Formaldehyde and methylene glycol equivalence: critical assessment of chemical and toxicological aspects.

Due largely to the controversy concerning the potential human health effects from exposure to formaldehyde gas in conjunction with the misunderstanding of the well-established equilibrium relationship with its hydrated reaction product, methylene glycol, the concept of chemical equivalence between these two distinctly different chemicals has been adopted by regulatory authorities. Chemical equivalence implies not only that any concentration of methylene glycol under some condition of use would be nearly or completely converted into formaldehyde gas, but also that these two substances would be toxicologically equivalent as well. A relatively simple worst case experiment using 37% formalin (i.e., concentrated methylene glycol) dispels the concept of chemical equivalence and a review of relevant literature demonstrates that methylene glycol has no inherent toxicity apart from whatever concentration of formaldehyde that might be present in equilibrium with such solutions.

The human relevant potency threshold: reducing uncertainty by human calibration of cumulative risk assessments.

The 2008 National Research Council report "Phthalates and Cumulative Risk Assessment: Tasks Ahead," rejected the underlying premises of TEQ-like approaches - e.g., chemicals are true congeners; are metabolized and detoxified similarly; produce the same biological effects by the same mode of action; exhibit parallel dose response curves - instead asserting that cumulative risk assessment should apply dose addition (DA) to all chemicals that produce "common adverse outcomes" (CAOS). Published mixtures data and a human health risk assessment for phthalates and anti-androgens were evaluated to determine how firmly the DA-CAOS concept is supported and with what level of statistical certainty the results may be extrapolated to lower doses in humans. Underlying assumptions of the DA-CAOS concept were tested for accuracy and consistency against data for two human pharmaceuticals and its logical predictions were compared to human clinical and epidemiological experience. Those analyses revealed that DA-CAOS is scientifically untenable. Therefore, an alternative approach was developed - the Human-Relevant Potency-Threshold (HRPT) - that appears to fit the data better and avoids the contradictions inherent in the DA-CAOS concept. The proposed approach recommends application of independent action for phthalates and other chemicals with potential anti-androgenic properties at current human exposure levels.

Measurement of tissue oxidation-reduction state with carbon-13 nuclear magnetic resonance spectroscopy.

The oxidation state of tissues influences their response to cancer therapy. We have devised a novel approach to the measurement of thiol redox which is based on the relative nuclear magnetic resonance signal intensity from carbon-13 adjacent to sulfur in metabolites of the redox-sensitive phosphorothioate drug, S-2-(3-methylaminopropylamino)ethylphosphorothioic acid (WR3689). Incubation of WR3689 metabolites under oxidizing conditions results in quantifiable changes in the 13C nuclear magnetic resonance spectrum stoichiometrically related to the degree of oxidation in mouse liver homogenate in vitro. Drug oxidation is competitive with the oxidation of tissue-derived thiol groups under these conditions. Noninvasive measurement of redox state may assist in designing more effective strategies for altering normal and malignant tissue response to cancer therapy.

BRIGHTEN Heart: Design and baseline characteristics of a randomized controlled trial for minority older adults with depression and cardiometabolic syndrome.

OBJECTIVES: African American and Hispanic elderly are at elevated risk of both depression and cardiovascular disease, relative to non-Hispanic whites. Effective interventions are therefore needed to address depressive symptoms and to reduce these disparities. BRIGHTEN Heart was a behavioral randomized controlled trial to test the efficacy of a virtual team intervention in reducing depressive symptoms in minority elderly as measured by the 9-item Patient Health Questionnaire (PHQ9). STUDY DESIGN: 250 African American and Hispanic adults, age ≥60 years, with comorbid depression and overweight/obesity were randomized. Participants randomized to the Intervention condition received a social work evaluation, team-based electronic consultation, case management, and psychotherapy over a 12 month period. Control participants were enrolled in a membership program that provided health classes and other services to support chronic disease self-management. Blinded research assistants completed assessments at baseline, and 6 and 12 months postrandomization. RESULTS: The study population was characterized by low socioeconomic status, with 81.4% having a household income of less than $20,000. Although median depression scores were in the mild range, 25% of participants had scores showing moderate to severe depression at baseline. 75% of participants had four or more chronic conditions. Significant demographic and clinical differences were observed between the African American and Hispanic populations. CONCLUSIONS: BRIGHTEN Heart was designed to rigorously test the efficacy of a multi-level intervention to reduce comorbid depressive symptoms and cardiovascular risk in minority elderly. Investigators successfully recruited a cohort well suited to testing the study hypothesis.

Psychophysical responses to a speech stressor: correlation of plasma beta-endorphin levels at rest and after psychological stress with thermally measured pain threshold in patients with coronary artery disease.

OBJECTIVES: We tested the hypothesis that psychological stress alters plasma levels of opioid peptides and that these plasma levels are related to pain perception in patients with coronary artery disease. BACKGROUND: Public speaking psychological stress has previously been shown to be associated with silent ischemia. METHODS: After instrumentation and a 30-min rest period, venous blood samples for beta-endorphin were obtained before and immediately after psychological stress in 20 patients with coronary artery disease. Pain threshold was then assessed using a thermal probe technique at baseline and immediately after stress. Patients gave three brief speeches lasting a total of 15 min about real-life hassle situations. RESULTS: Psychological stress significantly increases plasma beta-endorphin levels (4.3 +/- 0.9 pmol/liter [mean +/- SE] at rest to 8.3 +/- 2 pmol/liter after stress, p < 0.05). There was a significant positive correlation between pain threshold and beta-endorphin levels after stress (r = 0.577, p = 0.008). This significant positive correlation was still present while rest blood pressure and change in blood pressure during stress were controlled for by analysis of covariance techniques. CONCLUSIONS: In patients with coronary artery disease and exercise-induced ischemia, public speaking produces psychological stress manifested by increased cardiovascular reactivity and causes an increase in plasma beta-endorphin levels that is significantly correlated with pain thresholds. These findings may explain the predominance of silent ischemia during psychological stress in patients with coronary artery disease.

Statistical analysis of repeated measures in psychiatric research.

We examined the statistical methods applied to research studies that used parallel-groups repeated measures designs. Sixty-three of the 343 articles that were published in four major psychiatry research journals during a 6-month period contained data of this type. Seven (11%) of the 63 articles applied a multivariate analysis of variance. Four (6%) used a univariate analysis of variance with an adjustment for correlated measures. Ten (16%) used a univariate analysis of variance without an adjustment for correlated measures. Twenty (32%) either reduced their repeated measurements to a single value, such as a maximum-change score in each group, or carried out multiple tests at several time points. Twenty-two (35%) of the reports did not provide enough information to allow readers to determine the type of analysis that was applied. We discuss the appropriate selection of analytical techniques for repeated measures designs.

Bupropion in depression. I. Biochemical effects and clinical response.

We studied the biochemical effects of bupropion hydrochloride, a unicyclic antidepressant, in 11 depressed patients. Plasma homovanillic acid level increased significantly in patients who had poor responses to treatment but not in patients who obtained good clinical responses. Although bupropion is characterized preclinically as a weak dopamine reuptake inhibitor without appreciable effects on norepinephrine (NE) reuptake, it reduced whole-body NE turnover without altering plasma NE levels at rest and following orthostatic challenge. There was a trend toward a reduction in cerebrospinal fluid 3-methoxy-4-hydroxyphenylglycol and homovanillic acid concentrations following bupropion treatment, although these changes did not achieve statistical significance. Reduction in whole-body NE turnover has now been described for six disparate antidepressant treatments. Poor clinical outcome following treatment with bupropion may be related to perturbations in dopaminergic systems.

Severe stress, depressive symptoms, and changes in lymphocyte subsets in human immunodeficiency virus-infected men. A 2-year follow-up study.

BACKGROUND: This study examined how severe stress and depressive symptoms were related to changes in immune measures during a 2-year period in a sample of gay men with human immunodeficiency virus (HIV) infection. These analyses follow up our initial cross-sectional observations that severe stress was correlated with lower levels of natural killer (NK) cells and CD8+ T lymphocytes in these men. METHODS: Data were collected in North Carolina as part of an ongoing, longitudinal study, the Coping in Health and Illness Project. Sixty-six HIV-infected gay men, who were asymptomatic at baseline, were assessed systematically at 6-month intervals. RESULTS: Severe stress and depressive symptoms were independently related to decreases on immune measures from entry to 2-year follow-up, that is, declines in CD8+ T cells and CD56+ and CD16+ NK cell subsets. Subjects most likely to have decreases on these immune measures were those who scored above the median on both stress and depressive symptoms. CONCLUSIONS: Our findings are among the first prospective data showing that stress and depressive symptoms, especially when they occur jointly, are associated with decreased number of NK and CD8+ T lymphocytes in HIV-infected men. Since these immune cells may play a protective role in the progression of HIV infection, our data suggest that stress and depressive symptoms may have clinical implications for the course of this disease.

The effects of dexamethasone on plasma homovanillic acid and 3-methoxy-4-hydroxyphenylglycol. Evidence for abnormal corticosteroid-catecholamine interactions in major depression.

We investigated the possible interactions between corticosteroids and catecholamines in depression by studying the effects of the synthetic glucocorticoid dexamethasone on plasma levels of homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) in a group of depressed patients and normal controls. In comparison with metabolite levels on a control day, normal controls showed a significant dexamethasone-induced increase in the plasma HVA level and a trend toward a decrease in the plasma MHPG level at 4 PM following dexamethasone administration (1 mg orally at 11 PM). Conversely, depressed patients, particularly those with psychotic features, showed a significant dexamethasone-induced increase in the plasma MHPG level and a blunting of the plasma HVA response relative to the normal controls. Dexamethasone-induced increases in the plasma MHPG level were directly correlated with the severity of depressive symptoms and with postdexamethasone cortisol levels in the depressed patients. These data suggest abnormal corticosteroid-catecholamine interactions in depression and, specifically, in depressed patients with psychotic features.

Bupropion in depression. II. The role of metabolites in clinical outcome.

We studied the steady-state pharmacokinetics of bupropion hydrochloride, a unicyclic aminoketone antidepressant, in depressed patients. The metabolites hydroxybupropion (HB), threohydrobupropion, and erythrohydrobupropion predominated over the parent compound in plasma and cerebrospinal fluid at steady state. Plasma concentrations of each metabolite correlated with cerebrospinal fluid concentrations. Higher plasma metabolite concentrations were associated with poor clinical outcome. This relationship was most striking with HB; plasma HB levels were greater than 1250 ng/mL in all five nonresponders and less than 1200 ng/mL in all seven responders. Plasma HB levels correlated with postreatment plasma homovanillic acid levels. High levels of bupropion metabolites may be associated with poor clinical outcome due to toxic effects involving dopaminergic systems. Alternatively, a curvilinear dose-response relationship may exist for bupropion metabolites. Future studies should explore the clinical utility of plasma metabolite measurements in enhancing the efficacy of treatment with bupropion.

Antidepressants reduce whole-body norepinephrine turnover while enhancing 6-hydroxymelatonin output.

The effects of antidepressant treatment on noradrenergic function were studied in 27 patients with a major affective disorder. Twenty-four-hour urinary excretion of 6-hydroxymelatonin and "whole-body norepinephrine (NE) turnover," ie, 24-hour urinary output of NE and its major metabolites 3-methoxy-4-hydroxyphenylglycol, vanillylmandelic acid, and normetanephrine, were measured before and after treatment with the tricyclic desipramine hydrochloride, the aminoketone bupropion hydrochloride, the nonselective monoamine oxidase (MAO) inhibitor tranylcypromine sulfate, and the specific MAO type A inhibitor clorgiline. 6-Hydroxymelatonin excretion increased following antidepressant treatment, while at the same time whole-body NE turnover was reduced. These findings support the hypothesis that antidepressant therapy increases noradrenergic "efficiency," in that functional output, as measured by 6-hydroxymelatonin, is maintained while total NE production is decreased.

Selective antidepressants and cerebrospinal fluid. Lack of specificity on norepinephrine and serotonin metabolites.

Cerebrospinal fluid concentrations of the norepinephrine metabolite, 3-methoxy-4-hydroxyphenylglycol (MHPG), the serotonin metabolite, 5-hydroxyindoleacetic acid (5-HIAA), and the dopamine metabolite, homovanillic acid, were measured in depressed patients before and after treatment with three putatively specific antidepressants. The expected specificity of action on these three neurotransmitter metabolites was not observed. Desipramine hydrochloride, a norepinephrine uptake inhibitor, reduced 5-HIAA as well as MHPG concentrations; zimeldine hydrochloride, a serotonin uptake inhibitor, reduced MHPG as well as 5-HIAA concentrations; and clorgyline, a selective monoamine oxidase type A inhibitor, which might be predicted to most affect 5-HIAA, dramatically reduced MHPG, moderately reduced homovanillic acid, and only modestly reduced 5-HIAA concentrations.

Circulating natural killer cell phenotypes in men and women with major depression. Relation to cytotoxic activity and severity of depression.

The effects of major depression on peripheral blood natural killer cell phenotypes and natural killer cell activity were studied by comparing depressed and normal control subjects. Depressed subjects exhibited (1) significant reductions in Leu-11 (CD16) natural killer effector cells and natural killer cell activity and (2) a dissociation of the normal positive correlation between the percentage of Leu-11 cells and natural killer cell activity. These findings suggest that alterations in the availability and the killing capacity of circulating Leu-11 natural killer cells appear to be responsible for depression-related reductions in natural killer cell activity. Moreover, men with major depression showed marked reductions in Leu-11 cells, natural killer cell activity, and Leu-7 (HNK-1) lymphocytes compared with normal control men. By contrast, depressed women did not differ significantly from normal control women on any of these three immune function measures. Severity of depression as assessed by Hamilton Rating Scale for Depression scores was not associated with natural killer cell activity or Leu-7 lymphocyte levels in either men or women with major depression. Hamilton Rating Scale for Depression severity ratings were, however, strongly inversely correlated with Leu-11 lymphocyte counts among men, but not women, with major depression. These data begin to elucidate the immunological mechanisms by which natural killer cell activity is altered in depression and suggest that some measures of immunity may be differentially affected in male and female subjects with the syndrome of major depression.

Nondilated obstructive nephropathy.

Three patients had renal failure due to obstructive nephropathy associated with processes that prevented dilatation of the collecting systems. Thus, various radiologic procedures, including renal sonography, angiography, and isotope renography, all failed to identify an obstructing process. Because of the high index of clinical suspicion, surgical exploration and nephrostomy were performed on each patient. This confirmed the presence of obstructive nephropathy and led to marked improvement of renal function in each case. When renal failure develops in a setting with a high probability of ureteral obstruction, this diagnosis should be vigorously pursued despite normal radiologic results.

Amyloidosis secondary to drug abuse and chronic skin suppuration.

Amyloidosis has not been included in the wide spectrum of medical complications associated with drug abuse. Chronic visceral infection is a recognized cause of amyloidosis, but chronic suppuration of the skin is not a well-appreciated cause of this condition. Furthermore, to our knowledge, chronic skin suppuration secondary to parenteral drug abuse has not been reported as a cause for systemic amyloidosis. We report a case in which subcutaneous injections of narcotic tablets led to chronic skin suppuration and systemic amyloidosis.

Subclavian vein stenosis as a complication of subclavian catheterization for hemodialysis.

Thirteen patients had placement of a subclavian vein catheter for temporary vascular access for hemodialysis. Peripheral venography was performed within two to six weeks of catheter placement. Forty-six percent (six of 13 patients) developed subclavian vein narrowing, which resolved in two patients. The duration of catheter placement had no impact on the incidence of this complication. Subclavian vein catheterization can frequently lead to subclavian vein stenosis, which often will resolve spontaneously. Consideration should be given to placement of subclavian lines on the contralateral side of a planned permanent vascular access.

Elevated substance P levels in HIV-infected men.

The neuropeptide, substance P, is a potent modulator of neuroimmunoregulation. Substance P and its receptor modulate HIV infection. HIV-seropositive men had significantly higher plasma substance P levels compared with uninfected controls, which were associated with decreased CD16 and CD56 natural killer (NK) cell populations. The changes in plasma substance P levels and decreases in NK subsets did not correlate with CD4 cell levels, but a diurnal pattern was suggested for substance P. The balance between substance P expression and functions of immune cells may be important in the immunopathogenesis of HIV infection.

The effects of intravenous clomipramine on neurohormones in normal subjects.

The neuroendocrine effects of iv administration of clomipramine (CMI), a serotonin reuptake inhibitor, were studied in normal subjects. Under double blind, placebo-controlled conditions, single 10- and 20-mg doses of CMI were administered. Ten milligrams of CMI led to significant increases in plasma PRL and cortisol concentrations; plasma ACTH increased slightly but not significantly. In contrast, plasma GH, melatonin, and norepinephrine concentrations did not increase. Plasma PRL, ACTH, and cortisol levels increased significantly after 20 mg CMI; again, there were no significant changes in plasma GH, melatonin, or norepinephrine concentrations. All subjects tolerated the 10-mg dose well, but the 20-mg dose caused nausea in three of six subjects. Desmethylclomipramine, a metabolite that inhibits reuptake of norepinephrine, was not detectable in plasma after either CMI dose. These results support the hypothesis that serotonin is involved in the regulation of PRL, cortisol, and ACTH in humans.

Altered prolactin response to clomipramine rechallenge in healthy subjects.

The effect of an initial challenge with the serotonin (5-HT) uptake inhibitor clomipramine (CMI) on subsequent rechallenge was studied in healthy men who served as volunteers. Carefully screened volunteers were assigned to one of three conditions: (1) CMI challenge followed 2 weeks later by CMI rechallenge; (2) placebo challenge followed 2 weeks later by CMI challenge; and (3) CMI challenge followed 4 weeks later by CMI rechallenge. We found significant blunting of the prolactin response to CMI rechallenge 2 weeks (Signed Rank = -12, p = 0.05), but not 4 weeks after an initial challenge. Placebo challenge did not effect CMI challenge 2 weeks later. These findings suggest that a single exposure to IV CMI may cause 5-HT receptor changes that are present 2, but not 4 weeks later. The ramifications of this finding with regard to the use of 5-HT challenge paradigms in a test-retest design are discussed.

The effects of serotonin3 receptor blockade on the psychobiological response to intravenous clomipramine in healthy human subjects.

BACKGROUND: The purpose of this study was to determine the role that serotonin (5-HT)3 receptors play in the prolactin and nausea responses to clomipramine challenge. METHODS: Twenty healthy subjects were randomly assigned to pretreatment with either the selective 5-HT3 receptor antagonist ondansetron, or placebo, prior to intravenous infusion with clomipramine. RESULTS: Ondansetron pretreatment had no effect on the prolactin response to clomipramine challenge. There was a trend toward decreased nausea with ondansetron pre-treatment. CONCLUSIONS: These findings are consistent with other data suggesting that 5-HT3 receptors do not play a major role in the prolactin response to 5-HT challenge in human subjects, but may mediate nausea associated with enhanced 5-HT neurotransmission.