Occludin, caveolin-1, and Alix form a multi-protein complex and regulate HIV-1 infection of brain pericytes.

HIV-1 enters the brain by altering properties of the blood-brain barrier (BBB). Recent evidence indicates that among cells of the BBB, pericytes are prone to HIV-1 infection. Occludin (ocln) and caveolin-1 (cav-1) are critical determinants of BBB integrity that can regulate barrier properties of the BBB in response to HIV-1 infection. Additionally, Alix is an early acting endosomal factor involved in HIV-1 budding from the cells. The aim of the present study was to evaluate the role of cav-1, ocln, and Alix in HIV-1 infection of brain pericytes. Our results indicated that cav-1, ocln, and Alix form a multi-protein complex in which they cross-regulate each other's expression. Importantly, the stability of this complex was affected by HIV-1 infection. Modifications of the complex resulted in diminished HIV-1 infection and alterations of the cytokine profile produced by brain pericytes. These results identify a novel mechanism involved in HIV-1 infection contributing to a better understanding of the HIV-1 pathology and the associated neuroinflammatory responses.

Acetylation regulates the stability of a bacterial protein: growth stage-dependent modification of RNase R.

RNase R, an Escherichia coli exoribonuclease important for degradation of structured RNAs, increases 3- to 10-fold under certain stress conditions, due to an increased half-life for this usually unstable protein. Components of the trans-translation machinery, tmRNA, and its associated protein, SmpB, are essential for RNase R instability. However, it is not understood why exponential phase RNase R is unstable or how it becomes stabilized in stationary phase. Here, we show that these phenomena are regulated by acetylation catalyzed by YfiQ protein. One residue, Lys544, is acetylated in exponential phase RNase R, but not in the stationary phase protein, resulting in tighter binding of tmRNA-SmpB to the C-terminal region of exponential phase RNase R and subsequent proteolytic degradation. Removal of the positive charge at Lys544 or a negative charge in the C-terminal region likely disrupts their interaction, facilitating tmRNA-SmpB binding. These findings indicate that acetylation can regulate the stability of a bacterial protein.

Creating a chimeric clathrin heavy chain that functions independently of yeast clathrin light chain.

Clathrin facilitates vesicle formation during endocytosis and sorting in the trans-Golgi network (TGN)/endosomal system. Unlike in mammals, yeast clathrin function requires both the clathrin heavy (CHC) and clathrin light (CLC) chain, since Chc1 does not form stable trimers without Clc1. To further delineate clathrin subunit functions, we constructed a chimeric CHC protein (Chc-YR) , which fused the N-terminus of yeast CHC (1-1312) to the rat CHC residues 1318-1675, including the CHC trimerization region. The novel CHC-YR allele encoded a stable protein that fractionated as a trimer. CHC-YR also complemented chc1Δ slow growth and clathrin TGN/endosomal sorting defects. In strains depleted for Clc1 (either clc1Δ or chc1Δ clc1Δ), CHC-YR, but not CHC1, suppressed TGN/endosomal sorting and growth phenotypes. Chc-YR-GFP (green fluorescent protein) localized to the TGN and cortical patches on the plasma membrane, like Chc1 and Clc1. However, Clc1-GFP was primarily cytoplasmic in chc1Δ cells harboring pCHC-YR, indicating that Chc-YR does not bind yeast CLC. Still, some partial phenotypes persisted in cells with Chc-YR, which are likely due either to loss of CLC recruitment or chimeric HC lattice instability. Ultimately, these studies have created a tool to examine non-trimerization roles for the clathrin LC.

Combined functions of two RRMs in Dead-end1 mimic helicase activity to promote nanos1 translation in the germline.

Dead-end1 (Dnd1) expression is restricted to the vertebrate germline where it is believed to activate translation of messenger RNAs (mRNAs) required to protect and promote that unique lineage. Nanos1 is one such germline mRNA whose translation is blocked by a secondary mRNA structure within the open reading frame (ORF). Dnd1 contains a canonical RNA recognition motif (RRM1) in its N-terminus but also contains a less conserved RRM2. Here we provide a mechanistic picture of the nanos1 mRNA-Dnd1 interaction in the Xenopus germline. We show that RRM1, but not RRM2, is required for binding nanos1. Similar to the zebrafish homolog, Xenopus Dnd1 possesses ATPase activity. Surprisingly, this activity appears to be within the RRM2, different from the C-terminal region where it is found in zebrafish. More importantly, we show that RRM2 is required for nanos1 translation and germline survival. Further, Dnd1 functions as a homodimer and binds nanos1 mRNA just downstream of the secondary structure required for nanos1 repression. We propose a model in which the RRM1 is required to bind nanos1 mRNA while the RRM2 is required to promote translation through the action of ATPase. Dnd1 appears to use RRMs to mimic the function of helicases.

Reversible acetylation on Lys501 regulates the activity of RNase II.

RNase II, a 3' to 5' processive exoribonuclease, is the major hydrolytic enzyme in Escherichia coli accounting for ∼90% of the total activity. Despite its importance, little is actually known about regulation of this enzyme. We show here that one residue, Lys501, is acetylated in RNase II. This modification, reversibly controlled by the acetyltransferase Pka, and the deacetylase CobB, affects binding of the substrate and thus decreases the catalytic activity of RNase II. As a consequence, the steady-state level of target RNAs of RNase II may be altered in the cells. We also find that under conditions of slowed growth, the acetylation level of RNase II is elevated and the activity of RNase II decreases, emphasizing the importance of this regulatory process. These findings indicate that acetylation can regulate the activity of a bacterial ribonuclease.

How RNase R Degrades Structured RNA: ROLE OF THE HELICASE ACTIVITY AND THE S1 DOMAIN.

RNase R, a ubiquitous 3' exoribonuclease, plays an important role in many aspects of RNA metabolism. In contrast to other exoribonucleases, RNase R can efficiently degrade highly structured RNAs, but the mechanism by which this is accomplished has remained elusive. It is known that RNase R contains an unusual, intrinsic RNA helicase activity that facilitates degradation of duplex RNA, but how it stimulates the nuclease activity has also been unclear. Here, we have made use of specifically designed substrates to compare the nuclease and helicase activities of RNase R. We have also identified and mutated several residues in the S1 RNA-binding domain that are important for interacting with duplex RNA and have measured intrinsic tryptophan fluorescence to analyze the conformational changes that occur upon binding of structured RNA. Using these approaches, we have determined the relation of the RNA helicase, ATP binding, and nuclease activities of RNase R. This information has been combined with a structural analysis of RNase R, based on its homology to RNase II, whose structure has been determined, to develop a detailed model that explains how RNase R digests structured RNA and how this differs from its action on single-stranded RNA.

The Helicase Activity of Ribonuclease R Is Essential for Efficient Nuclease Activity.

RNase R, which belongs to the RNB family of enzymes, is a 3' to 5' hydrolytic exoribonuclease able to digest highly structured RNA. It was previously reported that RNase R possesses an intrinsic helicase activity that is independent of its ribonuclease activity. However, the properties of this helicase activity and its relationship to the ribonuclease activity were not clear. Here, we show that helicase activity is dependent on ATP and have identified ATP-binding Walker A and Walker B motifs that are present in Escherichia coli RNase R and in 88% of mesophilic bacterial genera analyzed, but absent from thermophilic bacteria. We also show by mutational analysis that both of these motifs are required for helicase activity. Interestingly, the Walker A motif is located in the C-terminal region of RNase R, whereas the Walker B motif is in its N-terminal region implying that the two parts of the protein must come together to generate a functional ATP-binding site. Direct measurement of ATP binding confirmed that ATP binds only when double-stranded RNA is present. Detailed analysis of the helicase activity revealed that ATP hydrolysis is not required because both adenosine 5'-O-(thiotriphosphate) and adenosine 5'-(ß,γ-imino)triphosphate can stimulate helicase activity, as can other nucleoside triphosphates. Although the nuclease activity of RNase R is not needed for its helicase activity, the helicase activity is important for effective nuclease activity against a dsRNA substrate, particularly at lower temperatures and with more stable duplexes. Moreover, competition experiments and mutational analysis revealed that the helicase activity utilizes the same catalytic channel as the nuclease activity. These findings indicate that the helicase activity plays an essential role in the catalytic efficiency of RNase R.

Human DNA Exonuclease TREX1 Is Also an Exoribonuclease That Acts on Single-stranded RNA.

3' repair exonuclease 1 (TREX1) is a known DNA exonuclease involved in autoimmune disorders and the antiviral response. In this work, we show that TREX1 is also a RNA exonuclease. Purified TREX1 displays robust exoribonuclease activity that degrades single-stranded, but not double-stranded, RNA. TREX1-D200N, an Aicardi-Goutieres syndrome disease-causing mutant, is defective in degrading RNA. TREX1 activity is strongly inhibited by a stretch of pyrimidine residues as is a bacterial homolog, RNase T. Kinetic measurements indicate that the apparent Km of TREX1 for RNA is higher than that for DNA. Like RNase T, human TREX1 is active in degrading native tRNA substrates. Previously reported TREX1 crystal structures have revealed that the substrate binding sites are open enough to accommodate the extra hydroxyl group in RNA, further supporting our conclusion that TREX1 acts on RNA. These findings indicate that its RNase activity needs to be taken into account when evaluating the physiological role of TREX1.

How a CCA sequence protects mature tRNAs and tRNA precursors from action of the processing enzyme RNase BN/RNase Z.

In many organisms, 3' maturation of tRNAs is catalyzed by the endoribonuclease, RNase BN/RNase Z, which cleaves after the discriminator nucleotide to generate a substrate for addition of the universal CCA sequence. However, tRNAs or tRNA precursors that already contain a CCA sequence are not cleaved, thereby avoiding a futile cycle of removal and readdition of these essential residues. We show here that the adjacent C residues of the CCA sequence and an Arg residue within a highly conserved sequence motif in the channel leading to the RNase catalytic site are both required for the protective effect of the CCA sequence. When both of these determinants are present, CCA-containing RNAs in the channel are unable to move into the catalytic site; however, substitution of either of the C residues by A or U or mutation of Arg(274) to Ala allows RNA movement and catalysis to proceed. These data define a novel mechanism for how tRNAs are protected against the promiscuous action of a processing enzyme.

Prospective evaluation of (68)Ga-DOTANOC PET-CT in differentiated thyroid cancer patients with raised thyroglobulin and negative (131)I-whole body scan: comparison with (18)F-FDG PET-CT.

PURPOSE: The purpose of the study was to evaluate the role of (68)Ga-DOTANOC PET-CT in differentiated thyroid cancer (DTC) patients with negative (131)I-whole body scan (WBS) along with serially increasing serum thyroglobulin (Tg), and compare the same with (18)F-FDG PET-CT. METHODS: Sixty two DTC patients with serially rising Tg levels and negative (131)I-WBS were prospectively enrolled. All patients underwent (68)Ga-DOTANOC PET-CT and (18)F-FDG PET-CT within an interval of two weeks. PET-CT analysis was done on a per-patient basis, location wise and lesion wise. All PET-CT lesions were divided into four categories-local, nodal, pulmonary and skeletal. Histopathology and/or serial serum Tg level, clinical and imaging follow up (minimum-1 year) were used as a reference standard. RESULTS: Ga-DOTANOC PET-CT demonstrated disease in 40/62 (65 %) patients and (18)F-FDG PET-CT in 45/62 (72 %) patients, with no significant difference on McNemar analysis (p = 0.226). Per-patient sensitivity and specificity of (68)Ga-DOTANOC PET-CT was 78.4 %, 100 %, and for (18)F-FDG PET-CT was 86.3 %, 90.9 %, respectively. Out of 186 lesions detected by both PET-CTs, 121/186 (65 %) lesions were seen on (68)Ga-DOTANOC PET-CT and 168/186 (90.3 %) lesions on (18)F-FDG PET-CT (p < 0.0001). There were 103/186 (55 %) lesions concordant on both. Excellent agreement was noted between (68)Ga-DOTANOC PET-CT and (18)F-FDG PET-CT for detection of local disease (ĸ = 0.92), while moderate agreement was noted for nodal and pulmonary disease (ĸ = 0.67). (68)Ga-DOTANOC PET-CT changed management in 21/62 (34 %) patients and (18)F-FDG PET-CT in 17/62 (27 %) patients. CONCLUSION: Ga-DOTANOC PET-CT is inferior to (18)F-FDG PET-CT on lesion based but not on patient based analysis for detection of recurrent/residual disease in DTC patients with negative WBS scan and elevated serum Tg levels. It can also help in selection of potential candidates for peptide receptor radionuclide therapy.

Diagnostic accuracy of (68)Ga-DOTANOC PET/CT imaging in pheochromocytoma.

PURPOSE: The purpose of the present study was to evaluate the diagnostic accuracy of (68)Ga-DOTANOC positron emission tomography (PET)/CT in patients with suspicion of pheochromocytoma. METHODS: Data of 62 patients [age 34.3 ± 16.1 years, 14 with multiple endocrine neoplasia type 2 (MEN2)] with clinical/biochemical suspicion of pheochromocytoma and suspicious adrenal lesion on contrast CT (n = 70), who had undergone (68)Ga-DOTANOC PET/CT, were retrospectively analyzed. PET/CT images were analyzed visually as well as semiquantitatively, with measurement of maximum standardized uptake value (SUVmax), SUVmean, SUVmax/SUVliver, and SUVmean/SUVliver. Results of PET/CT were compared with (131)I-metaiodobenzylguanidine (MIBG) imaging, which was available in 40 patients (45 lesions). Histopathology and/or imaging/clinical/biochemical follow-up (minimum 6 months) was used as reference standard. RESULTS: The sensitivity, specificity, and accuracy of (68)Ga-DOTANOC PET/CT was 90.4, 85, and 88.7%, respectively, on patient-based analysis and 92, 85, and 90%, respectively, on lesion-based analysis. (68)Ga-DOTANOC PET/CT showed 100% accuracy in patients with MEN2 syndrome and malignant pheochromocytoma. On direct comparison, lesion-based accuracy of (68)Ga-DOTANOC PET/CT for pheochromocytoma was significantly higher than (131)I-MIBG imaging (91.1 vs 66.6%, p = 0.035). SUVmax was higher for pheochromocytomas than other adrenal lesions (p = 0.005), MEN2-associated vs sporadic pheochromocytoma (p = 0.012), but no difference was seen between benign vs malignant pheochromocytoma (p = 0.269). CONCLUSION: (68)Ga-DOTANOC PET/CT shows high diagnostic accuracy in patients with suspicion of pheochromocytoma and is superior to (131)I-MIBG imaging for this purpose. Best results of (68)Ga-DOTANOC PET/CT are seen in patients with MEN2-associated and malignant pheochromocytoma.

Diagnostic accuracy of ¹8F-FDG PET/CT for detection of suspected recurrence in patients with oesophageal carcinoma.

PURPOSE: To evaluate the role of (18)F-FDG PET/CT in the detection of recurrence in patients with oesophageal carcinoma, suspected clinically or following conventional investigations. METHODS: This was a retrospective study. Data from 180 patients (age 56.3 ± 10.4 years; 126 men, 54 women) with histopathologically proven oesophageal carcinoma (squamous cell 115, adenocarcinoma 59, neuroendocrine carcinoma 4, small cell 1, poorly differentiated 1) who had undergone 227 (18)F-FDG PET/CT studies for suspected recurrence were analysed. Recurrence was suspected clinically or following conventional investigations. PET/CT images were revaluated by two nuclear medicine physicians in consensus. Findings were grouped into local, nodal and distant recurrence. Results were compared to those from contrast-enhanced (CE) CT when available (109 patients). Clinical/imaging follow-up (minimum 6 months) with histopathology (when available) was taken as the reference standard. RESULTS: Of the 227 (18)F-FDG PET/CT studies,166 were positive and 61 were negative for recurrent disease. PET/CT showed local recurrence in 134, nodal recurrence in 115 and distant recurrence in 47, with more than one site of recurrence in 34. The PET/CT findings were true-positive in 153 studies, true-negative in 54, false-positive in 13 and false-negative in 7. The sensitivity of (18)F-FDG PET/CT was 96%, the specificity was 81%, the positive and negative predictive values were 92% and 89%, respectively, and the accuracy was 91%. PET/CT showed similar accuracy in patients with squamous cell carcinoma and in those with adenocarcinoma (P = 0.181).(18)F-FDG PET/CT was more specific than CECT (67% vs. 21%; P < 0.0001). PET/CT was superior to CECT for the detection of nodal recurrence (P < 0.0001), but not local recurrence (P = 0.093) or distant metastases (P = 0.441). CONCLUSION: (18)F-FDG PET/CT shows high accuracy in the detection of suspected recurrence in patients with oesophageal carcinoma. It is more specific than and is superior to CECT in the detection of nodal recurrence.

An approach for conjugation of (177) Lu- DOTA-SCN- Rituximab (BioSim) & its evaluation for radioimmunotherapy of relapsed & refractory B-cell non Hodgkins lymphoma patients.

BACKGROUND & OBJECTIVES: The prerequisite of radioimmunotherapy is stable binding of a radionuclide to monoclonal antibodies, which are specific to the tumour-associated antigen. Most B-cell lymphomas express CD20 antigen on the surface of the tumour cells, making it a suitable target for therapeutic radioactive monoclonal antibodies. In the present study, the immunoconjugate of biosimilar Rituximab (Reditux™) and macrocyclic chelator, p-SCN-Bz-DOTA, was prepared and radiolabelled with Lutetium-177 followed by quality control procedures. METHODS: Rituximab(BioSim) was desalted with sodium bicarbonate (0.1M, pH 9.0) and incubated with DOTA-SCN (1:50). The effectiveness of the conjugation was evaluated by determining the number of chelators per antibody molecule. This conjugate was radiolabelled with Lutetium-177 and purified using PD10 column. The quality control parameters like pH, clarity, radiochemical purity, in vitro stability and sterility were studied. Immunoreactivity of 177 Lu-DOTA-Rituximab (BioSim) was assessed using RAMOS cells. The radioimmunoconjugate (RIC) after stringent quality assurance was injected in three patients and the biodistribution profile was analysed. RESULTS: An average of 4.25 ± 1.04 p-SCN-Bz-DOTA molecules could be randomly conjugated to a single molecule of Rituximab (BioSim).The radiochemical purity of the labelled antibody was > 95 per cent with preserved affinity for CD20 antigen. The final preparation was stable up to about 120 h when tested under different conditions. A favourable biodistribution profile was observed with liver showing the maximum uptake of the RIC. INTERPRETATION & CONCLUSIONS: A favourable radiochemical purity, stability and biodistribution of the radiolabelled immunoconjugate indicate that clinical trials for evaluation of toxicity and efficacy of 177 Lu-DOTA-antiCD20 antibody-Rituximab (BioSim) in patients of relapsed and refractory non Hodgkin's lymphoma can be considered.

Exoribonuclease and endoribonuclease activities of RNase BN/RNase Z both function in vivo.

Escherichia coli RNase BN, a member of the RNase Z family of endoribonucleases, differs from other family members in that it also can act as an exoribonuclease in vitro. Here, we examine whether this activity of RNase BN also functions in vivo. Comparison of the x-ray structure of RNase BN with that of Bacillus subtilis RNase Z, which lacks exoribonuclease activity, revealed that RNase BN has a narrower and more rigid channel downstream of the catalytic site. We hypothesized that this difference in the putative RNA exit channel might be responsible for the acquisition of exoribonuclease activity by RNase BN. Accordingly, we generated several mutant RNase BN proteins in which residues within a loop in this channel were converted to the corresponding residues present in B. subtilis RNase Z, thus widening the channel and increasing its flexibility. The resulting mutant RNase BN proteins had reduced or were essentially devoid of exoribonuclease activity in vitro. Substitution of one mutant rbn gene (P142G) for wild type rbn in the E. coli chromosome revealed that the exoribonuclease activity of RNase BN is not required for maturation of phage T4 tRNA precursors, a known specific function of this RNase. On the other hand, removal of the exoribonuclease activity of RNase BN in a cell lacking other processing RNases leads to slower growth and affects maturation of multiple tRNA precursors. These findings help explain how RNase BN can act as both an exo- and an endoribonuclease and also demonstrate that its exoribonuclease activity is capable of functioning in vivo, thus widening the potential role of this enzyme in E. coli.

18F-FDOPA PET/CT for detection of recurrence in patients with glioma: prospective comparison with 18F-FDG PET/CT.

PURPOSE: Differentiation between recurrence and radiation necrosis in patients with glioma is crucial, since the two entities have completely different management and prognosis. The purpose of the present study was to compare the efficacies of (18)F-FDG PET/CT and 3,4-dihydroxy-6-[(18)F]fluoro-phenylalanine ((18)F-FDOPA) PET/CT in detection of recurrent gliomas. METHODS: A total of 28 patients (age 38.82 ± 1.25 years; 85.7% men) with histopathologically proven glioma with clinical/imaging suspicion of recurrence were evaluated using (18)F-FDG PET/CT and (18)F-FDOPA PET/CT. (18)F-FDG PET/CT and (18)F-FDOPA PET/CT images were evaluated qualitatively and semiquantitatively. The combination of clinical follow-up, repeat imaging and/or biopsy (when available) was taken as the reference standard. RESULTS: Based on the reference standard, 21 patients were positive and 7 were negative for tumour recurrence. The sensitivity, specificity and accuracy of (18)F-FDG PET/CT were 47.6%, 100% and 60.7%, respectively, and those of (18)F-FDOPA PET/CT were 100%, 85.7% and 96.4%, respectively. The results of (18)F-FDG PET/CT and (18)F-FDOPA PET/CT were concordant in 57.1% of patients (16 of 28) and discordant in 42.9% (12 of 28). The difference in the findings between (18)F-FDG PET/CT and (18)F-FDOPA PET/CT was significant (P = 0.0005, McNemar's test). The difference was significant for low-grade tumours (P = 0.0039) but not for high-grade tumours (P = 0.250). CONCLUSION: (18)F-FDOPA PET/CT is highly sensitive and specific for detection of recurrence in glioma patients. It is superior to (18)F-FDG PET/CT for this purpose and is especially advantageous in patients with low-grade gliomas.

Diagnostic accuracy of 18F-FDG PET/CT for detecting recurrence in patients with primary skeletal Ewing sarcoma.

PURPOSE: To evaluate the diagnostic accuracy of (18)F-FDG PET/CT for detecting recurrence in patients with primary skeletal Ewing sarcoma. METHODS: We retrospectively analysed data from 53 patients (age 20.1 ± 10.5 years, 39 male) who had undergone 71 (18)F-FDG PET/CT studies for suspected recurrence (52 studies) or for routine follow-up (19 studies) after primary therapy of skeletal Ewing sarcoma. (18)F-FDG PET/CT studies were evaluated qualitatively and quantitatively (maximum standardized uptake value, SUVmax) by two nuclear medicine physicians in consensus. Sensitivity, specificity, predictive values and accuracy were calculated on per study basis. Clinical/imaging follow-up (minimum 6 months) and/or histopathology (when available) were taken as the reference standard. RESULTS: Of the total of 71 (18)F-FDG PET/CT studies, 42 (59.1%) were positive for recurrence and 29 (40.9%) were negative for recurrence. Local recurrence was most common (38 studies) followed by bone metastasis (9 studies), and node and lung metastasis (2 studies each). Of the 71 studies, 38 were true-positive, 27 were true-negative, 4 were false-positive and 2 were false-negative. Overall per study based sensitivity was 95%, specificity was 87%, PPV was 90%, NPV was 93% and accuracy was 91.5%. No significant difference was found in the accuracy of PET/CT between the suspected recurrence group and the routine follow-up group (94% vs. 84%; P = 0.390). Overall mean lesion SUVmax was 7.8 ± 4.1 (range 1.9-17.2). No site-based difference was found in SUVmax. CONCLUSION: (18)F-FDG PET/CT demonstrates high diagnostic accuracy for detecting recurrence in patients with primary skeletal Ewing sarcoma, when it is suspected (clinically or on imaging) or during routine follow-up.

Comparative diagnostic accuracy of contrast-enhanced MRI and (18)F-FDOPA PET-CT in recurrent glioma.

OBJECTIVES: To compare the diagnostic accuracy of contrast enhanced magnetic resonance imaging (Ce-MRI) and (18)F-fluorodopa ((18)F-FDOPA) positron emission tomography (PET)-computed tomography (CT) for detecting recurrent glioma. METHODS: In this prospective study, 35 patients (age, 36.62 ± 0.86 years; 80 % male) with histopathologically proven glioma with clinical suspicion of recurrence were evaluated using Ce-MRI and (18)F-FDOPA PET-CT. (18)F-FDOPA PET-CT images were evaluated qualitatively and semi-quantitatively. Combination of clinical follow-up (minimum 1 year), repeat imaging and/or biopsy (when available) was taken as the reference standard. RESULTS: Based on the reference standard, 26 patients were positive and nine were negative for recurrence. The sensitivity, specificity and accuracy of Ce-MRI were 92.3 %, 44.4 % and 80 % respectively, whereas those of (18)F-FDOPA PET-CT were 100 %, 88.89 % and 97.1 % respectively. Results of Ce-MRI and (18)F-FDOPA PET-CT were concordant in 74.3 % (29/35) and discordant in 17.1 % of patients (6/35). On McNemar analysis the difference was not statistically significant overall (P = 0.687), for high-grade tumour (P = 0.5) or low-grade tumours (P = 1.0). However, (18)F-FDOPA PET-CT was more specific than Ce-MRI overall (P = 0.0002), for high-grade tumour (P = 0.006) and low-grade tumours (P = 0.004). CONCLUSION: F-FDOPA PET-CT shows a high but comparable diagnostic accuracy to Ce-MRI for the detection of recurrent glioma. However, it is more specific than Ce-MRI. KEY POINTS: • Recurrent glioma in the postoperative site remains a diagnostic dilemma. • (18) F-FDOPA PET-CT shows high diagnostic accuracy for detecting recurrent glioma. • Diagnostic accuracies for (18) F-FDOPA PET-CT and contrast enhanced MRI are comparable. • However, (18) F-FDOPA PET-CT is more specific than Ce-MRI for recurrent glioma.

Quantitative assessment of cardiac mechanical synchrony using equilibrium radionuclide angiography.

BACKGROUND: Data on normal parameters of cardiac mechanical synchrony is limited, variable and obtained from small cohorts till date. In most studies, software used for such assessment has not been mentioned. The aim of study is to establish normal values of mechanical synchrony with equilibrium radionuclide angiography (ERNA) in a larger population using commercially available software. METHODS: We retrospectively analysed ERNA studies of 108 patients having low pretest likelihood of coronary artery disease, no known history of cardiac disease, normal electrocardiogram and whose ERNA studies were considered normal by experienced observers. In addition, ten patients diagnosed with dilated cardiomyopathy (DCM) and having LVEF ≤ 40% underwent ERNA. Fourier first harmonic analysis of phase images was used to quantify synchrony parameters using commercially available software (XT-ERNA). Intraventricular synchrony for each ventricle was measured as the standard deviation of the LV and RV mean phase angles (SD LVmPA and SD RVmPA, respectively). Interventricular synchrony was measured as LV-RVmPA. Absolute interventricular delay was calculated as absolute difference between LV and RVmPA (without considering ± sign). All variables were expressed in milliseconds (ms) and degree (°). Intra-observer and inter-observer variabilities were assessed. Cut-off values for parameters were calculated from the normal database, and validated against patient group. RESULTS: On phase analysis, LVmPA was observed to be 343 ± 48.5 milliseconds (174.7° ± 18.5°), SD LVmPA was 16.3 ± 5.4 milliseconds (8.2° ± 2.5°), RVmPA was 339 ± 50.4 milliseconds (171.8° ± 18.5°) and SD RVmPA was 37.3 ± 15.7 milliseconds (18.7° ± 7.2°). LV-RVmPA was observed to be 3.9 ± 21.7 milliseconds (2.9° ± 9.6°) and absolute interventricular delay was 16.3 ± 14.8 milliseconds (7.9° ± 6.1°). The cut-off values for the presence of dyssynchrony were estimated as SD LVmPA > 27.1 milliseconds (>13.2°), SD RVmPA > 68.7 milliseconds (>33.1°) and LV-RVmPA > 47.3 milliseconds (>22.1°). There was no statistically significant intra-observer or inter-observer variability. Using these cut offs, 9 patients with DCM showed the presence of left intraventricular dyssynchrony, 5 had right intraventricular dyssynchrony and 2 had interventricular dyssynchrony. CONCLUSIONS: ERNA phase analysis offers an objective and reproducible tool to quantify cardiac mechanical synchrony using commercially available software and can be used in routine clinical practice to assess mechanical dyssynchrony.

Somatostatin receptor-based PET/CT of intracranial tumors: a potential area of application for 68 Ga-DOTA peptides?

OBJECTIVE: Similar to neuroendocrine tumors (NETs) at other sites, a wide array of intracranial tumors also express somatostatin receptors (SSTRs). This expression can be exploited for both imaging and therapy. The introduction of (68)Ga-labeled tetraazacyclododecanetetraacetic acid (DOTA)-peptide PET/CT has given new dimension to SSTR-based imaging because of its improved sensitivity and excellent spatial resolution. CONCLUSION: However, in contrast to gastropancreatic and bronchopulmonary NETs, limited literature is available regarding the use of (68)Ga-DOTA-peptide PET/CT in intracranial tumors. Here, we briefly review the available literature and highlight the potential role that (68)Ga-DOTA-peptide PET/CT can play in the management of intracranial tumors.

Diagnostic performance of somatostatin receptor PET/CT using 68Ga-DOTANOC in gastrinoma patients with negative or equivocal CT findings.

PURPOSE: Contrast-enhanced CT (CECT) is a standard investigative procedure in the localization of gastrinomas. Small tumors are often missed and metastatic lesions may remain occult on CT. The purpose of present study was to prospectively evaluate the diagnostic performance of (68)Ga-labeled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-1-NaI(3)-Octreotide ((68)Ga-DOTANOC) positron emission tomography/computed tomography (PET/CT) in gastrinoma patients with negative or equivocal CT findings. METHODS: Twenty-five patients (age 46.6 ± 13.3 years; male 60%) with clinical/biochemical diagnosis of gastrinoma and negative or equivocal findings on CECT were prospectively evaluated. All of them underwent (68)Ga-DOTANOC PET/CT which was evaluated by two nuclear medicine physicians in consensus. Combination of histopathology, serum gastrin, endoscopy, and follow-up imaging were taken as reference standard. RESULTS: (68)Ga-DOTANOC PET/CT was positive in 17 patients and negative in 8 patients, yielding an overall detection rate of 68%. It was positive 13/20 patients who underwent baseline evaluation and in 4/5 post-treatment patients. Of the 11 patients who had a negative CT result, (68)Ga-DOTANOC PET/CT was positive in four cases (detection rate 36.4%), while it was abnormal in 13/14 patients who had equivocal CT findings (detection rate 92.8%). Diagnostic performance of (68)Ga-DOTANOC PET/CT was superior in patients with equivocal CECT findings than that in patients with negative CECT (P = 0.010). CONCLUSION: (68)Ga-DOTANOC PET/CT appears to be useful in patients with gastrinoma with negative or equivocal results on CECT, especially the latter group.