Development and establishment of a parallel plate ionization chamber as a transfer standard for measurement of dose to tissue in beta radiation fields

A parallel-plate ionization chamber (PPC) with a nominal volume of 8.16 cm³ was developed based on theoretically simulated design parameters. Its purpose is to serve as a transfer standard for dosimetry in a beta radiation field. The entrance window of the PPC consists of an aluminized Mylar sheet with a thickness of 1.4 mg/cm2. The collecting and guard electrodes are created by applying a graphite coating on a Poly Methyl Methacrylate (PMMA) substrate with a thickness of 5 mm. The nominal sheet resistance of the graphite-coated PMMA substrate was measured using a four-probe technique and found to be approximately 800 Ω per square (Ω/□). Dosimetric characterization of the PPC was performed in the ISO 6980 reference beta radiation field, utilizing 90Sr-90Y and 85Kr beta radiation sources. The assessment included studies on short-term stability, linearity, current-to-voltage characteristics, stabilization time, and leakage current. The PPC was calibrated and established as a transfer standard using the 'Extrapolation Ionization Chamber,' recognized as an absolute standard for dose to tissue in 90Sr-90Y and 85Kr beta sources within the laboratory. The calibration coefficient of the PPC indicates an energy dependence of 0.6 % for 90Sr-90Y and 85Kr beta sources.

Abstract P3-03-40: A prospective two arm comparative study of indo-cyanine green (ICG) enhanced fluorescence imaging vs conventional methods (blue dye and radiocolloid/hand held gamma probe) for sentinel lymph node detection in breast cancer - Going beyond the horizon

Background:

The dual technique with radio colloid and blue dye is the gold standard in sentinel lymph node biopsy (SLNB) to stage axilla in breast cancer. However due to cost & infrastructural demands of nuclear medicine department most of the oncology centers are not doing slnb or are doing SLNB with blue dye which is not a standard of care. Indocyanine green (ICG) has recently been used as a method of identifying sentinel lymph nodes. Studies have shown that ICG fluorescence imaging alone or in combination with the blue dye method or the radionuclide method is a safe and easy technique. The objective of the present study was to assess the diagnostic performance of sentinel lymph node (SLN) biopsy using the indocyanine green (ICG) fluorescence method compared with that using the conventional method in detection of sentinel lymph nodes.

Material & Methods:

60 patients diagnosed with early breast cancer underwent the SLNB procedure using technetium-99m radio colloid (R), methylene blue dye (MB), and ICG. Fluorescence imaging was done using an indigenously designed , very economical fluorescence imaging system, Irilic.nm fluorescence imaging along with Indocyanine green. All SLNs that were removed during surgery were labelled as hot, blue or/and fluorescent and sent for pathological examination. The detection rate of SLNs and positive SLNs, and the number of SLNs of ICG, MB+ R, ICG + MB, ICG + R were compared. Injection safety of ICG and MB was evaluated.

Results:

Sentinel Lymph Node was identified in all 60 cases. Total Sentinel lymph nodes removed was 145 (Mean=2, Range 2-5), ICG was able to identify more nodes than the dual dye technique. The identification rate with the dual dye technique was 95%, with blue dye alone 93.6% and with radioisotope alone 96.8% whereas with ICG alone was 100%, with ICG + MB was 96.6% & ICG + R was 96.6 %. 28(46.6%) out of 60 patients had positive nodes which was identified by both dual dye & ICG. None of the patients had any local or systemic reaction with ICG, 3 patients with blue dye had tattooing & staining of skin.

Conclusion:

ICG is as effective as the dual dye for SLNB. ICG is safe & reliable. In addition, as a near-infrared dye, it has the advantages of real-time visualization, lower cost, and wider availability. It can be a boon for developing countries & second tier referral centers of developed country where there is limited access to nuclear medicine department & radiocolloid and even if its accesible the cost involved is too high which comes with added radiation exposure to medical personnel handling them. A combination of blue dye and ICG is useful dual approach when radioisotope is unavailable.

ICG verus Conventional Dye Clinical Profile ICGRadio-colloid+ B;ue DyeDetection Rate100%95%Sensitivity100% (CI 83.16% to 100.00%)100% (CI 83.16% to 100.00%)Positive Predictive Value100%100%Accuracy100%100%

Citation Format: Somashekhar S, Rohit Kumar C, Zaveri S, Rajgopal A, Rakshit S, Ali SH. A prospective two arm comparative study of indo-cyanine green (ICG) enhanced fluorescence imaging vs conventional methods (blue dye and radiocolloid/hand held gamma probe) for sentinel lymph node detection in breast cancer - Going beyond the horizon [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-03-40.

Tailored Polyproteins Using Sequential Staple and Cut

Polyproteins, individual protein units joined covalently in tandem, have evolved as a promising tool for measuring the dynamic folding of biomacromolecules in single-molecule force spectroscopy. However, the synthetic routes to prepare polyproteins have been a bottleneck, and urge development of in vitro methods to knit individual protein units covalently into polyprotein. Employing two enzymes of orthogonal functionalities periodically in sequence, we synthesized monodispersed polyproteins on a solid surface. We used Sortase A (SrtA), the enzyme known for sequence specific transpeptidation, to staple protein units covalently through peptide bonds. Exploiting the sequence-specific peptide cleaving ability of TEV protease, we controlled the progress of the reaction to one attachment at a time. Finally, with unique design of the unit proteins we control the orientation of proteins in polyprotein. This simple conjugation has the potential to staple proteins with different functionalities and from different expression systems, in any number in the polyprotein and, above all, via irreversible peptide bonds. Multiple chimeric constructs can also be synthesized with interchangeable protein units.

HIV-TB co-infection: mechanisms that drive reactivation of Mycobacterium tuberculosis in HIV infection

HIV infection predisposes the host to tuberculosis by impairing the hosts' immune system principally by killing and altering CD4 T-cell function. How HIV infection disrupts CD4 T-cell function, which specifically compromises host immunity to Mycobacterium tuberculosis, is poorly understood and is a critical roadblock in developing better vaccine- or immune-based strategies to control and monitor TB in HIV-infected subjects. This review considers key pathways that are altered in HIV-infected subjects that impair anti-TB immunity.

Association of AFLP and SSR markers with agronomic and fibre quality traits in Gossypium hirsutum L

Molecular markers linked to QTL contributing to agronomic and fibre quality traits would be useful for cotton improvement. We have attempted to tag yield and fibre quality traits with AFLP and SSR markers using F(2) and F(3) populations of a cross between two Gossypium hirsutum varieties, PS56-4 and RS2013. Out of 50 AFLP primer combinations and 177 SSR primer pairs tested, 32 AFLP and four SSR primers were chosen for genotyping F(2) individuals. Marker-trait associations were studied for eight agronomic and five fibre quality traits through simple and multiple regression analysis (MRA) using a set of 92 AFLP polymorphic loci and four SSR markers. Simple linear regression analysis (SLRA) identified 23 markers for eight different traits whereas multiple regression analysis identified 30 markers for at least one of the 13 traits. SSR marker BNL 3502 was consistently identified to be associated with fibre strength. While all the markers identified in SLRA were also detected in MRA, as many as 16 of the 30 markers were identified to be associated with respective traits in both F2 and F3 generations. The markers explained up to 41 per cent of phenotypic variation for individual traits. A number of markers were found to be associated with multiple traits suggesting clustering of QTLs for fibre quality traits in cotton.

Reduction of copper(II) by iron(II)

Laboratory and field investigations have clearly demonstrated the important role of reduced iron (Fe(II)) in reductive transformations of first-row transition metal species. However, interactions of Fe(II) and copper (Cu) are not clearly understood. This study examined the reduction of Cu(II) by Fe(II) in stirred-batch experiments at pH 5.2 and 5.5 as influenced by chloride (Cl-) concentration (0.002-0.1 M), initial metal concentration (0.1-9.1 mM), and reaction time (1-60 min) under anoxic conditions. Reduction of Cu(II) to Cu(I) by dissolved Fe(II) was rapid under all experimental conditions and the stability of the products explains the driving force for the redox reaction. Under conditions of low [Cl-] and high initial metal concentration, >40% of total Cu and Fe were removed from solution after 1 min, which accompanied formation of a brownish-red precipitate. X-ray diffraction (XRD) patterns of the precipitates revealed the presence of cuprite (Cu2O), a Cu(I) mineral, based on d-spacings located at 0.248, 0.215, 0.151, and 0.129 nm. Fourier transform infrared (FTIR) spectroscopy corroborated XRD data for the presence of Cu2O, with features located at 518, 625, and 698 cm(-1). Increasing [Cl-] stabilized the dissolved Cu(I) product against Cu2O precipitation and resulted in more Fe precipitated from solution (relative to Cu) that appears to be present as poorly crystalline lepidocrocite (gamma-FeOOH). This process may be important in anoxic soil environments, where dissolved Fe(II) levels can accumulate.

Camptothecin induced mitochondrial dysfunction leading to programmed cell death in unicellular hemoflagellate Leishmania donovani

The parasites of the order kinetoplastidae including Leishmania spp. emerge from most ancient phylogenic branches of unicellular eukaryotic lineages. In their life cycle, topoisomerase I plays a significant role in carrying out vital cellular processes. Camptothecin (CPT), an inhibitor of DNA topoisomerase I, induces programmed cell death (PCD) both in the amastigotes and promastigotes form of L. donovani parasites. CPT-induced cellular dysfunction in L. donovani promastigotes is characterized by several cytoplasmic and nuclear features of apoptosis. CPT inhibits cellular respiration that results in mitochondrial hyperpolarization taking place by oligomycin-sensitive F0-F1 ATPase-like protein in leishmanial cells. During the early phase of activation, there is an increase in reactive oxygen species (ROS) inside cells, which causes subsequent elevation in the level of lipid peroxidation and decrease in reducing equivalents like GSH. Endogenous ROS formation and lipid peroxidation cause eventual loss of mitochondrial membrane potential. Furthermore, cytochrome c is released into the cytosol in a manner independent of involvement of CED3/CPP32 group of proteases and unlike mammalian cells it is insensitive to cyclosporin A. These events are followed by activation of both CED3/CPP32 and ICE group of proteases in PCD of Leishmania. Taken together, our study indicates that different biochemical events leading to apoptosis in leishmanial cells provide information that could be exploited to develop newer potential therapeutic targets.

Computation of optical flow using basis functions

The issues governing the computation of optical flow in image sequences are addressed. The trade-off between accuracy versus computation cost is shown to be dependent on the redundancy of the image representation. This dependency is highlighted by reformulating Horn's (1986) algorithm, making explicit use of the approximations to the continuous basis functions underlying the discrete representation. The computation cost of estimating optical flow, for a fixed error tolerance, is shown to be a minimum for images resampled at twice the Nyquist rate. The issues of derivative calculation and multiresolution representation are also briefly discussed in terms of basis functions and information encoding. A multiresolution basis function formulation of Horn's algorithm is shown to lead to large improvements in dealing with high frequencies and large displacements.

Neural responses to polar, hyperbolic, and Cartesian gratings in area V4 of the macaque monkey

1. We studied the responses of 103 neurons in visual area V4 of anesthetized macaque monkeys to two novel classes of visual stimuli, polar and hyperbolic sinusoidal gratings. We suspected on both theoretical and experimental grounds that these stimuli would be useful for characterizing cells involved in intermediate stages of form analysis. Responses were compared with those obtained with conventional Cartesian sinusoidal gratings. Five independent, quantitative analyses of neural responses were carried out on the entire population of cells. 2. For each cell, responses to the most effective Cartesian, polar, and hyperbolic grating were compared directly. In 18 of 103 cells, the peak response evoked by one stimulus class was significantly different from the peak response evoked by the remaining two classes. Of the remaining 85 cells, 74 had response peaks for the three stimulus classes that were all within a factor of 2 of one another. 3. An information-theoretic analysis of the trial-by-trial responses to each stimulus showed that all but two cells transmitted significant information about the stimulus set as a whole. Comparison of the information transmitted about each stimulus class showed that 23 of 103 cells transmitted a significantly different amount of information about one class than about the remaining two classes. Of the remaining 80 cells, 55 had information transmission rates for the three stimulus classes that were all within a factor of 2 of one another. 4. To identify cells that had orderly tuning profiles in the various stimulus spaces, responses to each stimulus class were fit with a simple Gaussian model. Tuning curves were successfully fit to the data from at least one stimulus class in 98 of 103 cells, and such fits were obtained for at least two classes in 87 cells. Individual neurons showed a wide range of tuning profiles, with response peaks scattered throughout the various stimulus spaces; there were no major differences in the distributions of the widths or positions of tuning curves obtained for the different stimulus classes. 5. Neurons were classified according to their response profiles across the stimulus set with two objective methods, hierarchical cluster analysis and multidimensional scaling. These two analyses produced qualitatively similar results. The most distinct group of cells was highly selective for hyperbolic gratings. The majority of cells fell into one of two groups that were selective for polar gratings: one selective for radial gratings and one selective for concentric or spiral gratings. There was no group whose primary selectivity was for Cartesian gratings. 6. To determine whether cells belonging to identified classes were anatomically clustered, we compared the distribution of classified cells across electrode penetrations with the distribution that would be expected if the cells were distributed randomly. Cells with similar response profiles were often anatomically clustered. 7. A position test was used to determine whether response profiles were sensitive to precise stimulus placement. A subset of Cartesian and non-Cartesian gratings was presented at several positions in and near the receptive field. The test was run on 13 cells from the present study and 28 cells from an earlier study. All cells showed a significant degree of invariance in their selectivity across changes in stimulus position of up to 0.5 classical receptive field diameters. 8. A length and width test was used to determine whether cells preferring non-Cartesian gratings were selective for Cartesian grating length or width. Responses to Cartesian gratings shorter or narrower than the classical receptive field were compared with those obtained with full-field Cartesian and non-Cartesian gratings in 29 cells. Of the four cells that had shown significant preferences for non-Cartesian gratings in the main test, none showed tuning for Cartesian grating length or width that would account for their non-Cartesian res