Post-exposure Growth Research Articles

Assessment of stereotactic high-resolution detectors for stereotactic body radiotherapy: comparative analysis between myQA® SRS and Gafchromic EBT-XD films.

The study aimed to evaluate dosimetry systems used for stereotactic body radiotherapy (SBRT), specifically 2D array dosimetry and film dosimetry systems, for exploring their characteristics and clinical suitability. For this, high-resolution myQA SRS detectors and Gafchromic EBT-XD films were employed. Film analysis included net optical density (OD) values depending on energy, dose rate, scanner orientation, scanning side, and post-exposure growth. For myQA SRS, signal values were evaluated in terms of dose rate (400-1400 MU/min) and angular dependence (0-180° at 30° intervals) along with couch angles of 0°, 45°, and 90°. Pre-treatment verification included 32 SBRT patients for whom myQA SRS results were compared with those obtained with Gafchromic EBT-XD films. Analysis revealed less than 1% deviation in net OD for energy and dose rate dependence. Scanner orientation caused 2.5% net OD variation, with minimal differences between film front and back scan orientations (variance < 1.0%). A rapid OD rise occurred within six hours post-exposure, followed by gradual increase. The myQA SRS detector showed -3.7% dose rate dependence (400 MU/min), while the angular dependence at 90° was -26.7%. A correction factor effectively reduced these differences to < 1%. For myQA SRS, gamma passing rates were-93.6% (2%/1mm), while those for EBT-XD films were-92.8%. Improved rates were observed with 3%/1mm: for myQA SRS-97.9%, and for EBT-XD film-98.16%. In contrast, for 2%/2mm with 10% threshold, for myQA SRS-97.7% and for EBT-XD film-98.97% were obtained. It is concluded that both myQA SRS detectors and EBT-XD films are suitable for SBRT pre-treatment verification, ensuring accuracy and reliability. However, myQA SRS detectors are preferred over EBT-XD film due to the fact that they offer real-time measurements and user-friendly features.

In vitro inactivation of SARS-CoV-2 by ozonated water via novel hand hygiene device.

The COVID-19 pandemic has heightened awareness of the need for novel surface disinfectants and hand-hygiene modalities. Ozone gas is an effective surface disinfectant, but toxicity limits its use in human applications. Ozonated water is a safer means to use ozone for disinfection, especially for human antisepsis. However, there are little data available regarding the effectiveness of ozonated water in eliminating severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). This study utilizes a novel hand hygiene device that produces a stable ozone concentration of 0.5 +/-0.1ppm in water and applies it using a proprietary spray that controls droplet size, velocity, and direction. The Device was used to apply ozonated water to a known quantity of SARS-CoV-2 Delta Variant viral particles on a non-porous surface (glass) for seven seconds. Post-exposure growth was compared to the unexposed matched control utilizing the Spearman-Karber method. Compared to control, ozonated water decreased SARS-CoV-2 viral growth by a mean log10 reduction of 4.33, or>99.99%reduction. These results suggest that the ozonated water, when applied by a spray hand hygiene device, is highly effective at surface disinfection of SARS-CoV-2.

Rhenium Perrhenate (188ReO4) Induced Apoptosis and Reduced Cancerous Phenotype in Liver Cancer Cells.

Recurrence in hepatocellular carcinoma (HCC) after conventional treatments is a crucial challenge. Despite the promising progress in advanced targeted therapies, HCC is the fourth leading cause of cancer death worldwide. Radionuclide therapy can potentially be a practical targeted approach to address this concern. Rhenium-188 (188Re) is a β-emitting radionuclide used in the clinic to induce apoptosis and inhibit cell proliferation. Although adherent cell cultures are efficient and reliable, appropriate cell-cell and cell-extracellular matrix (ECM) contact is still lacking. Thus, we herein aimed to assess 188Re as a potential therapeutic component for HCC in 2D and 3D models. The death rate in treated Huh7 and HepG2 lines was significantly higher than in untreated control groups using viability assay. After treatment with 188ReO4, Annexin/PI data indicated considerable apoptosis induction in HepG2 cells after 48 h but not Huh7 cells. Quantitative RT-PCR and western blotting data also showed increased apoptosis in response to 188ReO4 treatment. In Huh7 cells, exposure to an effective dose of 188ReO4 led to cell cycle arrest in the G2 phase. Moreover, colony formation assay confirmed post-exposure growth suppression in Huh7 and HepG2 cells. Then, the immunostaining displayed proliferation inhibition in the 188ReO4-treated cells on 3D scaffolds of liver ECM. The PI3-AKT signaling pathway was activated in 3D culture but not in 2D culture. In nude mice, Huh7 cells treated with an effective dose of 188ReO4 lost their tumor formation ability compared to the control group. These findings suggest that 188ReO4 can be a potential new therapeutic agent against HCC through induction of apoptosis and cell cycle arrest and inhibition of tumor formation. This approach can be effectively combined with antibodies and peptides for more selective and personalized therapy.

Responses of bay anchovy (Anchoa mitchilli) larvae under lethal and sublethal scenarios of crude oil exposure

Bay anchovy (Anchoa mitchilli) is an ecologically important zooplanktivorous fish inhabiting estuaries of the Gulf of Mexico and eastern North America from Maine to Florida. Because they have a protracted spawning season (spring through fall) and are abundant at all life stages in coastal estuaries, their eggs and larvae likely encountered oil that reached the coast during the Deepwater Horizon oil spill. We compared responses to oil exposure at different life stages and at lethal and sublethal conditions using acute, 24h exposures. In a series of experiments, bay anchovy larvae were exposed to high energy water accommodated fractions (HEWAF) and chemically-enhanced WAF (CEWAF) at two stages of larval development (5 and 21 days post hatch, dph). HEWAF oil exposures induced significantly greater life stage dependent sensitivity at 5 dph than at 21 dph but chemically dispersed (CEWAF) exposure mortality was more variable and LC50s were not significantly different between 5 and 21dph larvae. Acute exposure to two low-level concentrations of CEWAF did not result in significant mortality over 24h, but resulted in a 25–77% reduction in larval survival and a 12–34% reduction in weight specific growth after six days of post-exposure growth following the initial 24h exposure. These results show that younger (5 dph) bay anchovy larvae are more vulnerable to acute oil exposure than older (21 dph) larvae, and that acute responses do not accurately reflect potential population level mortality and impacts to growth and development.

Trajectory and Predictors of Alliance in Cognitive Behavioral Therapy for Youth Anxiety

Multilevel growth analysis was used to establish the shape of change (mean growth trajectory) for youth- and therapist-rated alliance in cognitive behavioral therapy (CBT) for anxious youth and to identify between-youth predictors of alliance trajectory. Youth (N = 69; ages 7–17; 52.2% female) and their parents participated in an empirically supported CBT protocol. Therapists rated alliance each session and youth every four sessions. Data were fit to four growth models: linear, quadratic, a dual slope, and a novel “alliance rupture” model. Two-level models were estimated to examine the effect of youth age, sex, pretreatment symptom severity, diagnostic comorbidity, early treatment factors (use of Selective Serotonin Reuptake Inhibitors), and coping styles (engagement, disengagement, and involuntary coping). A dual slope model fit therapist data best, whereas youth data did not evidence systematic growth. Two-level growth models identified that pretreatment anxiety severity predicted higher initial alliance levels. Depressive symptoms predicted less linear growth and engagement coping predicted greater growth during exposure sessions. No variables predicted preexposure growth. In the therapist model, 22% of initial alliance, 50% of preexposure growth, and 75% of postexposure growth were accounted for by between youth variables (mood disorder, anxiety and depression symptoms, engagement and involuntary coping). Therapist-reported alliance ratings may grow over the course of manual-based CBT, even during exposure-focused sessions. Pretreatment youth factors and coping style may influence the absolute value and linear trajectory of alliance during CBT. Findings about alliance-influencing factors can help set expectations for, and enhance training in, empirically supported treatments.

Characteristics of Gafchromic XRQA2 films for kV image dose measurement

In this study, the relevant characteristics of the new Gafchromic XRQA2 film for its application in measuring kV cone beam computed tomography (CBCT) image doses were thoroughly investigated. The film was calibrated free in air to air kerma levels between 0 and 9 cGy using 120 kVp photon beams produced by the x-ray volume imager. Films were scanned using transmission and reflection scanning modes with the Epson Expression 10000 XL flat-bed document scanner. The impact of film size, region of interest for the analysis, scan uniformity, scan resolution, scan orientation and alternate scanning sides on the analysis process were investigated. Energy dependence, postirradiation growth of reflectance with time and irradiation angular dependence of the film were tested at different air kerma levels. The net reflectance changed by ∼3% when the size of the film piece changed from 1 cm × 2 cm to 10 cm × 11 cm and changed by ∼1% when ROI changed from 0. 7 cm × 0. 7 cm to 8 cm × 8 cm, suggesting a good uniformity of the film. The film was successfully analyzed using the transmission scanning mode, calibration curves from both transmission and reflection scanning modes showed similar behavior. The calibration uncertainty was somewhat lower when the film was scanned using reflection mode (6% and 8% for reflection and transmission modes, respectively.) Higher scanning resolution came with increasing calibration uncertainty. The calibration uncertainty for reflection and transmission modes increased from ∼3.5% to 7% and from ∼3.5% to 9%, respectively when scanning resolution was changed from 50 to 400 dpi. Scanning the film on alternate sides using transmission mode led to variation of 16%-19% in the net optical density at doses commonly used for CBCT procedures. The film response changed by almost 10% when it was exposed to beams of two different energies (100 and 120 kVp.) Other features of the film such as film orientation, postexposure growth, and irradiation angular dependence were also investigated. The size of film piece and analysis ROI used for calibration slightly affected the film response. Both transmission and reflection scanning modes can be used to analyze the Gafchromic XRQA2, with the reflection mode having a somewhat lower calibration uncertainty. Scanning films on alternate sides using transmission mode significantly affects the optical density. The film response was shown to be energy dependent. The films reached stability in about 6 h after exposure. The film response was proven to be independent of irradiation angle except when the beam is parallel to the film surface.

Characteristics of Gafchromic® XR‐RV2 radiochromic film

Gafchromic XR-RV2 is a revised version of the obsolete Gafchromic XR-R-type radiochromic film. This article investigates the dose response, energy response, postexposure growth, and polarizing effects of this film after exposure to ionizing radiation in the diagnostic energy range. The effect of bit depth on scanning was also investigated. Films were scanned using an Epson Expression 10000XL document scanner or an X-Rite model 301 spot densitometer. Color channel analysis was performed. The film showed usable response in the air kerma range of 1-1000 cGy, although by 1500 cGy the film appeared saturated when using the red color channel on a document scanner. The film response varied by 11% between 60 and 96 kVp and 3.5% between 96 and 125 kVp for doses above 1 Gy. Postexposure growth was found to be approximately logarithmic and fairly stable after 24 h. Films stored under office lighting exhibited around twice the density growth compared with film stored in a dark environment. The film showed strong orientation dependence when scanned using a polarized light source. A 48 bit scan provided no increase in sensitivity over 24 bits. Gafchromic XR-RV2 film is a radiochromic film ideally suited for measurement of wide dose ranges at diagnostic energies. The energy dependence of this film limits its accuracy for dosimetry of unknown energy beams. For the document scanners used in this study a 24 bit scan was more than sufficient compared to a 48 bit scan. This is likely to be the case for most document scanners where electrical noise prevents higher bit depths from increasing the sensitivity of measurements.

Optimal densitometry wavelengths that maximize radiochromic film sensitivity while minimizing OD growth and temperature sensitivity artifacts

It is well known that optical density (OD) of the radiochromic film (RCF) continues to grow after exposure at rates that have a complex dependence on dose, temperature, and densitometry wavelength. Dose rate and fractionation artifacts associated with variations in OD growth may limit the accuracy achievable by RCF dosimetry in brachytherapy and external beam applications, particularly at low doses (<5 Gy) and low dose rates (<10 cGy/h) where OD growth and sensitivity effects are large. To identify densitometry wavelengths that minimize OD growth artifacts and enhance RCF sensitivity at low doses, we have investigated Model MD-55-2 RCF response as a function of densitometry wavelength, irradiation-to-densitometry time interval, dose and temperature. Using a Perkin Elmer spectrophotometer, the absorption spectrum in the 500-700 nm range was measured for doses ranging from 1-100 Gy, over post-irradiation times from 1 h to 60 days. An empirical model with time-independent, fast and slow growth components was used to fit single exposure data and the dependence of the resulting best-fit parameters on dose and densitometry wavelength was investigated. RCF OD variation with temperature in the range 22-40 degrees was measured. Wavelengths in the 660-690 nm range were found to minimize the dose-dependence of OD post-exposure growth. Densitometry wavelengths in the range of 670-680 nm enhance RCF sensitivity and show small variations in OD with temperature in the range from 22-40 degrees. Compared to 633 nm light, 675 nm densitometry reduces OD growth at 1 Gy from 70% to 10% over a period of nearly 1174.0 h relative to the initial OD measured at 1.7 h post-irradiation. In addition, RCF sensitivity is nearly doubled at this wavelength for all dose levels.

A Synthetic Congener Modeled on a Microbicidal Domain of Thrombin- Induced Platelet Microbicidal Protein 1 Recapitulates Staphylocidal Mechanisms of the Native Molecule

Thrombin-induced platelet microbicidal protein 1 (tPMP-1) is a staphylocidal peptide released by activated platelets. This peptide initiates its microbicidal activity by membrane permeabilization, with ensuing inhibition of intracellular macromolecular synthesis. RP-1 is a synthetic congener modeled on the C-terminal microbicidal alpha-helix of tPMP-1. This study compared the staphylocidal mechanisms of RP-1 with those of tPMP-1, focusing on isogenic tPMP-1-susceptible (ISP479C) and -resistant (ISP479R) Staphylococcus aureus strains for the following quantitative evaluations: staphylocidal efficacy; comparative MIC; membrane permeabilization (MP) and depolarization; and DNA, RNA, and protein synthesis. Although the proteins had similar MICs, RP-1 caused significant killing of ISP479C (<50% survival), correlating with extensive MP (>95%) and inhibition of DNA and RNA synthesis (>90%), versus substantially reduced killing of ISP479R (>80% survival), with less MP (55%) and less inhibition of DNA or RNA synthesis (70 to 80%). Interestingly, RP-1-induced protein synthesis inhibition was equivalent in both strains. RP-1 did not depolarize the cell membrane and caused a relatively short postexposure growth inhibition. These data closely parallel those previously reported for tPMP-1 against this strain set and exemplify how synthetic molecules can be engineered to reflect structure-activity relationships of functional domains in native host defense effector molecules.

Differential resistance to extended copper exposure in four introduced bryozoans

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 311:103-114 (2006) - doi:10.3354/meps311103 Differential resistance to extended copper exposure in four introduced bryozoans Richard F. Piola*, Emma L. Johnston School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia *Email: r.piola@unsw.edu.au ABSTRACT: Resistance to copper by some fouling species may have the 2-fold effect of both facilitating the introduction of nonindigenous species via the painted hulls of vessels, and providing these species with a competitive advantage in ports or estuaries already exposed to anthropogenically elevated copper concentrations. This study tested the tolerance of 4 introduced bryozoans, Bugula neritina, Watersipora subtorquata, Schizoporella errata and Tricellaria occidentalis, to a range of Cu concentrations (0, 10, 50, 100 and 500 µg l–1). Larval attachment after 24 h was not found to be a reliable indicator of post-metamorphic survival. Recruits of all species survived in 0 and 10 µg l–1 Cu for 20 d, with only Bugula neritina and Watersipora subtorquata recruits surviving exposure to 50 and 100 µg l–1 Cu. B. neritina and W. subtorquata colonies exhibited reduced post-metamorphic growth in 50 µg l–1 Cu compared to controls, with no growth observed in 100 µg l–1 Cu. Growth for S. errata and T. occidentalis was higher at 0 µg l–1 than 10 µg l–1 Cu. Post-exposure growth of surviving colonies was assessed by transplanting colonies to the field. W. subtorquata colonies exposed to 50 µg l–1 Cu were the only colonies to show decreased survival and growth post Cu-exposure. Overall, B. neritina and W. subtorquata showed the greatest tolerance to Cu. These findings have important implications for the management, control and assessment of invasion potential of these invasive marine hull-fouling species. KEY WORDS: Cu · Attachment · Post-metamorphic survival · Post-metamorphic growth · Antifouling paint · Tolerance · Introduced species · Hull fouling Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 311. Online publication date: April 13, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Dependence of radiochromic film response kinetics on fractionated doses

Because the rate and magnitude of the post-exposure growth of the MD-55 radiochromic film (RCF) dosimeter response depends significantly on total dose, we have investigated the influence of fractionation and protracted dose delivery on optical density (OD) as a function of total dose and the exposure-to-densitometry time interval for a 633-nm scanning laser densitometer. Both measurements and models demonstrate that fractionation induces transient OD over responses, which can be as large as 20%, but rapidly dissipate within 24 h. However, the superposition model predicts 2–5% over responses that persist as long as 700 h.

Effects of a strong static magnetic field on bacteriumShewanella oneidensis: An assessment by using whole genome microarray

The effect of a strong static 14.1 T magnetic field on log phase cells of bacterial strain Shewanella oneidensis MR-1 was evaluated by using whole genome microarray of this bacterium. Although differences were not observed between the treatment and control by measuring the optical density (OD), colony forming unit (CFU), as well as post-exposure growth of cells, transcriptional expression levels of 65 genes were altered according to our microarray data. Among these genes, 21 were upregulated while other 44 were downregulated, compared with control.

Diffusional enhancement of holograms: phenanthrenequinone in polycarbonate

As a further development of the manufacture of holographic gratings by the diffusion of phenanthrenequinone in polymer glass, the traditionally employed poly(methyl methacrylate) is replaced by poly(bisphenol-A-carbonate). The post-exposure growth and decay of the gratings in the two materials are compared at different spatial periods and temperatures. The medium with polycarbonate demonstrates a fortunate combination of significantly improved stability of the gratings and their faster development. Our results indicate that the polycarbonate materials promise to be suitable media for holographic optical elements and data storage.

Acute Toxicity Testing with Juvenile White Sturgeon (Acipenser transmontanus)

Abstract The primary goal of this study was to investigate the possibility of using early life stages of white sturgeon (Acipenser transmontanus) (eggs, larvae and fry) as a species relevant to the Fraser River, B.C., for the acute and sublethal toxico-logical testing of forest industry effluents. Here we report the first successful acute toxicity tests for 8-day-old larvae and 42-day-old fry exposed to several chemicals known to be released into the Fraser River (i.e., 6 monochlorovanillin [6 MVAN], 4,5 dichloroguaiacol [4,5 DCG], 4,5 dichlorocatechol [4,5 DCAT], pentachlorophenol [PCP], and didecyldimethylammonium chloride [DDAC]). In most cases, white sturgeon fry were at the lower end of the range for acute toxicity values for chlorinated phenolic compounds, when compared with other juvenile fish species, and they were extremely sensitive to DDAC. The larval stage was usually more sensitive than the fry stage. Acute toxicity tests with fertilized eggs were unsuccessful. A postexposure growth study was inconclusive because neither control nor toxicant-exposed larvae and fry withstood the additional handling used for measuring body mass. At 62-days-old, fry were more tolerant of handling. This allowed measurement of their swimming performance. Although we have concerns about the reliability of using larvae for acute toxicity testing at this time, 60-day-old white sturgeon fry would appear to be both a sensitive and relevant species for assessing environmental impacts relevant to the Fraser River.

Proliferation of human tumour cells after high-energy pulsed ultrasound (HEPUS) treatment

Summary. The potential anti-proliferative effect of high-energy pulsed ultrasound (HEPUS) treatment on human pancreatic (PANC-1), hepatic (SK-HEP-1) and renal (CAKI-1) tumour cells was investigated in vitro. Sonication was carried out using an experimental piezoelectric burst-signal transducer, producing bipolar oscillations with a high negative pressure amplitude. In all three cell lines tested, HEPUS-application resulted in a significant reduction (P<0.05) of vital cells. After 100 pulses 35%, 20% and 41% viable pancreatic, hepatic and renal tumour cells were detected by means of the Trypan Blue Dye exclusion test, whereas after 1000 pulses only 1.3%, 1% and 0.5% were found. A post-exposure growth delay of surviving cells, compared to control cells and cells treated with 100 pulses, was only seen in case of the CAKI-1 cell line exposed to 1000 pulses.

Intermittent exposure to aquatic pollutants: assessment, toxicity and sublethal responses in fish and invertebrates

Aquatic animals are often exposed to intermittent, variable poison concentrations during pollution incidents. However, current understanding of ecotoxicology has evolved primarily from continuous exposure studies. This review summarises the relatively dispersed toxicity literature on intermittent exposures. Methodologies used in existing continuous exposure toxicity tests may be adapted to intermittent regimes provided the exposure profile is known and “poison concentration” is defined to give toxicologically relevant lethality estimate. Such tests rely on assuming that continuous and intermittent exposures of equivalent dose have the same toxicity. This assumption is untrue for some chemicals. The toxicity of intermittent events may be assessed by correlating mortality with poison accumulation, biochemical, haematological or physiological response syndromes. Such bioassays can be performed without knowledge of the exposure profile, and are often sufficiently rapid to record short pollution events. Intermittent and continuous exposures of equivalent dose may not have the same toxicities. Intermittent exposures are less toxic than continuous events, but only when peak concentrations of pollutant are the same in each regime. Exceptionally, sulphuric acid, acid/Al and ammonia are much more toxic to fish when administered intermittently. Variations in intermittent exposure frequency or duration do not produce proportional changes in lethality, since apparently large changes in exposure dose may not significantly alter toxicity. The short-lived nature of intermittent exposures suggests that equilibriums in poison concentrations between the external environment and the body compartments of the test species are not achieved. The overall accumulation response depends particularly on the duration of peak concentrations and any “recovery periods” between multiple episodes relative to poison uptake and depuration rates respectively. Transient biochemical and physiological disturbances occur during intermittent exposures. Latent effects include reduced post-exposure growth and reproductive failure in the F 1 generation, or increased deformities in the F 2 generation of fish.

Acute toxicity of permethrin to four size classes of red swamp crayfish (Procambarus clarkii) and observations of post-exposure effects

The mean static acute 96-h LC50 of permethrin [(3-phenoxybenzyl (+) cis, trans, 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylate)] to red swamp crayfish (Procambarus clarkii) 8-12 mm (0.017 g), 25-35 mm (0.64 g), 45-55 mm (2.45 g), and 65-75 mm total length (8.98 g) was 0.44, 0.85, 1.30, and 0.81 micrograms/L, respectively. Permethrin toxicity did not differ among immature or mature male and female P. clarkii. Crayfish surviving permethrin exposures exhibited no differences in post-exposure growth, survival, onset of sexual maturity, or the reproduction of viable young when compared to non-exposed controls. Teratogenesis was not observed in third-instar crayfish produced from permethrin-exposed parents.