| 1. |
- Beal, Jacob, et al.
(författare)
-
Robust estimation of bacterial cell count from optical density
- 2020
-
Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
|
|
| 2. |
- Ferwerda, Bart, et al.
(författare)
-
Functional and genetic evidence that the Mal/TIRAP allele variant 180L has been selected by providing protection against septic shock.
- 2009
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:25, s. 10272-10277
-
Tidskriftsartikel (refereegranskat)abstract
- Adequate responses by our innate immune system toward invading pathogens were of vital importance for surviving infections, especially before the antibiotic era. Recently, a polymorphism in Mal (Ser180Leu, TIRAP rs8177374), an important adaptor protein downstream of the Toll-like receptor (TLR) 2 and 4 pathways, has been described to provide protection against a broad range of infectious pathogens. We assessed the functional effects of this polymorphism in human experimental endotoxemia, and we demonstrate that individuals bearing the TIRAP 180L allele display an increased, innate immune response to TLR4 and TLR2 ligands, but not to TLR9 stimulation. This phenotype has been related to an increased resistance to infection. However, an overshoot in the release of proinflammatory cytokines by TIRAP 180L homozygous individuals suggests a scenario of balanced evolution. We have also investigated the worldwide distribution of the Ser180Leu polymorphism in 14 populations around the globe to correlate the genetic makeup of TIRAP with the local infectious pressures. Based on the immunological, clinical, and genetic data, we propose that this mutation might have been selected in West Eurasia during the early settlement of this region after the out-of-Africa migration of modern Homo sapiens. This combination of functional and genetic data provides unique insights to our understanding of the pathogenesis of sepsis.
|
|
| 3. |
- Heikkinen, Päivi, et al.
(författare)
-
A 28-day toxicity study with highly purified PCB 180 in Sprague–Dawley rats
- 2008
-
Ingår i: Toxicology Letters. - : Elsevier. ; , s. 205-
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- PCB 180 is a persistent and accumulative heptachlorinated non-dioxin-like polychlorinated biphenyl (NDL-PCB) abundantly present in food and the environment. Risk characterisation of NDL-PCBs has been confounded by the presence of highly potent dioxin-like (DL) impurities. We used therefore highly purified PCB 180 (DL impurities 2.7 ng TEqWHO/g PCB 180) for the 28-day toxicity study in adult rats. Groups of 5 males and 5 females were given total doses of 3, 10, 30, 100, 300, 1000 or 1700 mg/kg PCB 180 by gavage. Total dose was divided into 6 daily loading doses and 3 weekly maintenance doses. Bodyweight development was retarded at 1700 mg/kg during loading dosing, but recovered by the end of the study. Hepatic effects are reported separately (Roos et al., ibid.). Thyroid weight was increased in males. Plasma free T4 was dose-dependently decreased (maximally by 69% in males and 50% in females) in association with thyroid follicle depletion, but T3 was not affected. Increased thyroid follicle cell vacuolization is suggestive of thyroid activation. In males, vacuolization and extracellular deposits were observed in the frontal part of pituitary. Activation of adrenal cortex is demonstrated by vacuolization and hypertrophy observed in cells of zona fasciculata of the adrenal cortex. Erythrocyte parameters (red blood cell count, haematocrit, haemoglobin) were dose-dependently decreased in both genders. The results demonstrate a distinct toxicological profile of PCB 180 with some similarities with that of DL compounds, but clearly lower potency.Acknowledgement: Funded by the European Commission (ATHON, FOOD-CT-2005-022923
|
|
| 4. |
- Lilienthal, Hellmuth, et al.
(författare)
-
Auditory effects of developmental exposure to purity-controlled Polychlorinated Biphenyls (PCB52 and PCB180) in rats
- 2011
-
Ingår i: Toxicological Sciences. - : Oxford Journals. - 1096-6080 .- 1096-0929. ; 122:1, s. 100-111
-
Tidskriftsartikel (refereegranskat)abstract
- Polychlorinated biphenyls (PCBs) are still present in the environment, with ongoing exposure in humans, including babies nursed by their mothers. Whereas toxicity of dioxin-like PCBs is well described, less systematic knowledge is available for non-dioxin-like PCBs (NDL-PCBs) which do not act via the Ah receptor. This study compared effects of developmental exposure to two ultrapure NDL-PCB congeners (PCB52 and PCB180) on auditory function in rats, using the brainstem auditory evoked potential (BAEP). Pregnant rats received repeated oral doses of PCB52 (total dose - 0, 30, 100, 300, 1000, or 3000 mg/kg body weight) or of PCB180 (total dose - 0, 10, 30, 100, 300, or 1000 mg/kg). BAEPs were recorded in adult male and female offspring after stimulation with clicks or pure tones in the frequency range from 0.5 kHz to 16 kHz. Significant elevation of BAEP thresholds were detected in the low-frequency range after developmental exposure to PCB52. Calculation of benchmark doses revealed lowest values in the frequency range of 0.5 - 2 kHz. Effects were more pronounced in male compared to female offspring. Latencies of waves II and IV were prolonged in exposed males, while only wave IV was affected in females. PCB180 increased thresholds only at few conditions and only in female offspring. These results confirm that developmental exposure to ultrapure NDL-PCBs affects auditory function, but different congeners exhibit differences in potencies.
|
|
| 5. |
- Lilienthal, Hellmuth, et al.
(författare)
-
Dopamine-dependent behavior in adult rats after perinatal exposure to purity-controlled polychlorinated biphenyl congeners (PCB52 and PCB180)
- 2014
-
Ingår i: Toxicology Letters. - : Elsevier. - 0378-4274 .- 1879-3169. ; 224:1, s. 32-39
-
Tidskriftsartikel (refereegranskat)abstract
- Since knowledge about toxic effects of non-dioxinlike (NDL) PCBs is fragmentary, regulatory panels have concluded that risk assessment of these congeners is hampered or impossible. As the dopaminergic system is one of the main targets in PCB-related neurotoxic effects after developmental exposure, we selected catalepsy induced by the dopamine receptor blocker haloperidol to characterize effects of the NDL congeners PCB52 and PCB180 in adult offspring from exposed rat dams. Rat dams were treated with PCB congeners by gavage using six dose levels (total doses: PCB52 - 0, 30, 100, 300, 1000 or 3000 mg/kg body wt.; PCB180 - 0, 10, 30, 100, 300, or 1000 mg/kg body wt.) to allow benchmark dose analysis of the results. Testing of adult offspring (starting at 180 days of age) for catalepsy induced by injection with haloperidol revealed slightly prolonged latencies to movement onset in female offspring exposed to PCB52. Exposure to PCB180 resulted in more pronounced effects, with generally reduced latencies in male offspring. These results indicate reduced dopaminergic activity after PCB52 exposure, whereas the outcome for PCB180 may be related to increased extracellular dopamine as reported in the literature. Benchmark dose analyses revealed that both PCB congeners exerted effects mainly at moderate exposure levels. Together, these results underline the importance of effects on the dopaminergic system as indicated by studies in human females after occupational PCB exposure.
|
|
| 6. |
- Roos, Robert, et al.
(författare)
-
Hepatic effects of a highly purified 2,2',3,4,4',5,5'-heptachlorbiphenyl (PCB 180) in male and female rats.
- 2011
-
Ingår i: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 284:1-3, s. 42-53
-
Tidskriftsartikel (refereegranskat)abstract
- PCB 180 (2,2',3,4,4',5,5'-heptachlorobiphenyl) is a persistent and accumulating polychlorinated biphenyl abundantly present in food and the environment. In this study, we used highly purified PCB 180 (dioxinlike impurities: 2.7 ng TEQ(WHO)/g PCB 180) in a 28-day toxicity study in young adult Sprague-Dawley rats. Male and female rats were given total doses of 3, 10, 30, 100, 300, 1000 or 1700 mg/kg b.w. PCB 180 by gavage. Increased liver weights were observed at ≥ 300 mg/kg b.w. in males and females. No increases in serum ALT or ALP activities were found. A significant increase in liver pentoxyresorufin O-dealkylase (PROD) activity was found in males at ≥ 10 mg/kg b.w. and in females at ≥ 30 mg/kg b.w. In both genders, a significant induction of hepatic 7-ethoxyresorufin O-deethylase (EROD) activity was also observed in males at ≥ 10 mg/kg b.w. and in females at ≥ 300 mg/kg b.w. Western blotting showed that mainly cytochromes P450 (CYPs) 2B1/2 and 3A1 were induced while slight effects were seen on CYP1A1, CYP1A2 and CYP1B1. However, no induction of CYP1A1, 1A2 and 1B1 was found on the mRNA level, except for a slight effect in females at 1000 mg/kg b.w. Furthermore, hepatic UDP-glucuronosyltransferases (UGTs) 1A1 and 1A6 were markedly induced in males and slightly induced in females. The hepatic concentrations of apolar retinoids were decreased in males at ≥ 30 mg/kg b.w. and in females at ≥ 300 mg/kg b.w. Taken together our findings show that pure PCB 180 leads to hepatic changes in a dose range which did not cause CYP1A1 induction but causes centrilobular liver hypertrophy, affects drug-metabolizing enzymes involved in the metabolism of exogenous and endogenous substrates and leads to changes in liver retinoid levels. A benchmark dose (BMD) approach is presented in order to model lowest effective dose levels for these effects. Comparison of PCB 180 liver level related to BMDL₅ for hepatic hypertrophy in rats with human data on 'total' hepatic PCB levels in individuals without history of specific exposure suggests a relatively small margin of tissue burden in the range of 37-fold. Our results show that the highly pure non dioxin-like PCB 180 exerted strong effects different to dioxin-like compounds and that the low TEQ contamination allowed a characterization of the PCB as non-dioxinlike.
|
|
| 7. |
- Viluksela, Matti, et al.
(författare)
-
Toxicological profile of ultrapure 2,2',3,4,4',5,5'-heptachlorbiphenyl (PCB 180) in adult rats.
- 2014
-
Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 9:8, s. e104639-
-
Tidskriftsartikel (refereegranskat)abstract
- PCB 180 is a persistent non-dioxin-like polychlorinated biphenyl (NDL-PCB) abundantly present in food and the environment. Risk characterization of NDL-PCBs is confounded by the presence of highly potent dioxin-like impurities. We used ultrapure PCB 180 to characterize its toxicity profile in a 28-day repeat dose toxicity study in young adult rats extended to cover endocrine and behavioral effects. Using a loading dose/maintenance dose regimen, groups of 5 males and 5 females were given total doses of 0, 3, 10, 30, 100, 300, 1000 or 1700 mg PCB 180/kg body weight by gavage. Dose-responses were analyzed using benchmark dose modeling based on dose and adipose tissue PCB concentrations. Body weight gain was retarded at 1700 mg/kg during loading dosing, but recovered thereafter. The most sensitive endpoint of toxicity that was used for risk characterization was altered open field behavior in females; i.e. increased activity and distance moved in the inner zone of an open field suggesting altered emotional responses to unfamiliar environment and impaired behavioral inhibition. Other dose-dependent changes included decreased serum thyroid hormones with associated histopathological changes, altered tissue retinoid levels, decreased hematocrit and hemoglobin, decreased follicle stimulating hormone and luteinizing hormone levels in males and increased expression of DNA damage markers in liver of females. Dose-dependent hypertrophy of zona fasciculata cells was observed in adrenals suggesting activation of cortex. There were gender differences in sensitivity and toxicity profiles were partly different in males and females. PCB 180 adipose tissue concentrations were clearly above the general human population levels, but close to the levels in highly exposed populations. The results demonstrate a distinct toxicological profile of PCB 180 with lack of dioxin-like properties required for assignment of WHO toxic equivalency factor. However, PCB 180 shares several toxicological targets with dioxin-like compounds emphasizing the potential for interactions.
|
|
