The metal reductase activity of some multiheme cytochromes c: NMR structural characterization of the reduction of chromium(VI) to chromium(III) by cytochrome c(7)

The redox reaction between CrO(4)(2-) and the fully reduced three-heme cytochrome c(7) from Desulfuromonas acetoxidans to give chromium(III) and the fully oxidized protein has been followed by NMR spectroscopy. The hyperfine coupling between the oxidized protein protons and chromium(III), which remains bound to the protein, gives rise to line-broadening effects on the NMR resonances that can be transformed into proton-metal distance restraints. Structure calculations based on these unconventional constraints allowed us to demonstrate that chromium(III) binds at a unique site and to locate it on the protein surface. The metal ion is located 7.9 +/- 0.4 A from the iron of heme IV, 16.3 +/- 0.7 A from the iron of heme III, and 22.5 +/- 0.5 A from the iron of heme I. Shift changes caused by the presence of unreactive MoO(4)(2-), a CrO(4)(2-) analogue, indicate the involvement of the same protein area in the anion binding. The titration of the oxidation of cytochrome c(7) shows a detailed mechanism of action. The presence of a specific binding site supports the hypothesis of the biological role of this cytochrome as a metal reductase.     

Residual symptoms in depression: an emerging therapeutic target

Residual symptoms, despite successful response to therapy, appear to be the rule in unipolar depression. Most of the residual symptoms occur in the prodromal phase of illness. Residual symptoms are associated with biological correlates, mainly involving the hypothalamic-pituitary-adrenal (HPA) axis and the sleep architecture. They are powerful predictors of relapse. These findings have led to the hypothesis that residual symptoms upon recovery may progress to become prodromal symptoms of relapse. A sequential strategy (encompassing pharmacotherapy in the acute phase of illness and cognitive behavioral therapy in its residual phase) has been developed and was found to be effective in decreasing relapse rate in controlled studies. A largely untested assumption in unipolar depression is that pharmacological strategies that are effective in the short term are the most suitable for postacute and residual phases or maintenance. The literature on subclinical symptomatology calls for specific, stage-oriented, therapeutic approaches. The efficacy of antidepressant drugs may be assessed not only on differential remission rates, but also on differential amount of residual symptomatology after response.     

Oculomotor impairment after 1 night of total sleep deprivation: a dissociation between measures of speed and accuracy.

OBJECTIVES: The present study examined the effects of 40 h of sleep deprivation and of time-of-day on saccadic and smooth pursuit oculomotor performance. METHODS: Nine normal subjects slept for 3 consecutive nights in the laboratory (one adaptation, one baseline, one recovery). Baseline and recovery were separated by a period of 40 h of continuous wakefulness, during which subjects were tested every 2 h. Oculomotor performance assessed at the following hours: 10:00, 12:00, 14:00, 16:00, 18:00, 20:00, 22:00, of both the days preceding and following the sleep deprivation night, as well as at 24:00, 02:00, 04:00, 06:00 and 08:00 h during the deprivation period. RESULTS: Saccade latency increased and peak velocity decreased significantly during the post-deprivation day; saccadic accuracy was unaffected. As regards smooth pursuit performance, phase (a measure of accuracy) was not affected by sleep loss, while velocity gain significantly decreased during the day that followed the sleep deprivation night. Significant time-of-day effects on the considered oculomotor variables except saccadic accuracy were also found, indicating an overall performance impairment during the night. CONCLUSIONS: It is concluded that 40 h of sleep deprivation significantly impaired diurnal performance in pursuit and saccadic tasks. This performance worsening is limited to the measures of speed, while accuracy is not affected by sleep loss. A significant operational relevance of these results is suggested, since saccadic velocity has recently been found to be negatively correlated with simulator vehicle crash rates.     

Physiological cyclic variation of the myocardial integrated backscatter signal in athlete's heart

BACKGROUND: Left ventricular hypertrophy which realizes in athlete's heart could create some problems of acoustic reflection related to the increase of myocytic and not-myocytic elements of the heart. The aim of the present study was to analyze the ultrasonic backscatter myocardial indexes both as peak end-diastolic signal intensity and as its cardiac-cyclic variation in athlete's heart, compared to healthy sedentary controls. METHODS: Two groups of ten subjects each, all males of mean age (31.6+/-3.5), and of comparable weight and height were analyzed: group (A) comprised ten cyclists of good professional level and group (C) included ten healthy subjects acting as controls. A 2D-color Doppler echocardiography with a digital echograph Agilent Technologies (AT) Sonos 5500 was carried out on all subjects in the study for the conventional analysis of the left ventricular mass and function. The ultrasonic myocardial integrated backscatter signal (IBS) was analyzed with an "Acoustic Densitometry" module implemented on an AT echograph. The signal was also sampled with a R.O.I. placed at interventricular septum and at posterior left ventricular wall level. The systo-diastolic variation of the backscatter was also considered as Cyclic Variation Index (CVIibs). RESULTS: The left ventricular mass was significantly higher in athletes in comparison with controls (LVMbs: A: 154.5+/-18.7; C: 101.4+/-12.4; p<0.001). The end diastolic IBS signal did not show significant statistical differences between the two groups. The CVIibs both at septum (A: 30.5+/-5.3; C: 27.2+/-7.3; p<0.002) and posterior wall level (A: 43.7+/-9.1; C: 40.7+/-9.1; p<0.001) though was comparable in both groups. CONCLUSION: The conclusions reached in the present study confirmed the physiology of the left ventricular hypertrophy of the athlete's heart evaluated with an ultrasonic integrated backscatter tissue characterization, in particular through the cyclic variation of integrated backscatter myocardial signal. This finding is probably the expression of a preserved intramural myocardial function in the athlete's heart despite the increase of left ventricular mass induced by physical training.     

The T9176G mtDNA mutation severely affects ATP production and results in Leigh syndrome

The authors identified a novel mtDNA mutation (T9176G) in the ATPase 6 gene in a family in which a 10-year-old girl had a severe neurodegenerative disorder, her elder sister had died of Leigh syndrome (LS), and a maternal uncle had a spinocerebellar disorder. Biochemical studies disclosed a reduced rate of ATP synthesis in skin fibroblast cultures from the proposita as the likely explanation of her severe illness. The findings expand the genetic variants associated with LS.     

Strategies for cytokine utilisation in tumor therapy

The state of the art with regard to the employment of various cytokine-based tumor immunotherapy strategies and their mechanisms of action are critically reviewed. As matters now stand, adoptive transfer of LAK cells or tumor infiltrating lymphocytes together with high doses of IL-2 constitutes the only immunologic way to hinder tumor growth in advanced stages of cancer. On the other hand, many experimental data show that the local presence of cytokines, either injected repeatedly at tumor site or released by cytokine-gene engineered tumor cells, arouses immunogenicity in apparently nonimmunogenic spontaneous tumors. By strengthening the notion that most tumors are potentially immunogenic, these f'mdings offer substantial evidence to stres~ the potential use ofcytoklnes as a component of new tumor vaccines.     

Effects of indomethacin and ibuprofen on mesenteric and renal blood flow in preterm infants with patent ductus arteriosus

OBJECTIVE: To evaluate the effect of intravenous ibuprofen and indomethacin for treatment of patent ductus arteriosus (PDA) on mesenteric and renal blood flow velocity in preterm infants. STUDY DESIGN: Seventeen mechanically ventilated preterm infants (<33 weeks' gestation) with PDA received either 0.2 mg/kg indomethacin (n = 8) or 10 mg/kg ibuprofen (n = 9), infused over 15 minutes. Mesenteric and renal blood flow velocity were measured by using Doppler ultrasonography. RESULTS: Indomethacin caused a significant reduction in mesenteric and renal blood flow velocity 30 minutes after drug administration; mesenteric and renal blood flow velocity did not return to the pretreatment values by 120 minutes. Ibuprofen did not alter blood flow 30 minutes after treatment, and blood flow increased 120 minutes after treatment. Mesenteric and renal blood flow velocity changes were significantly different between the 2 treatment groups. CONCLUSIONS: Compared with indomethacin, ibuprofen did not significantly reduce mesenteric and renal blood flow velocity.     

Inv(16) acute myeloid leukemia cells show an increased sensitivity to cytosine arabinoside in vitro

Abstract: Karyotype represents the major independent prognostic factor for response and remission duration in acute leukemia. In particular, it has been reported that acute myeloid leukemia (AML) patients with inv(16) abnormality show a better prognosis, especially in case of treatment with high-dose Ara-C (HD Ara-C) containing regimens. In this study we aimed at testing whether leukemic cells from patients showing the inv(16) were more sensitive to Ara-C in vitro, compared to AML blasts from patients with normal karyotype or chromosomal abnormalities other than t(15;17) or t(8;21). We analyzed blast cells from 30 patients who were diagnosed and treated in our institution. The IC₅₀ of Ara-C, as tested by the XTT colorimetric assay, was significantly lower in cases with inv(16) (18.5±15.88 μmol/l vs. 38±14.6 μmol/l, in cases with other abnormalities, p = 0.01). This result was confirmed by a higher incorporation of [³H]-Ara-C into DNA (p = 0.02 and p = 0.001 compared to samples with normal and abnormal karyotype, respectively). All the same, Ara-C induced apoptosis was significantly increased in cells from patients with inv(16). Our data suggest a possible interaction between the molecular background of inv(16) and a modification of intracellular metabolism of Ara-C, and could thus provide a rationale for HD-Ara-C-based schedules for patients with inv(16) AML.