Nanoclusters and nanolines: the effect of molybdenum oxide substrate stoichiometry on iron self-assembly.

The growth of Fe nanostructures on the stoichiometric MoO2/Mo(110) and oxygen-rich MoO2+x /Mo(110) surfaces has been studied using low-temperature scanning tunnelling microscopy (STM) and density functional theory calculations. STM results indicate that at low coverage Fe nucleates on the MoO2/Mo(110) surface, forming small, well-ordered nanoclusters of uniform size, each consisting of five Fe atoms. These five-atom clusters can agglomerate into larger nanostructures reflecting the substrate geometry, but they retain their individual character within the structure. Linear Fe nanocluster arrays are formed on the MoO2/Mo(110) surface at room temperature when the surface coverage is greater than 0.6 monolayers. These nanocluster arrays follow the direction of the oxide rows of the strained MoO2/Mo(110) surface. Slightly altering the preparation procedure of MoO2/Mo(110) leads to the presence of oxygen adatoms on this surface. Fe deposition onto the oxygen-rich MoO2+x /Mo(110) surface results in elongated nanostructures that reach up to 24 nm in length. These nanolines have a zigzag shape and are likely composed of partially oxidised Fe formed upon reaction with the oxygen-rich surface.

Atomically resolved STM imaging with a diamond tip: simulation and experiment.

The spatial resolution of a scanning tunneling microscope (STM) can be enhanced using light element-terminated probes with spatially localized electron orbitals at the apex atom. Conductive diamond probes can provide carbon atomic orbitals suitable for STM imaging with sub-Ångström lateral resolution and high apex stability crucial for the small tunneling gaps necessary for high-resolution experiments. Here we demonstrate that high spatial resolution can be achieved in STM experiments with single-crystal diamond tips, which are generally only considered for use as probes for atomic force microscopy. The results of STM experiments with a heavily boron-doped, diamond probe on a graphite surface; density functional theory calculations of the tip and surface electronic structure; and first-principles tunneling current calculations demonstrate that the highest spatial resolution can be achieved with diamond tips at tip-sample distances of 3-5 Å when frontier p-orbitals of the tip provide their maximum contribution to the tunneling current. At the same time, atomic resolution is feasible even at extremely small gaps with very high noise in the tunneling current.

Growth and ordering of Ni(II) diphenylporphyrin monolayers on Ag(111) and Ag/Si(111) studied by STM and LEED.

The room temperature self-assembly and ordering of (5,15-diphenylporphyrinato)nickel(II) (NiDPP) on the Ag(111) and Ag/Si(111)-(√3 × âˆš3)R30° surfaces have been investigated using scanning tunnelling microscopy and low-energy electron diffraction. The self-assembled structures and lattice parameters of the NiDPP monolayer are shown to be extremely dependent on the reactivity of the substrate, and probable molecular binding sites are proposed. The NiDPP overlayer on Ag(111) grows from the substrate step edges, which results in a single-domain structure. This close-packed structure has an oblique unit cell and consists of molecular rows. The molecules in adjacent rows are rotated by approximately 17° with respect to each other. In turn, the NiDPP molecules form three equivalent domains on the Ag/Si(111)-(√3 × âˆš3)R30° surface, which follow the three-fold symmetry of the substrate. The molecules adopt one of three equivalent orientations on the surface, acting as nucleation sites for these domains, due to the stronger molecule-substrate interaction compared to the case of the Ag(111). The results are explained in terms of the substrate reactivity and the lattice mismatch between the substrate and the molecular overlayer.

Elevated levels of some neuroactive progesterone metabolites, particularly isopregnanolone, in women with chronic fatigue syndrome.

Chronic fatigue syndrome (CFS) is a controversial entity whose cause is unknown. In this study we have explored the possibility that progesterone metabolites may be involved. Plasma levels of the progesterone precursor pregnenolone, progesterone itself, and five ring A-reduced metabolites of progesterone were measured in 20 women with CFS and in 13 age-matched controls. To minimize the contribution of the ovary, women were either post-menopausal or in the follicular phase of the menstrual cycle (day 4-8), and progesterone levels were all well within the expected range (< or = 3.5 nmol/l). Mean values for progesterone and all of its metabolites were higher in CFS patients, the most marked being a 2.3-fold elevation in isopregnanolone (3beta,5alpha-tetrahydroprogesterone; p < or = 0.001). Progesterone levels were correlated with those of its metabolites, but even after controlling for progesterone by ANCOVA, isopregnanolone levels were still elevated (p < or = 0.001). These elevated levels of isopregnanolone could not be attributed to medications (antidepressants and anxiolytics). When the CFS patients were divided into two groups according to their Hamilton depression scale ratings, mean (+/-SD) isopregnanolone levels were higher (274+/-160 vs 197+/-119 pmol/l) in the less depressed group (ratings 2-14) than in the more depressed group (ratings 17-28), although this difference did not reach significance. Progesterone levels were negatively correlated with Hamilton depression rating scores (r=-0.56; p<0.01). These results suggest that increases in ring A-reduced progesterone metabolites, particularly isopregnanolone, are associated with CFS, and that the pathophysiology of CFS is unlikely to be due to depression.

Neuroactive ring A-reduced metabolites of progesterone in human plasma during pregnancy: elevated levels of 5 alpha-dihydroprogesterone in depressed patients during the latter half of pregnancy.

Progesterone and its 5 alpha reduced metabolite, 5 alpha-dihydroprogesterone, rise greatly in pregnancy. Both are known to have anesthetic properties, as do a number of other ring A-reduced progesterone metabolites. The possible significance of these steroids with respect to the mood changes that are common in pregnancy and in the puerperium has not been explored. In this study, pregnenolone, progesterone, and five neuroactive progesterone metabolites: the 5 alpha and 5 beta dihydroprogesterones (DHP), and three tetrahydroprogesterones (THP)-3 alpha,5 alpha-THP, 3 beta,5 beta-THP, and 3 beta,5 alpha-THP-were studied at various stages of pregnancy and in the early postpartum period. Levels of all of the steroids rose greatly during pregnancy (P < 0.001), being highest for progesterone (562-fold the follicular level), 5 alpha-DHP (161-fold), 3 beta,5 alpha-THP (56-fold), 3 alpha,5 alpha-THP (37-fold), pregnenolone (30-fold), 5 beta-DHP (16-fold) and 3 beta,5 beta-THP (16-fold) at 37 wk of gestation. During the period 2-7 d postpartum, the level of progesterone fell precipitously, whereas those of pregnenolone and the metabolites fell more slowly and mean levels were still elevated compared with follicular levels 2 wk after delivery. By 7 wk postpartum, only 3 alpha,5 alpha-tetrahydroprogesterone and 3 beta,5 beta-tetrahydroprogesterone remained slightly elevated (P < or = 0.012 and 0.007, respectively). Mean levels of the progesterone metabolites tended to be higher in depressed patients compared with controls, and this difference reached significance for 5 alpha-dihydroprogesterone both at 27 wk (P = 0.04) and at 37 wk (P = 0.02) of gestation (combined, P = 0.003). These results show that all five of these metabolites rise markedly during pregnancy and suggest that alterations in progesterone metabolites may be involved in the mood changes of pregnancy and the puerperium.

Determination of progesterone and some of its neuroactive ring A-reduced metabolites in human serum.

A method for the separation and assay of some ring A-reduced metabolites of progesterone (pregnanediones and pregnanolones) is described. Serum was extracted with an organic solvent, and the extract chromatographed using high performance liquid chromatography (HPLC). A total of 50 fractions was collected for each sample and split using a stream splitter so that 30% was collected in counting vials for recovery while 70% was collected in test tubes which were assayed by radioimmunoassay. An antiserum raised in our laboratory to progesterone-3-CMO-BSA cross-reacted with five of these compounds (5alpha- and 5beta-dihydroprogesterone, 3alpha- and 3beta-5alpha-tetrahydroprogesterone, and 3beta, 5beta-tetrahydroprogesterone). Since pregnenolone eluted with 5alpha, 3beta-tetrahydroprogesterone, pregnenolone was assayed separately and its effect subtracted. Using this method it was shown that picogram to nanogram/ml amounts of these metabolites are present in all human sera. Levels in men were comparable to those of women in the follicular phase of the menstrual cycle. 5alpha-Dihydroprogesterone and 3alpha,5alpha-tetrahydroprogesterone rose substantially in the luteal phase of the menstrual cycle and all rose considerably during pregnancy.

Efficacy of light versus tryptophan therapy in seasonal affective disorder.

BACKGROUND: Although light therapy has become the accepted treatment for patients suffering from seasonal affective disorder (SAD, winter depression), almost 40% of these patients do not respond, and require an alternative treatment. METHODS: The therapeutic effects of light versus tryptophan on SAD were studied in a repeated measures design in 13 SAD patients (11 women, 2 men). Light therapy for 2 weeks or tryptophan for 4 weeks was given, separated by a one week washout period. All were assessed with the modified Hamilton Depression Rating scale (SIGH-SAD) at the beginning and end of each treatment. RESULTS: Four (31%) of the patients did not respond to either therapy. Four tryptophan-resistant patients responded to light therapy, while one light therapy-resistant patient responded to tryptophan. Relapse occurred rapidly after stopping light therapy but not after stopping tryptophan therapy. CONCLUSIONS: There were significant therapeutic effects of both light (p = 0.012) and tryptophan (p = 0.014) on SAD, which were not significantly different from each other. There may be a time difference between the residual pharmacokinetic effects after stopping therapy. LIMITATIONS: The groups studied were small. This was an open study. CLINICAL RELEVANCE: Tryptophan was equally effective to light therapy in treating SAD, but relapse after withdrawal of tryptophan probably occurs more slowly.

Neuroendocrine responses to inhibitors of steroid biosynthesis in patients with major depression resistant to antidepressant therapy.

OBJECTIVE: Patients with major depression frequently have high cortisol levels and resistance to dexamethasone. We sought to determine to what extent major depression might be influenced by inhibitors of steroid biosynthesis and to study the endocrine changes produced. METHOD: After drug washout, 20 treatment-resistant patients with major depression were given aminoglutethimide, metyrapone, and/or ketoconazole, along with a small dose of cortisol for 8 weeks. Hamilton Depression Rating Scale (HDRS) ratings, 8:00 AM cortisol dehydroepiandrosterone sulfate (DHAS), adrenocorticotropin (ACTH), and testosterone levels were followed weekly or oftener. A dexamethasone suppression test (DST) was conducted before and after treatment. RESULTS: Seventeen patients (85%) completed the course of treatment, and a significant mean drop (P < or = 0.0001) of 50% in the HDRS score occurred by 7 weeks of treatment. Cortisol levels fluctuated widely and were often still high after the patient had improved clinically. Dehydroepiandrosterone sulfate levels fell more uniformly and were found to be a useful indicator of compliance and, to some extent, efficacy with aminoglutethimide and ketoconazole therapy. The correlation between DHAS and HDRS (r = 0.94) was significant (P = 0.02). Testosterone levels in men fell with ketoconazole but returned promptly to normal at the end of treatment. Adrenocorticotropin levels were normal or elevated, depending on the assay used, and rose (P = 0.07; n = 13) in most subject during therapy. Of the 6 responders who had nonsuppressor DSTs before starting therapy, 5 had reverted to normal 1 to 2 weeks following cessation of therapy (P = 0.0006). CONCLUSIONS: Abnormal metabolism of adrenocortical steroids may perpetuate depression, and alterations of synthesis or metabolism of these steroids may lead to a remission.

Metabolism of progesterone by human lymphocytes: production of neuroactive steroids.

Although it has long been recognized that lymphocytes have the capacity to reduce cortisol at the C3, C5, and C20 positions, the specificity and the physiological variation of these reactions have received little attention. We have shown that such reactions also occur with progesterone. Lymphocytes were isolated from whole blood using Percoll density gradient centrifugation. The cells were incubated for 20 h with tritiated progesterone as radioactive tracer. After extractions into ethyl acetate, the residue was subjected to high performance liquid chromatography, and the radioactivities of the separated compounds were determined. Without cells, 95-97% of the tracer added was recovered in the progesterone peak, while in the presence of 4 x 10(6) lymphocytes, this was reduced to 45-90%. The metabolites obtained included at least 10 different compounds, including those corresponding in their retention times to the neuroactive 5 alpha and 5 beta dihydroprogesterones and their 3 alpha- and 3 beta- tetrahydroprogesterone derivatives. The conversion decreased with the addition of other steroids such as testosterone, cortisol, and corticosterone, suggesting that these steroids are metabolized by the same enzymes. When the cells from two pregnant patients were combined and incubated with tracer, and with and without nonradioactive progesterone, no peaks were detected by two progesterone radioimmunoassays in the absence of added nonradioactive progesterone, while in its presence three peaks corresponding to 5 alpha-dihydroprogesterone, 3 alpha-hydroxy-5 alpha-pregnane-20-dione and 3 beta-hydroxy-5 alpha-pregnane-20-dione eluted before the P peak. Their identities were confirmed using the two different progesterone radioassays that cross-reacted with these metabolites. The highest mean conversion (44.7% +/- 3.2 SE) was found with the lymphocytes of pregnant women and with that of one lactating woman (50%). Conversions by lymphocytes of women in the follicular phase (29.3% +/- 1.3 SE) were significantly lower than those in pregnancy (P = 0.014) but did not differ significantly (P > or = 0.05) from those of women in the luteal phase (22.2% +/- 3.4 SE), those of postmenopausal women (23.5% +/- 4.9 SE), or of men (22.5% +/- 2.4 SE). Lymphocytes appear to provide a hitherto unrecognized but possibly important source of neuroactive steroids.

Antiglucocorticoid therapies in major depression: a review.

In major depression there are two well-documented biochemical abnormalities: hypercortisolism, and its resistance to dexamethasone suppression. It therefore seems reasonable to see if giving drugs which interfere with cortisol biosynthesis might bring about a remission. An open trial was begun in our institution of 20 refractory patients with major depression. Aminoglutethimide, metyrapone, ketoconazole or combinations of these drugs along with a maintenance dose of cortisol were used for eight weeks. Of the 17 completers, eleven patients were considered to have good responses and two partial responses. Four had complete remissions lasting several years. A similar study of four patients who received oral RU 486 also gave encouraging results. Two patients with obsessive compulsive disorder associated with depression showed striking improvement on aminoglutethimide combined with a serotonin re-uptake inhibitor. In addition to a case report in 1988 by Ravaris et al. of a patient hypophysectomized for previous Cushing's syndrome whose depression responded to ketoconazole, several other studies over the past five years have had similar favorable results. Wolkowitz et al. (1993) gave oral ketoconazole to 10 depressed patients for three weeks which resulted in a significant drop in their Hamilton Depression Scale ratings. O'Dwyer et al. (1995) conducted a placebo-controlled single-blind crossover study using lifetyrapone and maintenance cortisol in eight inpatients for two weeks; six responded. Thakore and Dinan (1995) studied eight inpatients using ketoconazole for four weeks; there were five responders and three partial responders. Anand et al. (1995) conducted a four-week double-blind trial of ketoconazole in a single treatment-refractory patient with good results. Arana et al. (1995) used a different approach but one which also leads to suppression of endogenous corticosteroids-i.e. short-term dexamethasone suppression (4 mg/day for four days). When tested at 14 days, 7/19 of the dexamethasone group had responded well while only 1/18 of the placebo group had responded. While these studies have shortcomings, antiglucocorticoid therapy appears to be an effective tool in the treatment of major depression. Possible mechanisms are discussed, and a unifying hypothesis is attempted.

Potentiation of fluoxetine by aminoglutethimide, an adrenal steroid suppressant, in obsessive-compulsive disorder resistant to SSRIs: a case report.

1. The role of serotonin in the aetiology of obsessive compulsive disorder (OCD) has been established through considerable indirect evidence (Landry and Chouinard, 1990). The strongest evidence comes from the fact that drugs known to be serotonin-selective reuptake inhibitors (SSRIs) have been found to be useful in the pharmacotherapy of OCD (Landry and Chouinard, 1990). 2. The authors investigated a new treatment approach by adding an adrenal steroid suppressant to a SSRI, fluoxetine, in the case of a severe obsessive-compulsive patient who was drug-resistant to clomipramine and SSRIs. 3. We found that the combination of aminoglutethimide 250 mg qid and fluoxetine 40 mg die significantly improved the patient's condition. Moreover, during a four and a half year period, each time we tried to decrease either fluoxetine or the steroid suppressant, the patient started to relapse, suggesting that the adrenal steroid suppressant had a potentiating effect on the SSRI.

The psychotropic effects of inhibitors of steroid biosynthesis in depressed patients refractory to treatment.

Twenty patients, diagnosed as suffering from treatment-resistant major depression, were treated with one or more drugs that decrease corticosteroid biosynthesis. Nine were psychotic, 11 nonpsychotic. Seventeen completed the treatment (8 psychotic, 9 nonpsychotic); 13 responded (5 psychotic, 8 nonpsychotic; 11 responded completely (i.e., a drop in the Hamilton Depression Scale of at least 50%, to < or = 15), and 2 responded partially. The mean age of the responders (45.2 +/- 12.6 years) did not differ significantly from that of the nonresponders (48.7 +/- 12/3). Data were analyzed in the following categories; (1) the presence or absence of psychosis, (2) response or nonresponse to treatment, and (3) the drug(s) used (aminoglutethimide, ketoconazole, or a combination of either of these with metyrapone). The patients improved over time on the Hamilton Depression Scale independent of the medication used. Responders demonstrated improvement in mood, insomnia, anxiety, diurnal variation, paranoia and obsessive compulsiveness. Nonpsychotics responded better than psychotics.

Possible use of glucocorticoid receptor antagonists in the treatment of major depression: preliminary results using RU 486.

The rationale for the use of anti-glucocorticoids in the treatment of major depression has been reviewed. Four patients with chronic severe depression who were resistant to conventional therapies were given RU 486 (200 mg/day) for periods up to eight weeks. Substantial levels of RU 486 were achieved within the first few days, and the levels fell gradually over the week after the treatment was discontinued. In three cases, treatment was stopped before the eight weeks were completed: in one case because of the appearance of a rash, in the others because of side-effects, which, in retrospect, were likely unrelated to the drug. The mean scores on the Hamilton Rating Scale for Depression of three patients decreased. Levels of adrenocorticotrophin, dehydroepiandrosterone and cortisol rose during treatment. These preliminary results suggest that glucocorticoid antagonists may be effective in the treatment of major depression and merit further exploration.

Can further benefit be achieved by adding flosequinan to patients with congestive heart failure who remain symptomatic on diuretic, digoxin, and an angiotensin converting enzyme inhibitor? Results of the flosequinan-ACE inhibitor trial (FACET).

BACKGROUND: Angiotensin converting enzyme inhibitors, diuretics, and digoxin are each effective in treating congestive heart failure, but many patients remain symptom-limited on all three medications. This trial was designed to determine whether the addition of oral flosequinan, a new direct-acting arterial and venous vasodilator with possible dose-dependent positive inotropic effects, improves exercise tolerance and quality of life in such patients. METHODS AND RESULTS: In a randomized, double-blind multicenter trial, 322 patients with predominantly New York Heart Association class II or III congestive heart failure and left ventricular ejection fractions of 35% or less, who were stabilized on a diuretic, angiotensin converting enzyme inhibitor, and digoxin, were treated with 100 mg flosequinan once daily, 75 mg flosequinan twice daily, or matching placebo. Efficacy was evaluated with serial measurements of treadmill exercise time, responses to the Minnesota Living With Heart Failure Questionnaire (LWHF), and clinical assessments during a baseline phase and a 16-week treatment period. After 16 weeks, 100 mg flosequinan once daily produced a significant increment in median exercise time (64 seconds at 16 weeks) compared with placebo (5 seconds), whereas the higher-dose flosequinan group did not show a statistically significant increase. Flosequinan (100 mg once daily) also improved the overall LWHF score significantly compared with placebo; both active therapies decreased the physical component, but 75 mg flosequinan twice daily was associated with a trend toward worsening of the emotional component. Most clinical assessments tended to improve on active therapy. CONCLUSIONS: These results indicate that additional symptomatic benefit can be attained by adding flosequinan to a therapeutic regimen already including a converting enzyme inhibitor. Because in the future most patients will fall into this category, flosequinan is a potential adjunctive agent in the management of severe congestive heart failure. However, because recent evidence indicates that the flosequinan dose studied in the present trial has an adverse effect on survival, the benefit-to-risk ratio must be assessed in individual patients.

Effect of maternal serum on viability and function of early human placental explants.

Fetal bovine serum (FBS) is frequently used to supplement chemically defined media such as Ham's F10 when studying placental explant cultures. However in vitro production of hormones is usually declining by the 2nd or 3rd day and is short-lived (7 to 10 days). In this study we explored the use of human maternal serum (HMS) from early gestation as the medium supplement to Ham's F10. Early placental hormone production was compared using two concentrations of FBS and HMS. On Day 3 of incubation, progesterone production in 10% HMS was 12-fold increased over that in 10% FBS, estradiol production was increased 10-fold, and beta hCG production more than 3-fold. When the serum concentrations were increased to 40%, the results in all cases were similar to those at 10%. Preliminary characterization studies revealed that the stimulatory activity of HMS is heat-labile, neither extractable into organic solvent (diethyl ether) nor dialyzable, suggesting that it is protein in nature. In a long-term incubation, compared with FBS (7 days), HMS permitted survival of culture up to 30 days, judged both histologically and biochemically. We conclude that HMS provides substance(s), probably protein in nature, not present in FBS or non-pregnant human serum, which are important for human placental viability and function in vivo.

Effect of maternal serum on viability and function of early human placental explants.

Fetal bovine serum (FBS) is frequently used to supplement chemically defined media such as Ham's F10 when studying placental explant cultures. However in vitro production of hormones is usually declining by the 2nd or 3rd day and is short-lived (7 to 10 days). In this study we explored the use of human maternal serum (HMS) from early gestation as the medium supplement to Ham's F10. Early placental hormone production was compared using two concentrations of FBS and HMS. On Day 3 of incubation, progesterone production in 10% HMS was 12-fold increased over that in 10% FBS, estradiol production was increased 10-fold, and ßhCG production more than 3-fold. When the serum concentrations were increased to 40%, the results in all cases were similar to those at 10%. Preliminary characterization studies revealed that the stimulatory activity of HMS is heat-labile, neither extractable into organic solvent (diethyl ether) nor dialyzable, suggesting that it is protein in nature. In a long-term incubation, compared with FBS (7 days), HMS permitted survival of culture up to 30 days, judged both histologically and biochemically. We conclude that HMS provides substance(s), probably protein in nature, not present in FBS or non-pregnant human serum, which are important for human placental viability and function in vivo.