Radiation dose reduction by adjusting bolus tracking parameters in a 320-detector row scanner.

BACKGROUND: The importance of bolus tracking (BT) regarding total effective radiation dose (ERD) in the era of advanced coronary computed tomography angiography (CTA) has been ignored. We aimed to investigate whether adjusting BT parameters reduces ERD. METHODS: Adults consecutively referred to CTA (n = 289) in a 320 detector-row scanner were distributed into four BT protocols according to delay time and time between intermittent scans, as follows: A (n = 70, delay 10s, intermittent scans 1s); B (n = 79, delay 10s, intermittent scans 2s); C (n = 68, delay 15s, intermittent scans 1s); and D (n = 72, delay 15s, intermittent scans 2s). Image quality was assessed. RESULTS: The overall ERD in BT and AP were 0.32 ±â€¯0.14 mSv and 6.06 ±â€¯0.66 mSv, respectively. ERD in BT was different among protocols (A:0.44 ±â€¯0.14 mSv; B:0.32 ±â€¯0.10 mSv; C:0.28 ±â€¯0.14 mSv; D:0.23 ±â€¯0.09 mSv; p < 0.001), with no loss in image quality. Adjusted for potential confounders (heart rate, tube current and acquisition window), protocol D provided the highest reduction in total ERD (ß = -0.33, p = 0.004). CONCLUSION: Delaying initiation of BT images (and acquiring them less frequently) reduces radiation dose and does not impair image quality.

Assessment of biomarkers for contaminants of emerging concern on aquatic organisms downstream of a municipal wastewater discharge.

Contaminants of emerging concern (CECs), including pharmaceuticals, personal care products and estrogens, are detected in wastewater treatment plant (WWTP) discharges. However, analytical monitoring of wastewater and surface water does not indicate whether CECs are affecting the organisms downstream. In this study, fathead minnows (Pimephales promelas) and freshwater mussels Pyganodon grandis Say, 1829 (synonym: Anodonta grandis Say, 1829) were caged for 4 weeks in the North Saskatchewan River, upstream and downstream of the discharge from the WWTP that serves the Edmonton, AB, Canada. Passive samplers deployed indicated that concentrations of pharmaceuticals, personal care products, an estrogen (estrone) and an androgen (androstenedione) were elevated at sites downstream of the WWTP discharge. Several biomarkers of exposure were significantly altered in the tissues of caged fathead minnows and freshwater mussels relative to the upstream reference sites. Biomarkers altered in fish included induction of CYP3A metabolism, an increase in vitellogenin (Vtg) gene expression in male minnows, elevated ratios of oxidized to total glutathione (i.e. GSSG/TGSH), and an increase in the activity of antioxidant enzymes (i.e. glutathione reductase, glutathione-S-transferase). In mussels, there were no significant changes in biomarkers of oxidative stress and the levels of Vtg-like proteins were reduced, not elevated, indicating a generalized stress response. Immune function was altered in mussels, as indicated by elevated lysosomal activity per hemocyte in P. grandis caged closest to the wastewater discharge. This immune response may be due to exposure to bacterial pathogens in the wastewater. Multivariate analysis indicated a response to the CECs Carbamazepine (CBZ) and Trimethoprim (TPM). Overall, these data indicate that there is a 1 km zone of impact for aquatic organisms downstream of WWTP discharge. However, multiple stressors in municipal wastewater make measurement and interpretation of impact of CECs difficult since water temperature, conductivity and bacteria are also inducing biomarker responses in both fish and mussels.

Thyroglobulin type-1 domain protease inhibitors exhibit specific expression in the cortical ooplasm of vitellogenic rainbow trout oocytes.

The synthesis, uptake, and processing of yolk proteins remain poorly described aspects of oviparous reproductive development. In this study, we report the identification and characterization of two protease inhibitors in rainbow trout ovary whose expression and distribution are directly associated with yolk protein uptake in vitellogenic oocytes. The first transcript, termed "oocyte protease inhibitor-1" (OPI-1), is predicted to encode a 9.1 kDa, 87 amino acid protein containing a single thyroglobulin type-1 (TY) domain, identifying it as a putative TY domain inhibitor. The second transcript, termed OPI-2, is predicted to encode an 18.3 kDa, 173 amino acid protein with two similar, but not identical, TY domains. Messenger RNA expression of both genes was first detected in ovarian tissues at the onset of vitellogenesis, and persisted throughout the vitellogenic growth phase. We did not detect expression of either gene in previtellogenic ovaries, nor in any somatic tissues examined. Expression of OPI-1 mRNA was significantly reduced in atretic follicles as compared to healthy vitellogenic follicles, suggesting a downregulation of inhibitor expression during oocyte atresia. Western immunoblot analyses of whole yolk from vitellogenic oocytes revealed the presence of two immunoreactive proteins that corresponded to the predicted sizes of OPI-1 and OPI-2. We detected strong crossreactivity of this antiserum with specific vesicles in the cortical ooplasm of vitellogenic oocytes, in regions directly associated with vitellogenin processing. The identification of OPI-1 and OPI-2 provides new evidence for the expression of multiple TY domain protease inhibitors likely involved in the regulation of yolk processing during oocyte growth in salmonids.

Activin and transforming growth factor-beta as local regulators of ovarian steroidogenesis in the goldfish.

This study explores the hypothesis that activin and TGFbeta(1) serve as local regulators of ovarian function in the goldfish. Initial studies demonstrated the presence of TGFbeta in the ovary through the use RT-PCR, which amplified a 225 bp product from early vitellogenic (EVIT) and prematurational full-grown (PFG) follicles. This transcript showed high homology to TGFbeta in other teleosts. Both goldfish recombinant activin B and human recombinant TGFbeta(1) suppressed basal testosterone production by EVIT follicles incubated in vitro. Activin B also inhibited hCG-stimulated testosterone production by EVIT follicles. Our experiments suggest that activin B mediates these effects through actions at sites upstream of cholesterol formation and/or mobilization in the steroidogenic pathway, and through mechanisms that were independent of effects on cAMP formation. In experiments with PFG follicles, TGFbeta(1) decreased basal testosterone production. Activin B did not affect T production by PFG follicles, suggesting that this hormone has differential effects on steroidogenesis in the goldfish ovary depending on the stage of ovarian maturity. In other tests with PFG follicles, TGFbeta(1) and activin B, to a limited extent, inhibited the conversion of 17 alpha-OHP to the maturation-inducing hormone, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one. In conclusion, this study shows that TGF is expressed in the goldfish ovary, and that both activin and TGFbeta affect steroid production, which provides evidence that these members of the TGFbeta superfamily may act as local regulators of ovarian function in a teleost.