Biomedical subjects
Publications and source records attributed to A H Clayton.
Fibromyalgia is an enigmatic medical condition whose specific etiology remains undiscovered but currently plagues five million Americans. Research indicates that the origin of the disease is most likely multifactorial. Treatment should therefore be tailored accordingly. Thus, it is often necessary to combine different options in order to achieve the maximum benefit in patients suffering from fibromyalgia.
Premenstrual symptoms can pose significant problems for a large number of women; this small exploratory study was designed to investigate biological markers that may provide etiological clues. Using an algorithm based on daily symptom charting for two months, 15 participants were assigned to one of three study groups: non-symptomatic (n = 9), probable PMS (n = 3) and probable PMDD (n = 3). During two overnight admissions, one prior to and one following the onset of menses, participants had blood drawn to assess the level of available serotonin via one of its metabolites, 5-HIAA. The three groups exhibited potentially significant differences in several biological markers. This study's results are consistent with a hypothesis implicating serotonin in the generation of premenstrual symptomology.
OBJECTIVE: Gender differences in clinical presentation and response to sertraline treatment were examined for patients diagnosed with DSM-III-R panic disorder with or without agoraphobia. METHOD: Data was pooled from 4 double-blind, placebo-controlled outpatient studies (males, N = 335; females, N = 338). Two were 12-week fixed-dose studies (sertraline 50 mg vs. 100 mg vs. 200 mg) and 2 were 10-week flexible-dose studies (sertraline 50-200 mg). Primary outcome measures consisted of the Clinical Global Impression-Improvement scale (CGI-I) and change in panic attack frequency. RESULTS: The clinical presentation of panic disorder was similar except that men reported an earlier age of onset, shorter duration of illness, and significantly more frequent history of alcohol and/or substance dependence/abuse. Sertraline was significantly more effective than placebo in both women and men on the 2 primary outcome measures. When between-sex efficacy was compared, women achieved significantly greater improvement than men on panic frequency and CGI-I, but had equivalent improvement on all other measures. There was no significant between-sex difference in study completion rates, or in adverse event profiles. CONCLUSIONS: There was a modest but consistent trend for women to show superior efficacy at the end of acute sertraline treatment. This gender effect only occasionally achieved significance, and must be confirmed by future treatment research.
To aid the development of custom peptide antibiotics, a kinetic study of membrane lysis by cecropin B (CB) and its analogs, cecropin B1 (CB1) and cecropin B3 (CB3) was carried out to determine the mechanism by which these peptides disrupt the bilayer structure of liposomes of defined composition. Disruption of the phospholipid bilayer was determined by a fluorescence assay involving the use of dithionite to quench the fluorescence of lipids labeled with N-7-nitro-2,1,3-benzoxadiazol-4-yl. Lytic peptides caused the disruption of liposomes to occur in two kinetic steps. For liposomes composed of mixtures of phosphatidylcholine and phosphatidic acid, the time constants for each kinetic step were shorter for CB and CB1 than for CB3. Oriented circular dichroism experiments showed that the peptides could exist in at least two different membrane-associated states that differed primarily in the orientation of the helical segments with respect to the bilayer surface. The results are discussed in terms of kinetic mechanisms of membrane lysis. The mode of actions of these peptides used for the interpretation of their kinetic mechanisms were supported by surface plasmon resonance experiments including or excluding the pore-forming activities.
BACKGROUND: We examine changes in sexual functioning and depressive symptoms in patients' transition from a selective serotonin reuptake inhibitor (SSRI), which induced both a therapeutic response and sexual dysfunction, to bupropion sustained release (SR) over the course of an 8-week trial. METHOD: The study included 11 adults (8 women and 3 men) who had a DSM-IV diagnosis of major depressive disorder in remission (Hamilton Rating Scale for Depression [HAM-D] score < 11) and were receiving an SSRI. Depression (using the HAM-D) and sexual dysfunction (using the Changes in Sexual Functioning Questionnaire) were assessed at baseline, 2 weeks after bupropion SR was added to the current antidepressant (combined treatment), 2 weeks after taper of the SSRI was initiated and completed, and after 4 weeks of bupropion SR monotherapy. T tests were performed to assess changes in depression and sexual function. RESULTS: Patient participation dropped from the initial group of 11 at week 2 to 9 at week 4 and to 6 by week 8. Sexual functioning improved from week 0 (baseline) to week 2 and from week 2 to week 4. The patients showed no significant change in mean HAM-D scores in weekly comparisons during the study period; 55% of patients completed the substitution without significant adverse events or recurrence of depressive symptoms. CONCLUSION: Bupropion SR as a treatment for depression also alleviates sexual dysfunction due to SSRI treatment. Results show that sexual functioning improves after the addition of bupropion SR to SSRI treatment and continues to improve, after discontinuation of the SSRI, with bupropion SR treatment alone.
Recognition of sexual dysfunction associated with depression or its treatment is critical for patient satisfaction and medication compliance. This report reviews relevant literature related to types of sexual problems, the etiology of sexual dysfunction, prevalence rates, barriers to assessment, and available instruments for evaluating sexual functioning in individuals with depression. Evaluation of sexual functioning should include examination of each phase of the sexual response cycle, with classification of sexual disorders as described in the DSM-IV. Sexual functioning requires both an adequate hormonal milieu and appropriate neurotransmitter functioning. Evaluation of sexual functioning should include a sexual history, current level of sexual functioning, history and current diagnoses of medical and psychiatric illnesses, evaluation of medications and/or other substances taken, indicated endocrine measures, and targeted physical examination. Appropriate evaluation of sexual functioning associated with depression could help reduce the enormous societal costs of this disorder.
The effect of lipid phase state on the orientation and conformation of a class A alpha-helical peptide on aligned lipid multilayers was examined using oriented circular dichroism spectroscopy. A comparison of oriented spectra in aligned peptide-lipid multilayers with CD spectra of unaligned peptide lipid vesicle complexes is consistent with a preferential alignment of helices parallel to the membrane surface at temperatures above and below the main acyl-chain melting transition temperature of the phospholipid. Changes are observed in the oriented CD spectra with lipid phase state which are attributed to a subtle conformational change of the peptide on the lipid surface. The results are compared with available experimental data on membrane-active lytic and antimicrobial helical peptides.
The amphipathic helix plays a key role in many membrane-associating peptides and proteins. The dynamics of helices on membrane surfaces might be of importance to their function. The fluorescence anisotropy decay of tryptophan is a sensitive indicator of local, segmental, and global dynamics within a peptide or protein. We describe the use of frequency domain dynamic depolarization measurements to determine the site-specific tryptophan dynamics of single tryptophan amphipathic peptides bound to a phospholipid surface. The five 18-residue peptides studied are based on a class A amphipathic peptide that is known to associate at the interface of phospholipid bilayers. The peptides contain a single tryptophan located at positions 2, 3, 7, 12, or 14 in the sequence. Association of the peptides with egg phosphatidylcholine vesicles results in complex behavior of both the tryptophan intensity decay and the anisotropy decay. The anisotropy decays were biphasic and were fitted to an associated model where each lifetime component in the intensity decay is associated with a particular rotational correlation time from the anisotropy decay. In contrast, an unassociated model where all components of the intensity decay share common rotational modes was unable to provide an adequate fit to the data. Two correlation times were resolved from the associated analysis: one whose contribution to the anisotropy decay was dependent on the exposure of the tryptophan to the aqueous phase, and the other whose contribution reflected the position of the tryptophan in the sequence. The results are compared with existing x-ray structural data and molecular dynamics simulations of membrane-incorporated peptides.
The interaction of a peptide derived from the sequence of apolipoprotein C-II (apoC-II) with a model lipid surface has been investigated by fluorescence spectroscopy. ApoC-II19-39, labeled at the N-terminus with 7-nitrobenz-2-oxa-1,3-diazole (NBD), bound to small unilamellar vesicles of phosphatidylcholine with a dissociation constant of 6 microM. The lipid-bound NBD-labeled peptide exhibited a red-edge excitation shift in its emission maximum and anisotropy, consistent with insertion of the probe into the motionally restricted, polar environment provided by the bilayer interface. The small Stokes shift of the NBD fluorophore permits electronic energy homotransfer between peptides on the lipid surface and results in depolarization of the NBD emission. At high surface densities of lipid-bound peptide, the anisotropy of the NBD probe was 33% lower than in corresponding samples in which electronic energy homotransfer was prevented by the addition of an unlabeled peptide. The efficiency of energy transfer between probes was not consistent with a random distribution of peptides on the lipid surface, indicating instead the self-association of lipid-bound apoC-II19-39. We propose that the role of this sequence in apoC-II is not only to mediate binding of protein to a lipid surface, but also to stabilize the lipoprotein complexes by associating with other amphipathic helices within apoC-II and with other apolipoproteins.
The amphipathic alpha-helix is a recognised structural motif that is shared by membrane-associating proteins and peptides of diverse function. The aim of this paper is to determine the orientation of an alpha-helical amphipathic peptide on the bilayer surface. We use five amphipathic 18-residue peptide analogues of a class A amphipathic peptide that is known to associate with a bilayer surface. Tyrosine and tryptophan are used as spectroscopic probes to sense local environments in the peptide in solution and when bound to the surface of unilamellar phosphatidylcholine vesicles. In a series of peptides, tryptophan is moved progressively along the sequence from the nonpolar face (positions 3, 7, 4) to the polar face of the peptide (positions 2, 12). The local environment of the tryptophan residue at each position is determined using fluorescence spectroscopy employing quantum yield, and the wavelength of the emission maximum as indicators of micropolarity. The exposure of the tryptophan residues at each site is assessed by acrylamide quenching. On association with vesicles, the tryptophan residues at positions 3, 7 and 14 are in nonpolar water-shielded environments, and the tryptophan at position 12 is in an exposed polar environment. The tryptophan at position 2, which is located near the bilayer-water interface, exhibits intermediate behaviour. Analysis of the second-derivative absorption spectrum confirmed that the tyrosine residue at position 7 is in a nonpolar water-shielded environment in the peptide-lipid complex. We conclude that these class A amphipathic peptides lie parallel to the lipid surface and penetrate no deeper than the ester linkages of the phospholipids.
The fluorescence decay of tryptophan is a sensitive indicator of its local environment within a peptide or protein. We describe the use of frequency domain fluorescence spectroscopy to determine the conformational and environmental changes associated with the interaction of single tryptophan amphipathic peptides with a phospholipid surface. The five 18-residue peptides studied are based on a class A amphipathic peptide known to associate with lipid bilayers. The peptides contain a single tryptophan located at positions 2, 3, 7, 12, or 14 in the sequence. In aqueous solution, the peptides are unstructured and a triple-exponential function is required to fit the decay data. Association of the peptides with small unilamellar vesicles composed of egg phosphatidylcholine reduces the complexity of the fluorescence decays to a double exponential function, with a reduced dependence of the preexponential amplitude on peptide sequence. The data are interpreted in terms of a rotamer model in which the modality and relative proportions of the lifetime components are related to the population distribution of tryptophan chi1 rotamers about the Calpha-Cbeta bond. Peptide secondary structure and the disposition of the tryptophan residue relative to the lipid and aqueous phases in the peptide-lipid complex affect the local environment of tryptophan and influence the distribution of side-chain rotamers. The results show that measurement of the temporal decay of tryptophan emission provides a useful adjunct to other biophysical techniques for investigating peptide-lipid and protein-membrane interactions.
Although fluorescein is a widely used fluorescent probe in the biosciences, the effect of solvent environment on its spectral properties is poorly understood. In this paper we explore the use of fluorescein as a probe of the state of hydrogen bonding in its local environment. This application is based on the observation, originally made by Martin (Chem. Phys. Lett. 35, 105-111, 1975), that the absorption maximum of fluorescein undergoes substantial shifts in organic solvents related to the hydrogen bonding power of the solvents. We have extended this work by studying the spectral properties of the dianion form of the probe in solvent-water mixtures. We show that the magnitude of the shift correlates with the alpha and beta parameters of Kamlet and Taft (J. Am. Chem. Soc. 98, 377-383; 2886-2894, 1976), which provide a scale of the hydrogen bond donor acidities and acceptor basicities, respectively, of the solvents. In solvent-water mixtures, these shifts reflect general effects of the solvents on the hydrogen bonding environment of the fluorescein through water-solvent hydrogen bonding and specific effects due to fluorescein-solvent hydrogen bonding. Indeed, both the absorption and fluorescence properties appear to be dominated by these effects indicating that the spectral shifts of the dianion can be used as an indicator of its hydrogen bonding environment. We discuss the application of fluorescein as a probe of hydrogen bonding in the microenvironment immediately surrounding the fluorophore, and we illustrate the effect with reference to the fluorescein-antifluorescein antibody complex where it appears that antibodies selected during the immune response possess binding sites that are increasingly dehydrated and hydrophobic.
OBJECTIVE: Menopause may be associated with new onset psychiatric symptoms or may exacerbate or heighten preexisting psychiatric problems in women. We present a model center for midlife women, with a multidisciplinary approach to treating this population, and patients' perceptions of satisfaction with treatment received during referral visits to an outpatient psychiatry clinic. DESIGN: In this study, 59 patients were referred from their primary care provider at the midlife center for evaluation by a faculty psychiatrist in an outpatient setting. A brief telephone interview was administered within 1 year of initial evaluation, using items from the Client Satisfaction Questionnaire-8 (CSQ-8) to assess patient satisfaction with psychiatric services received during the referral visits. Findings were based on responses provided by 50 women who were successfully contacted by telephone for the follow-up assessment. RESULTS: For this sample, the mean total client satisfaction score was 27.8 (s = 5.4) of a possible score of 32, which indicated that most women who were referred for psychiatric services reported a positive experience with the services provided by outpatient psychiatrists and reported being very satisfied with their treatment. CONCLUSIONS: We feel that this model center represents a unique way to identify and treat psychiatric disorders in a patient population that may be at high risk for depression and other psychiatric disorders.
The Changes in Sexual Functioning Questionnaire (CSFQ), a structured interview/questionnaire designed to measure illness- and medication-related changes in sexual functioning, is presented with evidence of its validity and reliability. Medical students (n = 122) and psychiatry residents (n = 33) completed the CSFQ on two separate occasions. Residents also completed the Derogatis Interview for Sexual Functioning-Self-Report (DISF-SR), a reliable, validated measure used in research on sexual functioning in patient populations. Concurrent validity was established between the CSFQ and the DISF-SR and test-retest reliability was high. The CSFQ is a reliable and valid measure of sexual functioning, useful in both clinical and research settings.
The Changes in Sexual Functioning Questionnaire (CSFQ), a structured interview/questionnaire designed to measure illness- and medication-related effects on sexual functioning, is presented with initial evidence of its clinical usefulness in differentiating between those who have sexual dysfunction and those who have no dysfunction. Individuals from clinical and nonclinical samples completed the CSFQ. The sample groups were compared on mean scores on the CSFQ and its subscales. Comparative findings indicate that psychiatric patients diagnosed with a mood disorder have significantly lower sexual functioning when compared with nonpsychiatric outpatients, medical students, and psychiatry residents combined. The CSFQ is a useful measure for assessing medication- or illness-related effects on sexual functioning in a systematic way.
Prader-Willi syndrome (PWS) is characterized by hypotonia at birth, hypogonadism, early childhood obesity, and mental deficiency. Hypogonadotropic hypogonadism is a major characteristic of patients with PWS, and it is speculated to be due to hypothalamic insufficiency. Two adult female patients with PWS and no prior history of menses are presented. Both of these patients were treated with fluoxetine for psychopharmacologic management of obsessive features in the form of food preoccupation and hyperphagia or for compulsive behaviors in the form of severe self-injurious behaviors. The two female patients with PWS who had primary amenorrhea developed vaginal bleeding believed to be menses following at least 6 months of treatment with fluoxetine. Mature hypothalamic function is characterized by pulsatile release of gonadotropin-releasing hormone (GnRH) in a critical range of frequency and amplitude. Central nervous system neurotransmitters may modify GnRH secretion. Fluoxetine specifically inhibits the reuptake of serotonin which may impact the hypothalamic-pituitary-ovarian system in female patients with PWS.
We report a case of clomipramine-induced tardive dyskinesia (TD) in the setting of chronic use of dextroamphetamine without prior use of neuroleptics, in which the movements persisted after discontinuation of the clomipramine. Other contributing factors include advanced age, history of alcohol abuse, and concomitant administration of hepatic enzyme inhibitors. Other cases of tricyclic-induced TD have occurred primarily in combination with neuroleptics, have involved antidepressants with antidopaminergic actions, or, as in the present case, have resulted from antidepressants with significant anticholinergic effects (n = 17). Predisposing risk factors and potential mechanisms in the precipitation of dyskinesias are discussed.
The Changes in Sexual Functioning Questionnaire (see Appendix) was developed as a brief clinical and research instrument to measure sexual function changes accompanying illness or the administration of medications. In a pilot study of patients with major depression being treated with paroxetine, the instrument was useful in delineating three groups of patients: patients who reported increased libido without sexual dysfunction, patients who developed anorgasmia with possible spontaneous resolution (medication side effect and development of tolerance), and patients with long-term sexual dysfunction unaffected by the medication. Change scores accurately differentiated global elements, changes associated with specific factors of sexual response, and drug-specific side effects. All patients had a therapeutic response to treatment with experiences of sexual functioning that could be categorized into one of the three groups.