Comparison of early and delayed inpatient dexamethasone suppression tests

Ninety-five inpatients completed a dexamethasone suppression test (DST) within 72 hours after admission and again after at least 1 week of medication-free hospital care. The frequency of cortisol nonsuppression in patients with endogenous depression (ED) was high and not significantly different at both tests. In patients with diagnoses other than ED, the higher rate of cortisol nonsuppression at the first DST was associated with a significant decrease in test specificity. Change in postdexamethasone cortisol levels at repeat testing was associated with a decrease in depressive symptomatology, but was not related to weight change during hospitalization.

Circadian rhythm of adrenergic regulation of adrenocorticotropin and cortisol secretion in man

The effects of the alpha-adrenergic agonist methoxamine on the human hypothalamic-pituitary-adrenal axis was assessed by a placebo-controlled study in the morning and one in the evening. A 5-mg iv bolus dose of methoxamine in normal subjects caused a significant rise in plasma ACTH and cortisol concentrations in the morning study. However, no significant change in plasma cortisol or ACTH concentrations was noted during the evening study. These studies suggest the existence of a diurnal variation in alpha 1-adrenergic regulation of the hypothalamic-pituitary-adrenal axis.

Inheritance of supernodulation in soybean and estimation of the genetically effective cell number

Provided the nature of inheritance is known, the frequency of homozygous mutant plants in individual M2 families (derived from M1 seed) can be used to estimate the genetically effective cell number (GECN). Segregation ratios in M3 families derived from M2 wild-type plants indicated that the supernodulation characters nts382, nts1007 and nts183 are inherited as Mendelian recessives. The nature of inheritance was also known or confirmed to be recessive by crossing the wild type to these and several other mutants derived from the same population of M2 families. Subsequently, using the frequency of mutant plants in individual M2 families, the GECN for soybean was calculated to be approximately two.

Solubilization kinetics of a triglyceride/n-alkane mixture in a non-ionic surfactant solution

The kinetics of solubilization in a non-ionic surfactant solution of pure n-hexadecane, pure triolein and a mixture of the two oils have been investigated. The rates were determined from observations of the dissolution of a single, microscopic droplet, using a drop-on-fibre technique. Conditions were such that negligible saturation of the micellar surfactant with solubilizate occurred. The rate of solubilization of each of the pure oils was found to be independent of time, hexadecane solubilization on a volume basis being about 8 times as rapid as that for triolein. The rate of solubilization of a mixture of the two oils, having a volume fraction 0.69 for triolein, was found to vary in the medium term, the rates apparently being steady both initially and (at a lower value) in the long term. These observations can be related quantitatively to the rates found for the pure oils.

Investigations of the solubilization kinetics of binary mixtures of non-polar oils by non-ionic surfactants

An investigation of the solubilization kinetics of binary mixtures of non-polar oils by a non-ionic surfactant has been made using the drop-on-fibre technique. Variables studied were the oil composition, surfactant concentration and the temperature. Rates vary linearly with the surfactant concentration for all oil compositions. The observed rate during nearly total solubilization of each oil drop was constant, implying that in these systems solubilization is non-selective. The rates increase as the lower consolute (cloud) temperature of the surfactant is approached. Activation energies of the solubilization process are shown to be independent of the oil composition for the system studied. This suggests that the important stage of the process involves dissociation of the surfactant micelles.

Lymphocyte numbers in endogenous depression

The blood counts of 80 patients with depression were examined (50 unipolar, 30 bipolar). Many had reduced numbers of circulating lymphocytes. This abnormality was more common in the unipolar group (52%) than in the bipolar group (27%). When those patients with an abnormal dexamethasone suppression test response in both groups were compared, the relative and absolute lymphocyte counts were significantly lower in unipolars. Although cortisol hypersecretion may reduce lymphocyte numbers it is not yet clear whether the findings can be satisfactorily explained in this way.

Regulation of the soybean-Rhizobium nodule symbiosis by shoot and root factors

The availability of soybean mutants with altered symbiotic properties allowed an investigation of the shoot or root control of the relevant phenotype. By means of grafts between these mutants and wild-type plants (cultivar Bragg and Williams), we demonstrated that supernodulation as well as hypernodulation (nitrate tolerance in nodulation and lack of autoregulation) is shoot controlled in two mutants (nts382 and nts1116) belonging most likely to two separate complementation groups. The supernodulation phenotype was expressed on roots of the parent cultivar Bragg as well as the roots of cultivar Williams. Likewise it was shown that non-nodulation (resistance to Bradyrhizobium) is root controlled in mutant nod49. The shoot control of nodule initiation is epistatically suppressed by the non-nodulation, root-expressed mutation. These findings suggest that different plant organs can influence the expression of the nodulation phenotype.

Isolation and Initial Characterization of Constitutive Nitrate Reductase-Deficient Mutants NR328 and NR345 of Soybean (Glycine max)

Two nitrate reductase deficient mutants of soybean (Glycine max [L.] Merr. cv Bragg) were isolated from approximately 10,000 M(2) seedlings, using a direct enzymic assay in microtiter plates. Stable inheritance of NR345 and NR328 phenotypes has been demonstrated through to the M(5) generation. Both mutants were affected in constitutive nitrate reductase activity. Assayable activities of cNR in nitrate-free grown seedlings was about 3 to 4% of the control for NR345 and 14 to 16% of the control for NR328. Both mutants expressed inducible NR during early plant development and were sensitive to nitrate and urea inhibition of nodulation. These new mutants will allow an extension of the characterization of nitrate reductases and their function in soybean. Preliminary evidence indicates that NR345 is similar to the previously isolated mutant nr(1), while NR328 is different.

Informed use of the dexamethasone suppression test

Like all laboratory tests, the dexamethasone suppression test (DST) should be used as an aid to diagnosis in specified clinical contexts. The test is not appropriate for routine screening for all psychiatric patients; it is most useful in those with a clinical picture of endogenous or melancholic depression for whom treatment with antidepressant drugs or ECT is being considered. In such cases, normalization of the DST may precede and be prognostic of clinical improvement. By contrast, failure of the DST to normalize in hospitalized patients being considered for discharge may be an indicator of possible relapse. Factors that can invalidate the DST, producing spurious false-positive results, are described, and the general principles for sound clinical use of the DST as a laboratory test in psychiatry are summarized.

Prolactin response to TRH in depression

We studied the prolactin response to TRH in 53 unmedicated psychiatric inpatients. The prolactin response of females was significantly greater than the response of male subjects. There was no significant difference in the prolactin response to TRH between depressed patients and those with other psychiatric diagnoses. There was no significant relationship between the prolactin response to TRH and the severity of depression, the TSH response to TRH or the resistance to suppression of cortisol secretion by dexamethasone.

Age effects in serial hypothalamic-pituitary-adrenal monitoring

To evaluate age effects on hypothalamic-pituitary-adrenal (HPA) regulation in depressives, we studied 65 patients with major depressive disorder, endogenous subtype. With each patient serving as his or her own control, we compared weekly dexamethasone suppression test (DST) results among three age subgroups (less than 40 years, n = 18; 40-70 years, n = 40; greater than 70 years, n = 7). The oldest patient group had higher mean post-dexamethasone plasma cortisol concentrations both before and after treatment, and more were DST nonsuppressors. Life table analyses revealed that elderly patients who were DST nonsuppressors had significantly slower patterns of normalization during treatment and that fewer elderly patients ever achieved normal suppression. The results indicate that age effects on HPA function may be confounded with other aspects of depression, such as severity, chronicity and number of previous episodes.

Depression, urinary free cortisol excretion and lymphocyte function

An impairment in lymphocyte response to mitogen stimulation, a correlate of cell-mediated immunity, has been reported in patients with depressive illness. To investigate whether such impairment in lymphocyte function is related to excessive secretion of cortisol, an immunosuppressive hormone, we compared mitogen-induced lymphocyte proliferation in three groups of subjects: depressed patients with elevated 24-hour urinary free cortisol (UFC) excretion; depressed patients with normal UFC excretion; and normal controls. Depressed patients in both groups showed significant reductions in lymphocyte mitogenic activity, in comparison with the normal controls, but the two depressive groups did not significantly differ from each other in their lymphocytic responses to any of the mitogens used. Furthermore, no significant correlations were found, within depressed patients, between UFC excretion and lymphocyte mitogenic responses. Depression is therefore associated with an impairment in lymphocyte function that cannot be explained solely on the basis of increased cortisol secretion.

Cortisol escape from morphine suppression

Twenty-one unmedicated, sequentially admitted psychiatric patients of either sex and four male healthy volunteers were given an intravenous injection of 2.5 mg morphine. Blood samples were drawn immediately before and at 30-minute intervals for 3 hours after the injection and assayed for cortisol. Morphine suppressed cortisol secretion. Early resumption of cortisol secretion (escape) was more frequent in patients with a diagnosis of major depressive disorder and with abnormal dexamethasone suppression test results. The sensitivity of this infusion paradigm for the diagnosis of major depressive disorder was 40%, and the specificity was 82%. The implications of these findings for the pathophysiology of depression are discussed.

Plasma cortisol determination for the dexamethasone suppression test. Comparison of competitive protein-binding and commercial radioimmunoassay methods

Quality control serum samples and postdexamethasone plasma pools were used to compare 16 commercial cortisol radioimmunoassay kits with the competitive protein-binding assay for plasma glucocorticoids that we used to standardize the dexamethasone suppression test (DST). Thirteen radioimmunoassays gave higher criterion values for the DST than those established using the competitive protein-binding assay. The range of radioimmunoassay criterion values was 4.34 to 8.70 mu mg/dL. Possible explanations are given for these findings, and their importance to the clinical utility of the DST are emphasized. Each laboratory should validate its own criterion cortisol value for depression based on local data, including appropriate control groups.

A Supernodulation and Nitrate-Tolerant Symbiotic (nts) Soybean Mutant

The nodulation characteristics of soybean (Glycine max) mutant nts382 are described. The mutant nodulated significantly more than the parent cultivar Bragg in the presence and absence of several combined nitrogen sources (KNO(3), urea, NH(4)Cl, and NH(4)NO(3)). The number of nodules on the tap root and on lateral roots was increased in the mutant line. In the presence of KNO(3) and urea, nitrogenase activity was considerably higher in nts382 than in Bragg. Mutant plants were generally smaller than wild-type plants. Although nts382 is a supernodulator, inoculation with Rhizobium japonicum was necessary to induce nodule formation and both trial strains CB1809 (= USDA136) and USDA110 elicited the mutant phenotype. Segregation of M(3) progeny derived from a M(2) wild-type plant indicated that the mutant character is inherited as a Mendelian recessive. The mutant is discussed in the context of regulation of nodulation and of hypotheses that have been proposed to explain nitrate inhibition of nodulation.

Opioid regulation of hypothalamic-pituitary-adrenal function in depression

A morphine infusion paradigm was used to investigate opioid mechanisms in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis in depression. The subjects were unmedicated psychiatric inpatients and healthy volunteers. Morphine suppressed cortisol secretion. Early resumption of cortisol secretion was associated with a diagnosis of major depression and abnormal dexamethasone suppression test results. Our data suggest that the hyperactivity of the HPA axis observed in depression is abnormally resistant to opioid inhibition as well as glucocorticoid feedback.

Prolactin response to morphine in depression

Twenty-two unmedicated inpatients with major depression and 18 healthy volunteers of either sex were given an intravenous injection of 5 mg morphine. Blood samples were drawn immediately before and at intervals for 3 hrs after the injection and assayed for prolactin. Morphine stimulated prolactin secretion. The prolactin response of females was significantly greater than the response of male subjects. There were no significant differences in the prolactin response to morphine between depressed and healthy subjects. The implications of these findings for the hypothesized role of the opioid system in the pathophysiology of depression are discussed.

Dexamethasone suppression test: a review of contemporary confusion

Reasons for the current controversy and confusion about the dexamethasone suppression test (DST) are reviewed, and basic axioms regarding use and interpretation of the test are reiterated. Problems with reliability and validity of current diagnostic systems limit their use as "gold standards" for evaluating the DST; accurate evaluation must await follow-up and treatment response studies. Interpretation of DST results in specific patients requires common sense, consideration of the clinical context, and attention to technical factors. While its ultimate significance is not yet known, the DST, like other laboratory tests, may help to resolve uncertainty in clinical diagnosis. Perhaps most important, it may help to refine current paradigms for psychiatric nosology and diagnosis.

Self-reported diurnal mood changes, early morning awakening and the dexamethasone suppression test in endogenous depression

Several authors have suggested that Dexamethasone Suppression Test (DST) non-suppression is related to circadian alternations of hypothalamic-pituitary-adrenal function. Two clinical manifestations of altered circadian rhythms in depressed patients are early morning awakening and diurnal variation in mood. To observe whether these clinical symptom patterns were associated with an increased frequency of abnormal DSTs, we examined post-DST plasma cortisol concentrations and matched clinical ratings of early morning awakening and diurnal variation in mood in 49 patients with major depressive disorder, endogenous subtype. We found no significant association between these clinical and laboratory variables.

Hypothalamic-pituitary-adrenocortical activity in patients with diabetes mellitus

Several clinical and physiologic associations between depression and diabetes mellitus have been reported. In this study, a potential neuroendocrine association was studied by measuring hypothalamic-pituitary-adrenocortical (HPA) axis activity in patients with diabetes mellitus. Plasma cortisol levels and response to dexamethasone administration were determined in 54 diabetics. Twenty-three (55%) of forty-two 1-mg dexamethasone suppression tests (DSTs) performed in 34 subjects, with eight repeated tests, and two (10%) of twenty 2-mg DSTs demonstrated a blunting of normal suppression. None of a variety of potential demographic, physiologic, or mood factors predicted nonsuppression. This study replicates prior findings that HPA dysfunction occurs in association with diabetes, and invalidates the use of the 1-mg DST as a diagnostic marker for melancholia in patients with diabetes.

Biological 'markers' for endogenous depression. Effect of age, severity of illness, weight loss, and polarity

The dexamethasone suppression test (DST) can differentiate between endogenous and nonendogenous depression. Similarly, EEG sleep patterns can differentiate primary from secondary depression, and this technique has also been used to make the endogenous-nonendogenous discrimination. However, a number of physiological variables associated with this diagnostic distinction may also affect the DST results and sleep architecture. With the use of multivariate statistical procedures, we found that although age and weight loss affect the results of both tests, both the DST and sleep EEG differentiate endogenous from nonendogenous depression when these variables are taken into account. Severity of illness affected both proposed diagnostic markers, but did not account for the differences between diagnostic groups, alone or when added to the physiological variables. The DST was more sensitive in unipolar than in bipolar endogenous depression, but there were no significant differences in the sleep of unipolar and bipolar patients.

Problems with diagnostic criteria for depression

Limitations of the three major psychiatric diagnostic systems are discussed, with particular reference to depression and its subtypes. The lack of demonstrated reliability and validity for standard diagnoses, and the use of these diagnoses as independent variables in clinical research, is criticized. Possible approaches to improving current classification methods include increased specificity and sensitivity of symptoms, differential weighting, and objective recording. Scientific validation procedures should be applied to the classification of depressions, including studies of natural history and course, specific antidepressant drug responses, and the use of laboratory markers such as the dexamethasone suppression test and sleep EEG parameters.