Overexpression of flowering locus D (FLD) in Indian mustard (Brassica juncea) enhances tolerance to Alternaria brassicae and Sclerotinia sclerotiorum

KEY MESSAGE

Overexpression of BjFLD in Brassica juncea imparts resistance against fungal pathogens and increases the yield. These transgenics could lower the use of fungicides, which have detrimental effects on the environment. Productivity of Indian mustard (Brassica juncea) is adversely affected by fungal phytopathogens, Alternaria brassicae and Sclerotinia sclerotiorum. Arabidopsis flowering locus D (FLD) positively regulates jasmonic acid signaling and defense against necrotrophic pathogens. In this study, the endogenous FLD (B. juncea FLD; BjFLD) in Indian mustard was overexpressed in B. juncea to determine its role in biotic stress tolerance. We report the isolation, characterization, and functional validation of BjFLD. The transgene expression was confirmed by qRT-PCR. The constitutive overexpression of BjFLD enhanced the tolerance of B. juncea to A. brassicae and S. sclerotiorum, which was manifested as delayed appearance of symptom, impeded disease progression, and enhanced percentage of disease protection. The transgenic lines maintained a higher photosynthetic capacity and redox potential under biotic stress and could detoxify reactive oxygen species (ROS) by modulating the antioxidant machinery and physiochemical attributes. The BjFLD-overexpressing lines showed enhanced SA level as well higher NPR1 expression. The overexpression of BjFLD induced early flowering and higher seed yield in the transgenic lines. These findings indicate that overexpression of BjFLD enhances the tolerance of B. juncea to A. brassicae and S. sclerotiorum by induction of systemic acquired resistance and mitigating the damage caused by stress-induced ROS.

Histamine-release test in angioedema patients without urticaria - a retrospective cohort study of 404 patients

Summary

A subset of patients with angioedema (AE) and urticaria has histamine releasing autoantibodies. The histamine release test (HR-test) has been used as a tool in chronic urticaria to define the autoimmune subgroup and may possibly guide the clinician to a more personalized therapy, like omalizumab and cyclosporine. The prevalence and value of positive histamine releasing autoantibodies in monosymptomatic AE is sparsely described in the literature. The purpose of this study was to report the prevalence of positive histamine releasing autoantibodies in a cohort of patients with recurrent AE and evaluate the usefulness of this test in AE patients. We performed a retrospective cohort study of 612 patients referred due to AE between 1995 and 2013. HR-test results were available in 404 patients. In the sub-group of patients with AE and urticaria, 17.3% had a positive HR-test but only 4.3% of patients with mono-symptomatic AE had a positive HR-test. No statistically significant treatment benefits of antihistamines, corticosteroids or adrenaline were found comparing patients with angioedema +/- urticaria based on the result of the HR-test (negative / positive). Thus, the HR-test result cannot be used as predictor of the efficacy of anti-allergic treatment.

Characterization of key transcription factors as molecular signatures of HPV-positive and HPV-negative oral cancers

Prior studies established constitutively active AP-1, NF-κB, and STAT3 signaling in oral cancer. Differential expression/activation of specific members of these transcription factors has been documented in HPV-positive oral lesions that respond better to therapy. We performed a comprehensive analysis of differentially expressed, transcriptionally active members of these pivotal signaling mediators to develop specific signatures of HPV-positive and HPV-negative oral lesions by immunohistochemical method that is applicable in low-resource settings. We examined a total of 31 prospective and 30 formalin-fixed, paraffin-embedded tissues from treatment-naïve, histopathologically and clinically confirmed cases diagnosed as oral or oropharyngeal squamous cell carcinoma (OSCC/OPSCC). Following determination of their HPV status by GP5 + /GP6 +  PCR, the sequential sections of the tissues were evaluated for expression of JunB, JunD, c-Fos, p50, p65, STAT3, and pSTAT3(Y705), along with two key regulatory proteins pEGFR and p16 by IHC. Independent analysis of JunB and p65 showed direct correlation with HPV positivity, whereas STAT3 and pSTAT3 were inversely correlated. A combined analysis of transcription factors revealed a more restrictive combination, characterized by the presence of AP-1 and NF-κB lacking involvement of STAT3 that strongly correlated with HPV-positive tumors. Presence of STAT3/pSTAT3 with NF-κB irrespective of the presence or absence of AP-1 members was present in HPV-negative lesions. Expression of pSTAT3 strongly correlated with all the AP-1/NF-κB members (except JunD), its upstream activator pEGFRY1092 , and HPV infection-related negative regulator p16. Overall, we show a simple combination of AP-1, NF-κB, and STAT3 members' expression that may serve as molecular signature of HPV-positive lesions or more broadly the tumors that show better prognosis.

Levels of select organophosphates in human colostrum and mature milk samples in rural region of Faizabad district, Uttar Pradesh, India

Introduction: Human colostrum and mature milk samples from rural mothers were separately screened for organophosphate pesticides (OPPs). The samples were assessed for the pollution load they are transmitting to the nursing infant to determine potential toxicity. The role of colostrum for toxicity monitoring was assessed in comparison to mature milk as it is the very first infant food. Materials and methods: The pesticides were quantified using a Gas Chromatograph equipped with Electron Capture Detector (GC-ECD) and the results were further validated on GC linked with Mass Spectrophotometer (GC-MS) and Fourier transform infrared (FTIR). Results: A total of 33 samples were analyzed out of 40 samples collected. These samples were from 33 mothers. Out of these, 25 were colostrum samples and 8 were mature milk samples. Frequency percentage (N%) of organophosphates analyzed was highest for ethion (23.1% or 6/26) in colostrum and chlorpyrifos (50% or 4/8) in mature milk samples. Frequency percentage in colostrum was 19.2% (5/26) for chlorpyrifos and 3.8% (1/26) for dimethoate; 25.0% (2/8) mature milk samples carried dimethoate and 12.5% (1/8) carried ethion. Mean OPPs in colostrum: dimethoate (85.888 ng/g fat) > ethion (48.000 ng/g fat) > chlorpyrifos (4.003 ng/g fat); and mature milk: ethion (744.925 ng/g fat) > chlorpyrifos (37.274 ng/g fat) > dimethoate (26.752 ng/g fat). MS data revealed the presence of methyl parathion, which was not quantitated. None of the samples exceeded acceptable daily intake standards set by Joint Meeting on Pesticide Residues (JMPR). The study will pave way for further analysis on pesticide toxicology.

Modeling sulphur dioxide due to vehicular traffic using artificial neural network

The dispersion characteristics of vehicular exhaust are highly non-linear. The deterministic as well as numerical models are unable to predict these air pollutants precisely. Artificial neural network (ANN), having the capability to recognize the non-linearity present in the noisy data, has been used in the present work to model the emission concentration of sulphur dioxide from vehicular source in an urban area. ANN model is developed with different combinations of traffic and meteorological parameters. The model prediction reveals that the artificial neural network trained with both traffic and meteorological parameters together shows better performance in predicting SO2 concentration.

Vocal cord hemangioma

Laryngeal hemangiomas are relatively rare. Laryngeal hemangiomas occur in two main forms--infantile and adult laryngeal hemangiomas. While infantile hemangiomas are usually found to occur in the subglottis, adult hemangiomas occur commonly in the supraglottic regions of the larynx. Laryngeal hemangioma with cavernous features isolated to the free edge of the vocal fold is a very rare clinical finding. We present a case of hemangioma of the right vocal cord in an adult, which was managed successfully in our center.

Protein changes associated with ionizing radiation-induced apoptosis in human prostate epithelial tumor cells

Ionizing radiation (IR) is an important component in the therapy of localized prostate cancer. Identification of protein alterations during IR-induced apoptosis prostate cancer cells is an important step toward understanding the new metabolic status of the dying cell. In the present study, we report changes in protein profile that define the execution phase of the apoptotic response in the in vitro model of tumorigenic radiation-transformed SV40-immortalized human prostate epithelial cells (267B1-XR), induced to undergo programmed cell death by IR. We employed an approach that involves use of analytical two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) coupled with Western blotting with specific antisera. Our results point out that apoptotic cells experience significant reduction in the levels of the intermediate filament proteins, keratins-18, 19, vimentin and the associated 14-3-3 adapter proteins. At the same time, molecular chaperones such as glucose-regulated protein 94, calreticulin, calnexin, and protein disulfide isomerase exhibit marked accumulation in these dying cells. The present data indicate that apoptosis-associated processes in prostate epithelial cells include solubilization of the rigid intermediate filament network by specific proteolysis as well as increased levels of endoplasmic reticulum (ER) proteins with chaperone functions.

Differential expression of stathmin during neoplastic conversion of human prostate epithelial cells is reversed by hypomethylating agent, 5-azacytidine

In a variety of human tumor tissues, including those of prostate and breast, CpG hypermethylation represents one of the mechanisms downregulating the expression of specific proteins, including tumor suppressor proteins. Using 267B1-XR cells generated by ionizing radiation-induced transformation of epithelial cells, derived from neonatal human prostate and immortalized by SV40 (267B1), we now report markedly low levels of expression of the cytoplasmic phosphoprotein stathmin, in addition to several proteins of the actin microfilaments and intermediate filaments that characterize the altered phenotype. Stathmin is emerging as a relay protein integrating signals from diverse pathways during differentiation and neoplastic progression. In this in vitro prostate carcinogenesis model system, where loss of specific-protein expression is a major feature of the transformed 267B1-XR cells, we employed 5-azacytidine treatment followed by 2D-PAGE to reveal if experimental genomic hypomethylation reinstated the levels of any of the differentially expressed proteins. Our data suggest that stathmin represents one such example.

Detection of heterogeneity of apoptotic fragments of poly (ADP-ribose) polymerase in MDA-MB-468 breast cancer cells: two-dimensional gel analysis

Caspace-mediated proteolysis of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) (EC 2.4, 2.30) is a biochemical marker of cell death in response to various apoptotic stimuli. Anti-PARP antibodies identifying the 89 kDa polypeptide from the C-terminus as well as the 113 kDa native enzyme are often used to demonstrate evidence of apoptosis-associated, interleukin converting enzyme (ICE)-mediated limited cleavage. Recent evidence points to redundancy of caspases, heterogeneity of their cleavage sites, and a possibility of generating distinct context-specific, and cell-specific PARP fragments. In the present study, we employed antibodies directed to multiple sites in PARP and probed two-dimensionally resolved proteins of the estrogen receptor negative MDA-MB-468 breast tumor cells, induced to undergo apoptosis by ionizing radiation (IR). Our results revealed that the 24 kDa apoptotic fragment of PARP, from the N-terminus, consists of at least three isoforms, located at a p/more basic than the full length enzyme. We also report a hitherto unrecognized feature of an anti-PARP antiserum, VIC-5, detecting both the 89 kDa and the 24 kDa caspase-generated fragments of PARP. Thus, application of two-dimensional electrophoresis combined with antisera directed to multiple sites would be valuable in distinguishing PARP cleavage site- and inhibitor specificities of proteases during apoptosis.

Effects of collimator jaw setting on dose output for treatments with multileaf collimator

The variations in dose output with collimator jaw setting have been investigated for treatment fields shaped by a multileaf collimator. Measurements have been made for 6 and 15 MV x-ray beams on a Varian Clinac 2100C machine. The results of our study show that the collimator jaw settings can affect the dose by about 5% for a small field shaped by a multileaf collimator. The effect is smaller for larger fields.

Cytoskeletal changes during radiation-induced neoplastic transformation of human prostate epithelial cells

We recently reported tumorigenic transformation of SV40-immortalized neonatal human prostate epithelial cells (267B1) by exposure to fractionated doses of X-rays. Altered morphology and anchorage independence were observed following two successive fractions of 2 Gy each (F3-SAC). Additional 2 Gy treatments to these non-tumorigenic cells to a total dose of 30 Gy resulted in radiation-transformed tumorigenic colonies (267B1-SXR). Malignant transformation of parental 267B1 cells was also achieved by consecutive 2 Gy exposures to a total dose of 30 Gy (267B1-XR). This study discusses the cytoskeletal changes in the F3-SAC, 267B1-XR and 267B1-SXR derivatives of these human prostate epithelial cells. Confocal and conventional fluorescence microscopy of filamentous actin showed numerous, well organized, evenly distributed stress fibers in the parental cells prior to irradiation, while the anchorage-independent cells and several tumorigenic derivatives exhibited poor stress fiber organization after radiation exposure. This disorganization of actin microfilaments in the radiation-transformed cells was also accompanied by changes in the expression of selective tropomyosin isoforms as judged by two-dimensional gel electrophoresis. These changes in actin organization and tropomyosin expression appear to be coincidental with morphological transformation and acquisition of tumorigenicity in the 267B1 cells following radiation exposure.

Two-dimensional gel electrophoresis analyses identify nucleophosmin as an estrogen regulated protein associated with acquired estrogen-independence in human breast cancer cells

We have used two-dimensional gel electrophoresis to identify proteins associated with estrogen-induced proliferation in MCF-7 breast cancer cells and their progression to estrogen-independent proliferation. We compared the total cellular proteins from MCF-7 cells and an estrogen independent derivative of the MCF-7 cells MCF-7/LCC1 (Brünner et al. Cancer Research 1993, 53, 283-290), each grown with and without estradiol. These comparisons reveal seven estrogen-regulated proteins. Three of these proteins (HI-1: 36 kDa/pI 4.5, HI-10: 40 kDa/pI 5.5 and HI-19: 62 kDa/pI 5.0) exhibit a 'progression-like' pattern, being induced by estradiol in MCF-7 cells and constitutively present/upregulated in the MCF-7/LCC1 growing without estradiol. HI-11 (65 kDa/pI 5.5) is strongly induced by estradiol in MCF-7 cells but constitutively downregulated and unresponsive to estradiol in the MCF-7/LCC1 cells. Two proteins exhibit a suppressor pattern and are downregulated by estradiol in the estrogen-dependent MCF-7 cells (HI-3: 44 kDa/pI 4.4 and HI-4: 56 kDa/ pI 5.2) and present in MCF-7/LCC1 cells growing without estradiol at levels comparable to that seen in estrogen-treated MCF-7 cells. One protein (HI-9: 68 kDa/pI 5.5) exhibits a marked estrogen regulated pI shift, rather than changes in abundance. We purified and sequenced the HI-10 protein, which we identified as the nucleolar protein, nucleophosmin (NPM). One- and two-dimensional Western blot analyses of MCF-7/LCC1 cell lysates confirmed that HI-10 is immunoreactive with an antinucleophosmin antibody. Western blotting also confirmed the estrogenic regulation of NPM seen in the initial two-dimensional gel electrophoresis studies. Thus, NPM is induced by estradiol in the MCF-7 cells and upregulated in the MCF-7/LCC1 cells growing without estrogen, clearly associating its expression with an acquired estrogen-independent phenotype. NPM has several potentially important roles in regulating cell function and signaling. It is a substrate for phosphorylation by p34cdc2 kinase, protein kinase C and nuclear kinase II, and a repressor of the transcriptional regulating activities of both the IRF-1 tumor suppressor protein and the YY1 transcription factor. Studies are currently underway to determine which of these NPM functions may be involved in the hormonal progression of breast cancer.

Apoptosis-associated proteolysis of vimentin in human prostate epithelial tumor cells

Vimentin intermediate filaments (IF) are responsible for regulation of cell attachment and subcellular organization. Using an in vitro model system of human prostate epithelial cells (267B1-XR), we demonstrate that a series of vimentin proteolytic fragments represent some of the differentially expressed proteins in 2D-gel profiles of the apoptotic cells undergoing ionizing radiation-induced cell death. A caspase-sensitive motif search suggests that the type III IF protein (vimentin) is subject to proteolysis to promote the execution phase of apoptosis, in a manner similar to the well-established type V (lamins) and type I (keratins 18, 19) IF proteins. Furthermore, vimentin and a few of its derived polypeptides, reported to be specific to the apoptotic process, correspond to ubiquinated proteins, thus pointing to the complex interrelationships of protein ubiquination in solubilizing the IF network during apoptosis.

Laser-based microfocused x-ray source for mammography: feasibility study

A laser-produced plasma (LPP) x-ray source with possible application in mammography was created by focusing a laser beam on a Mo target. A Table-Top-Terawatt (TTT) laser operating at 1 J energy per pulse was employed. A dual pulse technique was used. Maximum energy transfer (approximately 10%) from laser light to hot electrons was reached at a 150 ps delay between pulses and the conversion efficiency (hard x-ray yield/laser energy input) was approximately 2 x 10(-4). The created LPP x-ray source is characterized by a very small focal spot size (tens of microns), Gaussian brightness distribution, and a very short pulse duration (a few ps). The spectral distribution of the generated x rays was measured. Images of the focal spot, using a pinhole camera, and images of a resolution pattern and a mammographic phantom were obtained. The LPP focal spot modulation transfer function for different magnification factors was calculated. We have shown that the LPP source in conjunction with a spherically bent, high throughput, crystal monochromator in a fixed-exit Rowland circle configuration can be used to created a narrow band tunable mammography system. Tunability to a specific patient breast tissue thickness and density would allow one to significantly improve contrast and resolution (exceeding 20 lp/mm) while lowering the exposure up to 50% for thicker breasts. The prospects for the LPP x-ray source for mammographic application are discussed.

Protein expression changes associated with radiation-induced neoplastic progression of human prostate epithelial cells

Carcinogenic progression in most epithelial systems is a multistep process and presents as numerous (un)stable intermediate stages prior to the development of a fully malignant phenotype. Recently, we reported the neoplastic transformation of an SV40 immortalized, neonatal human prostate epithelial cell line (267B1) by multiple exposures to X-rays [1, 2]. The parental 267B1 cells acquired anchorage-independence and exhibited morphological transformation following exposure to two consecutive doses of 2 Gy. Exposure of either the parental 267B1 cells or the anchorage-independent derivatives (F3-SAC) to a total dose of 30 Gy of X-rays yielded tumorigenic transformants (267B1-XR and 267B1-SXR, respectively). All of these radiation-treated derivatives (F3-SAC, 267B1-XR, and 267B1-SXR) were characterized by reduced cell size and poorly organized actin stress fibers [2, 3]. The present study examines the protein expression changes associated with cytoskeletal alterations during the different steps of neoplastic progression induced by X-rays in the in vitro human prostate cell system. This analysis was achieved by using the high resolving power of two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) in the 267B1, F3-SAC, 267B1-XR, and 267B1-SXR cells. We report changes in the expression of gelsolin in the partially transformed, anchorage-independent, nontumorigenic (F3-SAC) cells and a progressive loss of expression of tropomyosin isoforms (TM-1 and TM-3), and myosin light chain-2 (MLC-2) in the tumorigenic (267B1-XR; 267B1-SXR) cells, respectively. In contrast, our results demonstrate that the levels of the small GTP-binding protein Rho-A, an active participant in the actin stress fiber organization, are not altered during neoplastic progression of these 267B1 cells. Thus the changes in synthesis of gelsolin, tropomyosins, and MLC-2 provide a rationale for the alterations in the actin stress fiber formation and reduction in cell size during the exposure of prostate epithelial cells to multiple doses of X-rays.

Scatter reduction in mammography with air gap

Scatter reduction by air gaps in mammography was investigated. We have experimentally demonstrated that, independently of the imaging geometry, scatter in air-gap mammography can be well described by a virtual source of scatter (VSS) model. This model postulates that scatter radiation originates from a virtual point source of scatter placed on the central axis between the x-ray source and the exit surface of a patient at distance delta and utilizes only two parameters: delta and (S/P)0. The (S/P)0 parameter represents scatter-to-primary ratio without an air gap and delta is the distance from the exit surface of a patient to the virtual source of scatter. We have experimentally determined the analytical form of the two independent parameters of the VSS model; delta exhibits a linear increase proportional to the radiation field size, does not depend on patient thickness, and is in the 10-30 cm range, while (S/P)0 increases with the field size as a power function and is in the 0.4-1.3 range. In the framework of the VSS model the selectivity, the contrast improvement factor, and the signal-to-noise improvement factor were employed to evaluate performance of air-gap mammography systems. We have demonstrated that selectivity of an air gap rapidly deteriorates at some well-defined critical value of scatter fraction that has profound consequences on air-gap performance. Assuming fixed patient exposure, the results shows that, if a contrast limited detection system (such as film/screen mammography) is used, an air gap system can outperform a grid system only if a very large source-to-patient (SPD) distance is utilized, which might be possible with new laser-based x-ray sources. For the noise limited detection systems (such as digital mammography) even a small SPD (70 cm) and a small air-gap (20 cm) system will outperform a grid system.

Comparison of measured and calculated dose for asymmetric x-ray beams defined by independently movable collimators

Linear accelerators with x-ray collimators that move independently are becoming increasingly common for treatment with asymmetric fields. In an asymmetric field, the center of the treatment field is away from the true central axis where dosimetric data are normally obtained. In this paper we present a simplified approach to the calculation of dose for asymmetric fields. We use central axis tissue-maximum ratio, off-axis factor in phantom and relative field-size factor in phantom to calculate dose. The accuracy of our calculations has been compared with ion-chamber measurements for 6 and 15 MV x-ray beams. Measurements were made at 5, 10, and 15 cm off-axis for a 20 cm x 20 cm asymmetric field at dmax and 6 cm depths in a solid-water phantom using a 0.6 cc Farmer chamber. Agreement within 3% was found at the measurement points.

Radiation-induced neoplastic transformation of human prostate epithelial cells

We report the malignant transformation of human prostate epithelial cells (267B1) after multiple exposures to ionizing radiation. Carcinogenic progression of cells from immortal growth to anchorage-independent growth in soft agar to tumorigenicity in athymic mice resulted after a cumulative X-ray dose of 30 Gy. The tumors were characterized histologically as poorly differentiated adenocarcinomas, expressed prostate-specific antigen, and stained positive for keratin. No p53 or ras mutations were observed. Numerous chromosomal defects were noted on karyotypes after radiation exposure. However, chromosome 3 and 8 translocations were observed predominantly in the tumor outgrowths. These findings provide the first evidence of malignant transformation of human prostate epithelial cells exposed to ionizing radiation.

Surface dose for tangentially incident photon beams in the presence of air gap and air cavity

Dose to a surface parallel to an incident photon beam has been investigated in the presence of air gaps and air cavities. Measurements have been made in an acrylic phantom with a parallel plate chamber. Photon beams of Co 60, 4-MV, 6-MV, and 15-MV X-rays have been investigated. The results of our measurements show that in the case of air gaps, the dose reduction to a tangential surface is considerable. On the other hand, the dose reduction is 2% or less in the case of air cavity for volumes encountered in clinical situations.

Analysis of mannoproteins from blastoconidia and hyphae of Candida albicans with a common epitope recognized by anti-complement receptor type 2 antibodies

Mannoproteins of approximately 50 kDa from blastoconidia and 60 kDa from hyphae of Candida albicans reacted in Western blots (immunoblots) with either a polyclonal rabbit antiserum (CA-7) or a monoclonal antibody (CA-A) to the C. albicans C3d-binding protein (complement receptor type 2). The glycosylated nature of these proteins was demonstrated by their reactivity with concanavalin A and by selective labeling with the biotin-hydrazide reagent following periodate oxidation. Differences in the oligosaccharides of these proteins were observed in regard to their reactivity with lectin-peroxidase reagents and sensitivity to glycosidases such as N-glycanase or endoglycosidase F (but not endoglycosidase H). The 60-kDa mannoprotein reacted with wheat germ agglutinin, while the 50-kDa mannoprotein did not. Treatment of the 60-kDa mannoprotein with the glycosidases mentioned above resulted in its conversion into a species of 40 to 45 kDa. Enzyme treatment had no obvious effect on the electrophoretic mobility of the 50-kDa species from blastoconidia. Both the 50- and 60-kDa glycoproteins remained immunoreactive after treatment with the glycosidases. Reactivities of the two mannoproteins to neuraminidase also differed. Finally, the 50-kDa (blastoconidia) and the 60-kDa (hyphae) mannoproteins were purified by using ion-exchange chromatography and electroelution. The purified proteins differed in net charge, the 60-kDa species having a more acidic pI. Functional activity of the purified mannoproteins was demonstrated, as each inhibited the rosetting of antibody-sensitized sheep erythrocytes conjugated with iC3b or C3d by hyphae. Thus, an epitope(s) common to both a mycelial and blastoconidial mannoprotein is associated with a structurally different oligosaccharide for each growth form.

A simple approach to the technical aspects of radiosurgery treatments

An approach to radiosurgery treatment that can be readily adopted in most radiotherapy centers with linear accelerators is presented. In our institution, a Leksell-type of neurosurgical frame, a computed tomography scanner, locally fabricated cones, and 6 MV X-ray beams are used to perform radiosurgery treatments. Collimated arcs with dose distributions, that conform to the shape of the lesion in the transverse and the sagittal planes are used. It is argued that the uncertainties in the localization of the isocenter within a lesion and the specifications of the size of the target volume do not justify high precision mechanical devices for most radiosurgery treatments.

High-resolution two-dimensional electrophoresis of nuclear proteins: A comparison of HeLa nuclei prepared by three different methods

A comparative analysis of HeLa cell nuclear proteins is presented using Iso-Dalt methods of protein resolution in two dimensions. The nuclear proteins were prepared by (1) spin through glycerol cushion, (2) spin through sucrose cushion, or (3) Triton wash. Improved resolution of total nuclear proteins in the range of pH 4.5-6.0 was achieved by substituting longer isotubes in combination with broad-range ampholines during the isoelectric focusing step. An attempt to indicate silver stainable protein spots common to total cellular extracts and nuclear preparations has been made. Also, proteins that appear to be well represented in all three nuclear preparations and remain undetectable in the total cellular protein pattern have been marked as probably being enriched nuclear proteins. Such a comparative analysis of whole nuclear protein preparations made it possible to document that the different preparations preserved the same set of proteins. The Triton-wash method of obtaining nuclei was identified as the preferred choice. Coomassie-stained gels and blots of these nuclear proteins could serve as a guide for accessing relevant protein spots for further biochemical analysis such as immunoblotting.

Comparison of absorbed doses in water and solid water for electron beams

Solid water, as a substitute for water, has become commercially available for dosimetry measurements. A study was undertaken to compare the dose in water and solid water respectively for 6, 9, 12, 16 and 20 MeV electron beams. Measurements using ion chamber show that the dose in water is higher than the dose in solid water by 1% for 6, 9, and 12 MeV electrons. For 16 and 20 MeV electrons, the dose in water and solid water are the same within the uncertainty of our measurements.

Linear quadratic model and biologically equivalent dose for single fraction treatments

The linear quadratic model has been used to calculate the biologically equivalent dose for single fraction treatments. Our calculations suggest that for late reacting tissue, such as the brain, a single fraction of 1440 cGy is equivalent to a conventional treatment of 5000 cGy in 25 fractions.

Pitfalls in dose calculation using a commercial treatment planning computer for Clinac-4 4MV x-ray beam

Dose calculations on a commercial treatment planning computer based on the storage of profile data along a principal axis for Clinac-4 4MV x-ray can lead to significant error in calculated dose in the corners of a large field. These errors are due to the unique nature of the lead flattening filter on Cl-4. A method is suggested to remedy this problem by storing profile data along a diagonal of a large field.

Corner transmission in several linear accelerator photon beams

Maximum x-ray field sizes on many linear accelerators are obtained only with truncated corners. Transmissions through the corners of such fields has been measured utilizing film and ion chamber dosimetry for a number of accelerators. Transmissions are found to be significantly larger than for the movable jaws.

Determination of dose enhancement in cortical bone substitute material for electron beams

Dose measurements in Witt liquid, which simulates cortical bone, have been compared with dose in water for 6-, 9-, 12-, and 15-MeV electron beams. Measurements were made using a Farmer ionization chamber. The results of the study show dose enhancement in Witt liquid of 5%, 7%, 4%, and 0.4% for 6-, 9-, 12-, and 15 MeV electrons at shallow depths. The dose to a small mass of soft tissue in bone has also been estimated using ionization measurements. The results show a significantly higher dose in bone.

Dosimetry of I-125 seeds implanted on the surface of a cavity

Dosimetry of a new implant technique to treat brain tumors is presented. High grade gliomas or astrocytomas are surgically removed, and radioactive I-125 seeds are implanted on the surface of the cavity. A computational model is presented to determine the number of seeds and the activity of the seeds for a given dose and cavity size.

Constraints to DNA unwinding near radiation-induced strand breaks in Ewing's sarcoma cells

Ewing's sarcoma cell lines were compared to other cell lines for induction of DNA strand breaks by ionizing radiation and their ability to repair those breaks. The alkali-unwinding assay and alkaline sucrose gradient analysis were used for these studies. The alkali-unwinding assay revealed that the amount of DNA unwound per strand break in Ewing's sarcoma cells was less than for other cells and was not influenced by high-salt denaturation conditions. Ewing's sarcoma cells had similar induction and repair rates for strand breaks compared with other cell lines. The kinetics of unwinding suggests there are constraints to DNA unwinding in the chromatin of Ewing's sarcoma cells, possibly related to high levels of poly(ADP-ribose) polymerase in these cells.

Enhanced poly(adenosine diphosphate ribose) polymerase activity and gene expression in Ewing's sarcoma cells

Ewing's sarcoma (ES) is a highly malignant childhood bone tumor and is considered curable by moderate doses of radiotherapy. The addition of chemical inhibitors of the activity of the nuclear enzyme poly(adenosine diphosphate ribose) [poly(ADPR)] polymerase to ES cells in culture results in increased cell killing, a phenomenon called "inhibitor sensitization." Since poly(ADPR) polymerase is thought to be associated with DNA repair, it has been suggested that ES cells and other inhibitor-sensitized cells may have a reduced capacity for polymer synthesis resulting in deficient postirradiation recovery. We present here the unexpected observation that in comparison to other cell lines tested, ES cells exhibit a high enzyme activity, higher constitutive levels of the protein, and elevated levels of its mRNA transcript for poly(ADPR) polymerase. No gross amplifications or rearrangements of the gene were observed; however, regulation of poly(ADPR) polymerase in these tumor cells takes place at the level of the gene transcript.

Quantitation of strand breaks in human DNA using 32P-Alu hybridization: application to exponential and plateau-phase cells

A sensitive quantitation of DNA (0.2 to 10 ng) can be achieved using a 32P-labeled Alu probe to hybridize human DNA spotted onto nylon membrane. This allows the determination of radiation-induced single-strand breaks without the use of [3H]thymidine prelabeling of cells in culture. The sensitivity of this technique in HeLa cells is comparable to results obtained using the alkaline unwinding technique. The method is applicable to cells in both exponential and plateau phases of growth.

Comparison of absorbed dose in bone substitute material and water using ionization measurements

Absorbed dose in a liquid substitute for bone has been compared with absorbed dose in water for 9-, 12-, and 15-MeV electron beams using ionization chamber measurements. The ionization readings were converted to dose using collisional mass stopping power ratios. The collisional mass stopping powers for the liquid substitute of bone were calculated using the Monte Carlo Code PEGS4. The results of our study show that there is an increase in dose in the liquid bone substitute compared to water at shallow depths. The maximum increase in dose was 5%, 4%, and 2% at depths of 1.2, 1.5, and 2.0 cm, respectively, for 9-, 12-, and 15-MeV electrons. The density of the liquid bone substitute was 1360 kg/m3 and the effective atomic number was 11.

Dose distribution for 125I implants due to anisotropic radiation emission and unknown seed orientation

Variations in dose distribution due to anisotropic radiation emission around 125I seeds and a lack of knowledge about the orientation of the implanted seeds have been investigated. Upper and lower bounds for dose distributions have been calculated for planar implants using the experimentally determined angular dose distribution around a typical 125I seed. Results of our study suggest that significant dose variations in the center and the periphery of the implanted area are possible.

Radiation protection considerations for endocavitary X ray units

Application of a contact X ray therapy unit for endocavitary irradiation of selected rectal carcinomas is gaining acceptance as a treatment of choice. The patient is placed on a proctoscopic table in the surgical suite and the anus is anesthetized and dilated to allow insertion of a 3 cm diameter proctoscope designed to admit the X ray tube. The measured half-value layer for 50 kVp X rays filtered by 1.0 mm of aluminum was determined to be 0.65 mm of aluminium. The dose rate at the end of the 4.0 cm source-skin-distance (SSD) cone was measured to be on the order of 1000 rad/minute. Radiation surveys performed for several treatment geometries indicate that exposure rate levels in the environs immediately around the patient can be quite high. Radiation measurements were made for the following locations: where the radiotherapist stands holding the X ray tube; at the side of the patient where the technologist or any supporting personnel might stand; and at the patient's posterior surface in the direction where the anesthesiologist might stand. Radiation levels ranged from 0.001 to 1.0 roentgen (R) per hour and depend primarily on the depth and angle of the X ray tube inserted into the rectum.

Lung density effect on 125I dose distribution

Perturbations in 125I implant dose distribution due to lung tissue variations have been investigated. Dose correction factors for a point source, a planar, and a volume implant have been calculated using a model which accounts for the changes in primary photon attenuation and in buildup factor when the medium is lung rather than water. Results of our calculation show that the change in dose is about 9% and 20% in the core and the periphery, respectively, of a representative implanted volume whose density is 0.25 relative to water.

Low-density lipoprotein receptor binding determinants switch from apolipoprotein E to apolipoprotein B during conversion of hypertriglyceridemic very-low-density lipoprotein to low-density lipoproteins

Using thrombin and trypsin as probes, we determined: first, that low-density lipoprotein (LDL) receptor binding determinants switch from apolipoprotein (apo) E to apo-B within the very-low-density lipoprotein (VLDL) Sf 20-60 region of the metabolic cascade from VLDL1 (Sf 100-400) of hypertriglyceridemic (HTG) human subjects to LDL. Second, two different conformations of apo-E exist in HTG-VLDL Sf greater than 60, one accessible (greater than or equal to 1 mol/mol of particle) and one inaccessible (1-2 mol/mol) to both thrombin and the LDL receptor; normal VLDL (Sf greater than 60) have only the inaccessible conformation and therefore do not bind to the LDL receptor. Third, thrombin degrades apo-B into large fragments, three of which have electrophoretic mobilities similar to B-48, B-74, and B-26; this, however, has no effect on apo-B-mediated receptor binding. Fibroblast studies showed that thrombin could abolish receptor uptake of HTG-VLDL1 and HTG-VLDL2 (Sf 60-100), had little or no effect on HTG-VLDL3 (Sf 20-60), and no effect on uptake of intermediate-density lipoprotein (IDL) or LDL. Trypsin abolished the binding of HTG-VLDL1 and HTG-VLDL2, reduced that of HTG-VLDL3, but had little to no effect on IDL or LDL binding. Immunochemical techniques revealed that thrombin cleaved some apo-E into the E-22 and E-12 fragments; after trypsin treatment no apo-E was detected in any HTG-lipoprotein. Normal VLDL subclasses contained less apo-E than the corresponding HTG-VLDL subclasses and it was not cleaved by thrombin. Apo-B immunoreactivities of VLDL subclasses were not significantly changed after treatment with thrombin, although thrombin cleaved some of the B-100 of each VLDL subclass, and all apo-B in IDL and LDL, into 4-6 major large fragments. Trypsin converted all of the apo-B of each lipoprotein into smaller fragments (Mr less than 100,000). We conclude that apo-E of the thrombin-accessible conformation mediates uptake of HTG-VLDL1 and HTG-VLDL2 but that apo-B alone is sufficient to mediate receptor binding of IDL and LDL; the switch from apo-E to apo-B as the primary or sufficient binding determinant occurs within the VLDL3 (Sf 20-60) region of the metabolic cascade, where receptor binding first appears in VLDL subclasses from normal subjects.

Dose enhancement in bone in electron beam therapy

This study investigated dose to bone tissue in electron beam therapy. Measurements were made using films and thermoluminescent dosimeters in a polystyrene phantom containing bone inhomogeneity for 15-MeV, 12-MeV, and 9-MeV electron beams. An increase in dose of approximately 18%, 12%, and 11%, for the three electron energies respectively, relative to the dose in polystyrene, was found for bone material having an electron density (relative to water) of 1.73. Measurements were also made using films for 15- and 9-MeV electrons in a phantom with a mandibular bone and teeth. A dose enhancement in bone of approximately 10% and 7%, respectively, for the two energies was found in the phantom where the electron density of bone was about 1.60. These results suggest that injury to bone is possible in those clinical situations where high doses of electrons are used for therapy.

Calculation of dose in off-central axis planes using off-axis ratios

Accuracy of dose calculation for regular fields in off-central axis planes was investigated on a RAD-8 treatment planning computer for 4- and 10-MV x-ray beams produced by Varian Clinac -4 and Clinac -18 linear accelerators. These calculations, which are based on central axis depth dose and off-axis ratios in the principal planes, can be in error by as much as 25%-30% at locations well within the irradiated volume for the 4-MV x-ray beam. These large errors for the Clinac -4 beam result from the falloff in dose beyond the peak dose along a diagonal of a large field at distances greater than 14 cm from the central axis due to the lead flattening filter. The profile data stored in the computer along the principal planes cannot be used to calculate the dose accurately in such a situation. Computed doses for the 10-MV x-ray beam agreed with the measured doses within 4%-6% at all locations.

Buildup factors and dose around a 137Cs source in the presence of inhomogeneities

The effect of inhomogeneities on dose near a gamma-ray source has been investigated. Experimental measurements were made with a 137Cs source in a polystyrene phantom at a distance of 5 cm from the source. Inhomogeneities consisted of 2-cm-thick slabs interposed between the source and the plane of measurement. Dose correction factors (DCF) for 2-cm-thick aluminum, bone, lung, and air have been determined. Our results show that for 137Cs source the dose correction factors are of the order of 3% to 8%. A theoretical model for calculation of dose correction factor in brachytherapy in the presence of inhomogeneities has been developed. The model calculates DCF using buildup factors for the water-equivalent path between the source and the point of calculation. Good agreement was found between calculations and experimental measurements.

Lung dose in electron beam therapy of chest wall

The dose to lung tissue in patients whose chest walls are irradiated with 6 and 9 MeV electron beams was estimated. Thermoluminescent dosimetry measurements in thoracic Section 18 of Rando phantom were compared with calculations by two different methods, the effective depth method and the average absorption equivalent thickness (AET) method. The calculations were based on a density of 0.45 (relative to water) for lung tissue in the Rando phantom which was determined from CT scan. The measurements agreed with calculations by the effective depth method within 7 per cent for 9 MeV electron beam at locations where lung tissue thickness was less than 4.5 cm. Larger discrepancy between measurement and calculations was found at greater depths. The effective depth method gave better agreement with measurements (within 14 per cent) compared with the average AET method. The effective depth method was used, to calculate the lung tissue dose at different depths beneath the chest wall. A lung density of 0.25 was assumed to conform to real irradiation situation. The calculations show that for a 9 MeV electron beam dose to lung at 5 cm depth beyond a 2 cm thick chest wall could be as high as 72 per cent of the dose at the maximum buildup depth. It is recommended that post-mastectomy patients with chest wall thickness less than 2 cm should be irradiated with an electron energy of less than 9 MeV or that the chest wall thickness be artificially increased with tissue equivalent bolus.

Computed tomography in definitive radiotherapy of prostatic carcinoma, part 2: definition of target volume

Pretreatment computed tomography (CT) scanning of the pelvis was performed in 100 consecutive patients with carcinoma of the prostate treated with external irradiation (82 patients) or interstitial I125 (18 patients). Treatment plan modifications prompted by CT scan findings were most frequent in patients with (clinical) involvement of the seminal vesicles in whom the conventional treatment planning often resulted in an underestimate of tumor volume. Seventeen of 32 (53%) such patients required an enlargement of treatment fields to adequately encompass the target volume. Using skeletal landmarks as reference, the dimensions of the prostate, seminal vesicles and the detectable tumor and their topographic relationships were systematically tabulated. These measurements provide a basis for the definition of the target volume in patients with carcinoma of the prostate in whom CT scans might not be available.

Contribution of CT to quantitative radiation therapy planning

The contribution of computed tomography (CT) in radiotherapeutic treatment of lung cancer was evaluated. Radiation therapy ports prepared for 50 patients on the basis of routine diagnostic radiographs and without CT scan information were reviewed after CT scanning. Of 50 patients, 13 (26%) required alteration of treatment ports on the basis of the additional CT scan information. In 11 patients (22%) the changes resulted in an increase in field size to cover the tumor adequately, and in two patients (4%-) the field size was reduced to spare normal tissue. A three-phase study was completed to evaluate the impact of CT on quantitative parameters of two-dimensional treatment plans on 25 of the 50 patients. Treatment plans in the absence of CT scan and without lung transmission correction were compared with treatment plans where CT information was used and lung transmission corrections were performed. Numerical results for local efficiency and nonuniformity factor were compared for conventional, CT unoptimized, and CT optimized plans. Of the 25 patients, 14 (56%) had poorer local efficiency and 16 (64%) had nonuniformity factor exceeding 5% when treatment was planned without CT information. CT-optimized plans improved local efficiency in 16 (64%) of 25 patients and reduced nonuniformity to within 5% in 21 (84%). It is suggested that in the treatment planning of patients with lung cancer, CT scan information is essential for accurate determination of dose distribution and optimization of therapy.

Effects of focal spot intensity distribution and collimator width in reconstructive x-ray tomography

In computed tomography the finite width of the collimator aperture implies that the image is reconstructed from scans having finite strip width. This blurs the image and limits scanner resolution. Bracewell has discussed the nature of the blurring produced and suggested a method to partially restore the image under the assumption that the x-ray focal spot has a uniform intensity distribution. However, pinhole radiographs of x-ray focal spots reveal intensity distribution in the scanning plane which peaks at the edges of the focal spot with a reduced intensity in the center. A model is presented which simulates this intensity distribution as the sum of two point sources of x rays separated by a uniform line source. This results in a point absorber response function which is a superposition of two rectangular distributions and the one discussed by Bracewell. The corresponding tranfer function is derived which shows that the intensity distribution of the focal spot influences the high spatial frequency components of the reconstructed image more than the low frequency components.

Dosimetric evaluation of a computed tomography treatment system

Pixel-by-pixel correction for tissue inhomogeneities was performed with a CT-interfaced treatment planning system. The CT number for each pixel was converted to a physical density. Comparison of the resulting data with dose measurements in a RANDO phantom shows that pixel calculation overestimates dose by 5--7% at locations adjoining the lung, where loss of scatter is not taken into account by the algorithm. However, the new system does have some advantages over conventional treatment planning systems.