1,720,967 research outputs found
Adaptive evolution of the heat-shock response in the Antarctic psychrophilic ciliate, Euplotes focardii: hints from a comparative determination of the hsp70 gene structure
No full textThe Antarctic psychrophilic ciliate Euplotes focardii manifests a dramatic reduction in the activation of its hsp70 gene in response to a heat-shock, while oxidative and chemical stresses activate the transcription of this gene to appreciable extents. To investigate the genetic causes of this eccentric behaviour
of E. focardii in the hsp70 gene transcription activation, we carried out a comparative structural analysis of this gene between E. focardii and another Antarctic Euplotes, E. nobilii, which manifests a psychrotrophic behaviour and an inducible thermal response. No substantial difference was detected in the organization of the hsp70 5’ promoter region, both species bearing canonical regulatory cis-acting elements deputed to bind
transcriptional trans-activating factors. Adenine-rich elements favouring mRNA degradation were instead detected in the hsp70 3’ regulatory region of E. nobilii, but not in that of E. focardii. These observations lend further support to the hypothesis that the causes of the Euplotes focardii unresponsiveness to thermal stress resides in some structural, or functional modifications of transcriptional trans-activating factors
Combination of two regulatory elements in the Tetrahymena thermophila HSP70-1 gene controls heat shock activation
Full text linkThe induction of heat shock genes (HSPs) is thought to be primarily regulated by heat shock transcription factors (HSFs), which bind target sequences on HSP promoters, called heat shock elements (HSEs). In this study, we investigated the 5 untranslated regions of the Tetrahymena thermophila HSP70-1 gene, and we found, in addition to the canonical and divergent HSEs, multiple sets of GATA elements that have not been reported previously in protozoa. By means of in vivo analysis of a green fluorescent protein reporter transgene driven
by the HSP70-1 promoter, we demonstrate that HSEs do not represent the minimal regulatory elements for heat shock induction, since the HSP70-1 is tightly regulated by both HSE and GATA elements. Electrophoretic mobility shift assay also showed that HSFs are constitutively bound to the HSEs, whereas GATA elements are engaged only after heat shock. This is the first demonstration by in vivo analysis of functional HSE and GATA
elements in protozoa. Furthermore, we provide evidence of a functional link between HSE and GATA elements
in the activation of the heat shock response
Functional and structural correlates of persistent ST elevation after acute myocardial infarction successfully treated by percutaneous coronary intervention
No full textBackground: In the thrombolytic era, persistence of ST-segment elevation was considered a marker of LV aneurysm. ST-segment elevation may still be found persistently elevated after successful primary PCI. Echocardiographic correlates of this finding, however, are still poorly known.
Methods and Results: Eighty-two consecutive patients with first STEMI and successful PCI were divided in patients with persistent ST- segment elevation at discharge (sum of ST > 4 mm) (n=33) and without persistent ST- segment elevation (n=49). Conventional and myocardial contrast echocardiography (MCE) were performed at discharge and at 6 months. At discharge, LV aneurysm was more frequent in persistent ST-elevation patients (30%, p<0.005). Similarly, WMSI was higher (p<0.005) and microvascular damage larger (p<0.005) in patients with persistent ST-segment elevation. At 6 months follow-up, LV volumes were similar in the two groups.
Conclusions: After primary PCI, persistent ST-segment elevation is associated with LV aneurysm formation in 30% of cases, it is not associated with significantly larger LV dilation but with larger microvascular damage and dysfunctioning risk are
Cell cycle-dependent expression of gamma-tubulin in the amicronuclear ciliate Tetrahymena pyriformis
No full textIn ciliates, different microtubular structures are nucleated from diverse Microtubule Organizing
Centers (MTOCs). gamma-Tubulin is a tubulin superfamily member that plays an essential role in
microtubule nucleation at the MTOCs. However, little is known about mechanisms regulating the
activity of gamma-tubulin on different MTOCs and during the cell cycle. In Tetrahymena thermophila, the
alpha- and beta-tubulin expression is regulated mainly at the transcriptional level, and changes in the ratio of polymerized/unpolymerized tubulin dimers lead to an increase or decrease of alpha- and beta-tubulin
transcription. This study deals with the characterization of gamma-tubulin in the amicronuclear ciliate
Tetrahymena pyriformis. Sequence analysis revealed some specific substitutions in nucleotide binding
loops characteristic of the Tetrahymena genus and putative conserved phosphorylation sites
located on the external surface of the gamma-tubulin molecule. gamma-Tubulin expression during the cell cycle, in the presence of microtubular poisons and after deciliation, was also characterized. We found that
gamma-tubulin mRNA levels are correlated with basal body proliferation and gamma-tubulin nuclear localization.
We also found that gamma-tubulin expression changes during anti-microtubular drugs treatment, but does
not changes during reciliation. These findings suggest a relationship between the level of unpolymerized tubulin dimers and gamma-tubulin transcription
Ribosomal cold-adaptation: characterization of the genes encoding the acidic ribosomal P0 and P2 proteins from the Antarctic ciliate Euplotes focardii.
No full textMolecular adaptation at low temperature requires specificities represented mainly by modifications in the gene sequence and consequently in the protein primary structure. To characterize the molecular mechanisms responsible for ribosome cold-adaptation, we compared the ribosomal P0 and P2 genes from the Antarctic ciliate Euplotes focardii with homologous genes from mesophilic organisms, including the ciliates Tetrahymena thermophila and non cold-adapted Euplotes species. This analysis revealed the presence of non synonymous mutations unique to E. focardii. In the P0 protein the mutations produced amino acid substitutions that increased the molecular flexibility that may facilitate a conformational adjustment associated with the interaction with the GTPase center of the large subunit rRNA, and increased the hydrophobicity of the region involved in the interaction with P1/P2 heterodimer, probably to keep associated the ribosomal stalk in the cold. In the P2 protein the mutations produced amino acid substitutions that increased the N-terminus flexibility, which may facilitate interactions with P1 protein in the formation of the heterodimer, and reduced the mobility of the C-terminus, to stabilize the stalk during ribosomal activity. Finally, P proteins appeared to be valid markers for investigating the phylogenetic origin of early eukaryotes
A Novel Robust Heat-inducible Promoter for Heterologous Gene Expression in Tetrahymena thermophila
No full textAn increasing amount of data has revealed the importance of inducible promoters in ciliate research and in ciliate-related industries. However, knowledge about these promoters and related genes is relatively sparse. Here we report a novel inducible promoter from a Tetrahymena cytoplasmic Hsp70 gene member, HSP70-2. The reported promoter was able to induce the endogenous gene up to ∼9000-fold after a short heat shock treatment and this remarkable feature has been retained when a relatively short region of the promoter was introduced into a reporter construct followed by transformation. During the recovery period following a short heat shock, both the mRNA and protein levels of the reporter gene were maintained high up to two hours. A constant heat shock treatment to the transformed cells led to a stabilization of the reporter mRNA up to at least six hours and the reporter protein continued to accumulate up to around three hours. The promoter strength appears to be similar to that of the cadmium-induced metallothionein gene (MTT1) promoter. Therefore, the HSP70-2 promoter represents an attractive alternative for the over-expression of proteins in Tetrahymena, and the promoter-reporter gene construct used in this study is an ideal tool to help in understanding the regulation mechanisms of heat shock genes in ciliates. © 2011 Elsevier GmbH
Thrombus aspiration reduces microvascular obstruction after primary coronary intervention: a myocardial contrast echocardiography substudy of the REMEDIA Trial
No full textOBJECTIVES: The aim of this study was to clarify the role of microembolization in the genesis of microvascular obstruction (MO) after percutaneous coronary intervention (PCI). BACKGROUND: Fifty consecutive patients entered the myocardial contrast echocardiography (MCE) substudy of the REMEDIA (Randomized Evaluation of the Effect of Mechanical Reduction of Distal Embolization by Thrombus Aspiration in Primary and Rescue Angioplasty) trial, which defined the role of a new thrombus-aspirating device in preventing distal microembolization after PCI. METHODS: A total of 25 patients were randomized to be pretreated with thrombus aspiration before PCI of the culprit lesion and 25 received standard PCI. At 24 h, 1 week, and 6 months after PCI, MCE was performed by Sonovue, and real-time imaging was performed by contrast pulse sequencing technology. Regional wall motion score index (WMSI), contrast score index (CSI), endocardial length of wall motion abnormality (WML) and contrast defect (CDL), end-diastolic and end-systolic left ventricular (LV) volumes, and ejection fraction were calculated. RESULTS: At each time point, in patients treated with a thrombus-aspiration filter device, WMSI, CSI, WML, and CDL were significantly lower and ejection fraction higher (p < 0.05 vs. control patients), whereas LV volumes were slightly but not significantly smaller compared with control patients. In the overall study population, the extent of MO significantly correlated with temporal changes in LV volumes. CONCLUSIONS: Thrombus aspiration used at the time of PCI significantly reduces the extent of MO and myocardial dysfunction, although it does not have a significant favorable effect in preventing LV remodeling. Thus, the beneficial effect of thrombus aspiration occurs at the microvascular level, but additional mechanisms may play a role in influencing the final extent of MO, which strictly correlates with post-infarct LV remodeling
Reversible coronary microvascular dysfunction: a common pathogenetic mechanism in Apical Ballooning or Tako-Tsubo Syndrome
No full textAims To study coronary microvascular dysfunction as possible pathogenetic mechanism in Apical Ballooning Syndrome (ABS). Methods and results Fifteen ABS patients (all women, 68 +/- 14 years) underwent myocardial contrast echocardiography at baseline during adenosine infusion (140 microg/kg/min) and at 1-month follow-up and compared with a group of anterior ST-elevation myocardial infarction (STEMI) patients with similar clinical characteristics. Myocardial perfusion was assessed by contrast score index (CSI) and endocardial length of contrast defect (contrast defect length, CDL), whereas myocardial dysfunction by wall motion score index (WMSI), endocardial length of contractile dysfunction (wall motion defect length, WMDL), and LV ejection fraction (LVEF). At baseline, no difference in myocardial perfusion and dysfunction were present between the two groups. During adenosine challenge, while no changes were observed in STEMI group, in ABS patients CSI, CDL, WMSI, and WMDL significantly decreased compared with baseline (P < 0.001 vs. baseline for all parameters) and LVEF significantly increased (P = 0.01 vs. baseline). At 1-month follow-up, myocardial perfusion and dysfunction completely recovered in ABS patients (P < 0.001 vs. baseline for all parameters), whereas no significant changes were observed in STEMI group. Conclusion Our data strongly suggest that in ABS, irrespectively of its underlying aetiology, acute and reversible coronary microvascular vasoconstriction could represent a common pathophysiological mechanism
Images in cardiovascular medicine. Intramyocardial spontaneous hematoma mimicking an acute myocardial infarction.
No full textAn 80-year-old man affected by rheumatoid arthritis and chronic myeloid leukemia who was a smoker and hypertensive was admitted to the coronary care unit for first ST-elevation myocardial infarction. The diagnosis was suspected on the basis of the presence of chest pain associated with ST-segment elevation in leads III and aVF and a cardiac troponin T level of 0.30 ng/dL. At coronary angiography, performed 2 hours after pain onset, a 50% stenosis of the proximal right coronary artery with a translucent filling defect that suggested a parietal thrombus at the cardiac crux was found (see online-only Data Supplement Movie I); the left coronary artery had diffuse atherosclerosis in the absence of significant stenosis. Therefore, no interventional procedure was performed and the patient was treated with aspirin and clopidogrel. The echocardiogram performed soon after coronary catheterization showed an expansive lesion in the basal segment of the inferior wall characterized by echodensity intermediate between blood and tissue (Figure 1A). Myocardial contrast echocardiography documented that the expansive lesion was characterized by a reduced and irregular microvascular network compatible with both hemangioma 1 and intramyocardial hematoma 2 (Figures 1B and 2A; online-only Data Supplement Movies II and III). Magnetic Resonance Imaging further clarified the diagnosis. In fact, T2-weighted fat-suppressed images documented the presence of a hyperintense expansive lesion compatible with both hemangioma and intramyocardial hematoma (Figure 2B), but first-pass perfusion imaging showed marked signal loss in the lesion (Figure 3A), with no enhancement within the first minute (Figure 3B; online-only Data Supplement Movies IV and V). At late enhancement, a mild subendocardial perfusion defect remained only in the midventricular inferior wall. This pattern is typical of intramyocardial hemorrhage, whereas the contrast enhancement pattern of hemangioma is characterized by slow peripheral contrast uptak
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