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Biomedical subjects

J C Ritchie

Publications and source records attributed to J C Ritchie.

At least 55 records · Page 3Linked to original sources
PubMed1991

Alterations in the hypothalamic-pituitary-adrenal axis in a proposed animal model of depression with genetic muscarinic supersensitivity.

Rats from the Flinders Sensitive Line (FSL) and Flinders Resistant Line (FRL), which have been bred for differences in sensitivity to cholinergic agonists, were killed by decapitation under quiet, nonstressful conditions and the concentrations of corticotropin-releasing factor (CRF) in various brain regions, the concentrations of CRF receptors in the anterior pituitary, and plasma ACTH and corticosterone concentrations were determined. A first study revealed that the cholinergically hypersensitive FSL rats exhibited lower concentrations of CRF in the median eminence, locus ceruleus, and prefrontal cortex, but no such changes in some 13 other brain regions. In this first study, the FSL rats had significantly lower plasma ACTH concentrations. However, there were no differences in plasma corticosterone concentrations between the two groups. A second study confirmed the results of the first study and revealed that the density of anterior pituitary CRF receptor binding sites was elevated in the FSL rats. The observed pattern of alterations in these measures of HPA axis activity suggest that the cholinergically supersensitive FSL rats may possess diminished HPA activity.

Adrenocorticotropic Hormone↗
PubMed1990

Nocturnal and early morning secretion of ACTH and cortisol in humans.

It is well established that the adrenocorticotropic hormone (ACTH) stimulates the synthesis and release of cortisol from the adrenal cortex, but the role of ACTH in the physiological regulation of basal cortisol secretion has received surprisingly little study. The authors studied the nocturnal and early morning secretory pulses of cortisol and ACTH in normal subjects. A pulse detection algorithm was developed. The relationship between ACTH and cortisol pulses in terms of temporal and proportional relationship is described. Pulse concomitance for ACTH with cortisol was 47% and for cortisol with ACTH pulses it was 60%. The first description of the relationship between concomitant ACTH and cortisol pulse magnitudes in humans is presented. A highly significant linear relationship between the magnitudes of ACTH and cortisol pulses is shown. Putative reasons for dissociated pulses and the potential implication of these findings are discussed.

Adrenocorticotropic Hormone↗
PubMed1990

Plasma dexamethasone concentrations and the dexamethasone suppression test.

Altered bioavailability or altered pharmacokinetics of dexamethasone (dex) may contribute to a positive Dexamethasone Suppression Test (DST) in psychiatric patients. We measured plasma dex and plasma cortisol concentrations in 32 patients with primary major depressive disorder (MDD), 14 patients with other psychiatric disorders, and 16 normal controls. Cortisol was measured by the competitive protein binding (CPB) assay and dex by RIA (IgG Corp.). Additionally, cortisol was measured by a fluorescent polarization immunoassay (FPIA) available on the Abbott TDx analyzer in an attempt to validate this method for use in the DST. The agreement between FPIA and CPB cortisol results was excellent. Depressed nonsuppressors, by definition, had significantly higher mean plasma cortisol concentrations than depressed suppressors, psychiatric controls, and normal volunteers at 8:00 AM, 3:00 PM, and 10:00 PM postdex. When DST nonsuppressors and suppressors were compared regardless of diagnostic group, plasma dex concentrations were significantly lower (p less than 0.01) in the DST nonsuppressors. There was a significant negative correlation between plasma cortisol levels and plasma dex levels across all subjects at 8:00 AM (r = -0.365, n = 44, p less than 0.05). When the subjects were sorted by diagnostic category, there was a strong, but not statistically significant, trend toward lower plasma dex concentrations in the melancholic nonsuppressors versus the melancholic suppressors and between the psychiatric control non-suppressors and the corresponding suppressor group. These relationships disappeared when we restricted our analyses to an empirically derived middle range of plasma dex concentrations within which the DST results were considered to be valid. We conclude that bioavailability or pharmacokinetics of dex may significantly contribute to DST results. Further investigation is needed to determine whether or not the quantification of dex and its metabolites and their determination at which specific timepoints during the DST will enhance the predictive or interpretive value of the DST in psychiatric patients.

Adult↗
PubMed1990

Pharmacokinetics of growth hormone secretion in humans induced by growth hormone releasing hormone.

This investigation compares the age- and sex-related changes in growth hormone (GH) response to growth hormone releasing hormone (GHRH) in normal subjects using an appropriate pharmacokinetic model. Twenty-five subjects (14 males and 11 females) aged 23-89 yr received a single intravenous bolus dose (1 microgram/kg) of GHRH-40 solution. Plasma GH concentration-time profiles are best characterized by a biexponential equation (or one-compartment model) with first-order release and disappearance rates and an equilibration lag time. The harmonic mean release rate half-life is similar for both sexes (males: 12.6 min vs. females; 11.4 min) but significantly different across age groups (23-35 yr: 7.2 min vs. 50-89 yr: 16.8 min). The mean disappearance rate half-life and GHRH-equilibration time lag for females (33.6 and 20.4 min, respectively) and the higher age group subjects (32.4 and 21.6 min, respectively) are significantly longer than those of males (22.8 and 9 min, respectively) and the lower age-group subjects (21.6 and 8.4 min, respectively). The mean metabolic clearance rate of GH is significantly lower (p less than 0.02) for females than for males (3.1 vs. 4.83 ml/hr.m2). However, the production rate and the amount of GH released by the pituitary for our subjects appear to be very similar for both males (8.7 micrograms/hr.m2 and 4.65 micrograms/m2) and females (9.33 micrograms/hr.m2 and 5.11 micrograms/m2).

Adult↗
PubMed1990

Differential diagnosis and pathophysiology of Cushing's syndrome and primary affective disorder.

Most patients with major depression have increased 24-hour urinary free cortisol and cortisol nonsuppression after dexamethasone administration, which are cornerstones of a diagnosis of Cushing's syndrome. Similarly, Cushing's syndrome patients often suffer from major psychiatric syndromes, most often depression. These similarities between the two conditions sometimes make it difficult to differentiate them and have led some investigators to suggest they are two points on a spectrum of endocrinologic dysfunction. This article reviews the literature comparing Cushing's syndrome and primary affective disorder and presents two cases that illustrate just how closely these diseases may resemble one another.

Adrenocorticotropic Hormone↗
PubMed1990

Brain IL-1-induced immunosuppression occurs through activation of both pituitary-adrenal axis and sympathetic nervous system by corticotropin-releasing factor.

Intracerebroventricular infusion of femtomolar quantities of interleukin-1 (IL-1) or stimulated release of endogenous IL-1 in the brain suppresses various cellular immune responses, decreasing natural killer cell (NK) activity, response to mitogen, and interleukin-2 production of splenic and blood lymphocytes (an effect hereafter called "brain IL-1-induced immunosuppression"). The present study examines mechanisms by which IL-1 produces this effect. First, because IL-1 in the brain activates the pituitary-adrenal axis by stimulating release of corticotropin-releasing factor (CRF), the role of CRF was investigated. To block CRF, affinity-purified antibody to CRF was infused into the lateral ventricle 30 min before introduction of IL-1. When this was done, suppression of cellular immune responses that normally follow IL-1 infusion was completely prevented. Infusion with an equal quantity of non-CRF IgG prior to IL-1 was without effect. Second, the role of sympathetic nervous activity was examined. To block neural transmission at sympathetic ganglia, chlorisondamine (3.0 mg/kg) was injected intraperitoneally 60 min before IL-1 infusion. When this was done, suppression of immune responses by IL-1 was partially blocked. These results indicate that IL-1 in the brain suppresses various cellular immune responses by activating both the pituitary-adrenal axis and the sympathetic nervous system, and that these systems are both activated through the influence of IL-1 on CRF.

Animals↗
PubMed1989

The corticotropin-releasing hormone test in patients with posttraumatic stress disorder.

To evaluate the hypothalamic-pituitary-adrenal (HPA) axis in patients with posttraumatic stress disorder (PTSD), we measured adrenocorticotropin hormone (ACTH) and cortisol responses following administration of corticotropin-releasing hormone (CRH) in 8 combat veterans with chronic PTSD. The PTSD patients had a significantly lower ACTH response to CRH compared to a control group of normal volunteers. Blunted ACTH responses occurred in patients with PTSD alone, as well as those PTSD patients who also had major depression. The cortisol response, although reduced, was not significantly different from normal. The blunted ACTH response to CRH in PTSD patients is similar to that seen in other psychiatric disorders, such as depression, panic disorder, and anorexia nervosa.

Adrenocorticotropic Hormone↗
PubMed1989

Intracerebroventricular infusion of interleukin 1 rapidly decreases peripheral cellular immune responses.

Low doses (50-200 pg or 3.1-12.4 fmol) of interleukin 1 (IL-1) infused into the brain of rats produced rapid suppression of various cellular immune responses in peripheral lymphocytes of rats. Fifteen minutes after infusion of purified IL-1 beta into the lateral ventricle, natural killer cell activity, response to phytohemagglutinin stimulation, and interleukin 2 production were markedly suppressed in lymphocytes isolated from blood and spleen. These effects were due to infusion of IL-1 into brain since they did not occur when IL-1 was infused into the cisterna magna (essentially posterior to brain) or was injected intraperitoneally. Effects of IL-1 in brain could be blocked by simultaneous infusion of alpha-melanocyte-stimulating hormone, which is known to block the biological actions of IL-1. To stimulate release of endogenous IL-1 in brain, lipopolysaccharide was infused; this produced similar effects as IL-1, and these effects also were blocked by alpha-melanocyte-stimulating hormone. At longer intervals after infusion of IL-1 and lipopolysaccharide (3, 6, and 24 hr), immune responses returned to baseline or remained suppressed; i.e., "rebound" immunopotentiation did not occur. Finally, IL-1 infusion suppressed cellular immune responses in adrenalectomized animals, thereby showing that the effects of central IL-1 on peripheral cellular immune responses were, at least in part, independent of the stimulatory effect of IL-1 on secretion of adrenal hormones. These results indicate a link from brain to peripheral immune responses by means of action of a cytokine acting in the brain.

Animals↗
PubMed1989

Growth hormone response to growth hormone releasing factor in Alzheimer's disease.

Because of the well-established reduction in the concentration of somatostatin in several brain areas of patients with histologically verified Alzheimer's disease, we sought to determine if growth hormone (GH) secretion is altered in Alzheimer's disease. In order to study this, we assessed the GH response to growth hormone releasing factor (GRF) in 8 patients with Alzheimer's disease and 8 age-matched controls. Although there was no difference between the magnitude of the GRF-induced GH response (delta max GH response or area under the curve) between the Alzheimer's disease patients and the controls, the Alzheimer's patients exhibited a delayed GH response to GRF.

Aged↗
PubMed1989

Plasma corticosterone in dexamethasone suppression test on depressed patients.

We retrospectively assayed plasma corticosterone (B) in 143 dexamethasone suppression tests (DST) given serially to 19 depressed patients during the course of their hospitalization. A total of 424 blood samples from these 19 patients were analyzed for both plasma cortisol (F) and B. Concentrations of plasma B were not distributed normally. To establish a cut-off point for a positive B value in the DST, we log transformed the values for B to approximate a normal distribution. Using this approach we determined that a value of 1.3 ng/ml is the most sensitive cut-off point for the plasma B-DST in our laboratory. The serial DST's were performed weekly during the patients' stay and plasma B values were compared with plasma F values. Severities were assessed by weekly Hamilton ratings (17 items). In general, the B values closely parallel the F values. The sensitivity of F-DST was 53% (20/38) and the sensitivity was 56% (20/36) for B-DST. During treatment, both B and F normalized in parallel and this correlated strongly with improvements in the patients' severity ratings. These data confirm the fact that plasma B is as good (but not better) a marker for depression as plasma F in the DST.

Adrenal Cortex Function Tests↗
PubMed1988

One stressful event blocks multiple actions of diazepam for up to at least a month.

Based on recent findings of this laboratory, the hypothesis was tested that a single stressful encounter might have a persistent antidiazepam influence. Our results indicate that one exposure to a brief stressful event up to at least one month earlier prevented completely the effect of diazepam on pentylenetetrazole-induced changes in dopamine in the rat frontal cortex, elevations of plasma corticosterone levels and seizures.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1988

Growth hormone response to growth hormone-releasing factor in depression.

A blunted growth hormone (GH) response to clonidine and other pharmacologic stimuli has been reported in patients with depression. This blunted growth hormone response to clonidine has led to the speculation that there is a central alpha-2 adrenergic receptor subsensitivity in depression. This hypothesis is based on the assumption that the pituitary somatotroph response to growth hormone-releasing factor (GHRF) is not altered in depression. In the present preliminary study, the somatotroph response to GHRF in depressed patients and normal controls has been evaluated in four depressed patients and four age- and sex-matched controls. The GH response to GRF is highly variable both in normal individuals and in the depressed patients studied. Larger numbers of patients and controls must be studied before any definitive conclusions can be drawn about GH responses to GRF in depressed patients.

Depressive Disorder↗
PubMed1988

Growth hormone-releasing factor stimulation test in depression.

The authors administered the growth hormone-releasing factor (GRF) stimulation test to 19 patients with major depression and 19 age- and sex-matched control subjects to test the hypothesis that a blunted growth hormone (GH) response to clonidine reflects a central alpha 2-adrenergic receptor subsensitivity in depression. GH response to GRF was significantly higher in patients with depression than in control subjects. This group difference was mainly attributable to three of the 19 depressed patients who exhibited markedly high GH responses to GRF. These results suggest that the blunted GH response to clonidine seen in patients with depression is not due to a pituitary defect in GH secretion.

Adult↗
PubMed1988

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.

Adrenocorticotropic Hormone↗
PubMed1986

Sulphoxidation of S-carboxymethyl-L-cysteine in the rhesus monkey (Macaca mulatta), cynomologus monkey (Macaca fascicularis), African green monkey (Cercopithecus aethiops) and the marmoset (Callithrix jacchus).

The metabolic pathways giving rise to the urinary metabolites of S-carboxymethyl-L-cysteine have been identified for the rhesus, cynomologus, African green and marmoset species of monkey. The formation of a sulphoxide metabolite from the sulphide precursor is a reaction important in these species. The metabolic profile displayed by the marmoset was distinct from the three Old World species, with the rhesus and cynomologus being similar to man.

Animals↗