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- Beal, Jacob, et al.
(author)
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Robust estimation of bacterial cell count from optical density
- 2020
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In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)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.
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- Breugelmans, T., et al.
(author)
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In-Depth Study of Transmembrane Mucins in Association with Intestinal Barrier Dysfunction During the Course of T Cell Transfer and DSS-Induced Colitis
- 2020
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In: Journal of Crohns & Colitis. - : Oxford University Press (OUP). - 1873-9946. ; 14:7, s. 974-994
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Journal article (peer-reviewed)abstract
- Background and Aims: There is evidence for a disturbed intestinal barrier function in inflammatory bowel diseases [IBD] but the underlying mechanisms are unclear. Because mucins represent the major components of the mucus barrier and disturbed mucin expression is reported in the colon of IBD patients, we studied the association between mucin expression, inflammation and intestinal permeability in experimental colitis. Methods: We quantified 4-kDa FITC-dextran intestinal permeability and the expression of cytokines, mucins, junctional and polarity proteins at dedicated time points in the adoptive T cell transfer and dextran sodium sulfate [DSS]-induced colitis models. Mucin expression was also validated in biopsies from IBD patients. Results: In both animal models, the course of colitis was associated with increased interleukin-1 beta [IL-1 beta] and tumour necrosis factor-alpha [TNF-alpha] expression and increased Muc1 and Muc13 expression. In the T cell transfer model, a gradually increasing Muc1 expression coincided with gradually increasing 4-kDa FITC-dextran intestinal permeability and correlated with enhanced IL-1 beta expression. In the DSS model, Muc13 expression coincided with rapidly increased 4-kDa FITC-dextran intestinal permeability and correlated withTNF-alpha and Muc1 overexpression. Moreover, a significant association was observed between Muc1, Cldn1, Ocln, Par3 and aPKC zeta expression in the T cell transfer model and between Muc13, Cldn1, Jam2, Tjp2, aPkc zeta, Crb3 and Scrib expression in the DSS model. Additionally, MUC1 and MUC13 expression was upregulated in inflamed mucosa of IBD patients. Conclusions: Aberrantly expressed MUC1 and MUC13 might be involved in intestinal barrier dysfunction upon inflammation by affecting junctional and cell polarity proteins, indicating their potential as therapeutic targets in IBD.
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- de Smet, P., et al.
(author)
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Gender and regional differences in perceived job stress across Europe
- 2005
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In: Eur J Public Health. - : Oxford University Press (OUP). - 1101-1262 .- 1464-360X. ; 15:5, s. 536-45
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Journal article (peer-reviewed)abstract
- BACKGROUND: Over the last 20 years stress at work has been found to be predictive of several conditions such as coronary heart disease, high blood pressure and non-specific sick leave. The Karasek demand/control/strain concept has been the most widely used in prospective epidemiological studies. OBJECTIVES: To describe distribution in Karasek's demand/control (DC) dimensions as well as prevalence of strain in samples from different parts of Europe grouped into three regions (South, Middle, Sweden), adjusting for occupation. To describe gender differences in Karasek's DC dimensions along with strain prevalence and assess the regional stability of those differences in different occupational groups. DESIGN: The Job stress, Absenteeism and Coronary heart disease in Europe (JACE) study, a Concerted Action (Biomed I) of the European Union, is a multicentre prospective cohort epidemiological study: 38,019 subjects at work aged 35-59 years were surveyed at baseline. Standardised techniques were used for occupation coding (International Standardised Classification of Occupations) and for the DC model (Karasek scale): five items for the psychological demand and nine items for the control or decision latitude dimensions, respectively. RESULTS: A total of 34,972 subjects had a complete data set. There were important regional differences in the Karasek scales and in prevalence of strain even after adjustment for occupational class. Mean demand and control were higher in the Swedish centres when compared to two centres in Milano and Barcelona (Southern region) and values observed in four centres (Ghent, Brussels, Lille and Hoofddorp) in Middle Europe were closer to those observed in the Southern cities than to those obtained in the Swedish cities. Clerks (ISCO 4) and, more specifically, office clerks (ISCO 41) exhibited the smallest regional variation. In a multivariate model, the factor 'region' explained a small fraction of total variance. In the two Southern centres as well as in the four Middle European centres, men perceived marginally less job-demand as compared to women whereas the reverse was observed in the two Swedish centres. Differences were larger for control: men appeared to perceive more control at work than did women. In a multivariate model, gender explained a small fraction whereas occupational level explained a large fraction of the variance. CONCLUSIONS: In this standardised multicentre European study Karasek's DC model showed large gender and occupational differences whereas geographic region explained a small fraction of the total DC variance, notwithstanding large differences in labour market and working conditions as pointed out by the European Commission as recently as 2000.
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- Swarup, Kamal, et al.
(author)
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The auxin influx carrier LAX3 promotes lateral root emergence
- 2008
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In: Nature Cell Biology. - : Nature Publishing Group. - 1465-7392 .- 1476-4679. ; 10:8, s. 946-954
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Journal article (peer-reviewed)abstract
- Lateral roots originate deep within the parental root from a small number of founder cells at the periphery of vascular tissues and must emerge through intervening layers of tissues. We describe how the hormone auxin, which originates from the developing lateral root, acts as a local inductive signal which re-programmes adjacent cells. Auxin induces the expression of a previously uncharacterized auxin influx carrier LAX3 in cortical and epidermal cells directly overlaying new primordia. Increased LAX3 activity reinforces the auxin-dependent induction of a selection of cell-wall-remodelling enzymes, which are likely to promote cell separation in advance of developing lateral root primordia.
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