| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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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.
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| 2. |
- Järemo, Petter, et al.
(författare)
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Alzheimer's disease and granulocyte density diversity
- 2013
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Ingår i: European Journal of Clinical Investigation. - : John Wiley & Sons. - 0014-2972 .- 1365-2362. ; 43:6, s. 545-548
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:The current study investigates circulating eosinophils and neutrophils in Alzheimer's (AD) type dementia with respect to density (kg/L). The existence of β-amyloid plaques in the brain is a feature of AD. Sporadic scientific reports indicate that the disease affects circulating neutrophils. In contrast, numerous publications investigate inflammatory reactions in AD brains. Locally, the plaques evoke a substantial inflammatory response involving activated microglia and astrocytes.METHODS:Subjects with probable AD (n = 39) were included and compared with elderly individuals (n = 22) lacking apparent memory problems. We sampled 10 mL venous blood in citrate. Granulocytes were separated according to density in linear Percoll™ gradients. Subsequently, the gradients were divided into density subfractions (n = 16). In every fraction, determination of eosinophil and neutrophil counts was carried out.RESULTS:AD sufferers displayed less granulocytes in fractions nos. 13-15 containing light cells. For these fractions, the P-values proved to be (P < 0·001; not significant; P = 0·03) and (P = 0·01; P = 0·01; not significant), for eosinophils and neutrophils, respectively.CONCLUSIONS:The present work describes that less circulating light granulocytes are a feature of AD demented individuals. It is to hypothesize that it is a sign of impaired granulocyte turnover and cell damage. It is concluded that AD affects inflammatory cells in the periphery and that the behaviour of granulocytes in dementia is worthwhile further studies.
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| 3. |
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| 4. |
- Järemo, Petter, et al.
(författare)
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Low-density platelet populations demonstrate low in vivo activity in sporadic Alzheimer disease
- 2012
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Ingår i: Platelets. - London : Informa Healthcare. - 0953-7104 .- 1369-1635. ; 23:2, s. 116-120
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Tidskriftsartikel (refereegranskat)abstract
- Platelets contain a substantial quantity of amyloid-precursor protein (APP) and β-amyloid. However, despite the large importance of APP and β-amyloid to dementia, little is known about platelets in sporadic Alzheimer dementia (AD). Furthermore, platelet heterogeneity influences human pathology and has been described to affect the progression of AD. This study investigated AD platelets with respect to density diversity and in vivo activity associated with density sub-fractions. We included 39 AD patients and used, as controls, 22 elderly individuals without apparent memory disorder. A continuous Percoll™ gradient covering the density span 1.04–1.09 kg/l provided the basis to divide platelets of whole blood into density fractions (n = 16). All platelet populations were evaluated accordingly. Platelet counts were determined electronically. A flow-cytometer was put to use to measure surface-bound fibrinogen as a measure of platelet in vivo activity. Samples obtained from patients diagnosed with sporadic AD contained platelets (fractions numbers 4–16) that circulated with significantly less surface-bound fibrinogen, i.e., their platelet activation in vivo was reduced, compared with controls. In particular, highly significant differences (p < 0.001) were obtained for the six less dense platelet populations (fractions numbers 11–16) when comparing sporadic AD with controls. In contrast, the densest AD platelets in fractions numbers 1–3 did not differ significantly from control cells with respect to in vivo platelet-bound fibrinogen. It is concluded that sporadic AD is characterized by lower density platelet populations that, while circulating, exhibited reduced activation. The clinical significance of this finding is unclear but these results suggest the importance of platelet heterogeneity in dementia as a topic for further investigation.
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| 5. |
- Järemo, Petter, et al.
(författare)
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P-selectin paradox and dementia of the Alzheimer type: Circulating P-selectin is increased but platelet-bound P-selectin after agonist provocation is compromised
- 2013
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - : Informa Healthcare. - 0036-5513 .- 1502-7686. ; 73:2, s. 170-174
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Knowledge concerning the neurobiological importance of platelets in Alzheimers disease (AD) is sparse. P-selectin, which is located together with beta-amyloid precursor proteins in platelet alpha-granules, is also found in endothelial cells. Upon activation, P-selectin is relocated to cell surfaces where it acts as a receptor. Subsequently, the protein is cleaved from the membrane, to then be circulated. We investigated P-selectin behavior in AD dementia. Methods. We recruited 23 persons diagnosed moderate AD and 17 healthy elders without obvious memory problems. Circulating P-selectin was analyzed using an ELISA technique and flow cytometry was used to measure surface-bound P-selectin. The latter measure was carried out without provocation (platelet activity) and after in vitro agonist stimulation (platelet reactivity). A thrombin-receptor activating peptide (TRAP-6) (74 mu mol/L)) was used as a platelet agonist. Results. Soluble P-selectin was augmented in AD (p = 0.019) but platelet membrane-attached P-selectin did not differ from controls. AD diagnosis was associated with less surface-bound P-selectin after provocation. Significant results were obtained when 74 mu mol/L TRAP-6 was used as a platelet agonist (p = 0.0008). Conclusion. This study describes apparently paradoxical P-selectin reactions in moderate AD. While soluble P-selectin was higher in the disease group, membrane-attached P-selectin without agonist stimulation was no different between the disease and control groups. In contrast, AD was linked to lower platelet reactivity. The current findings encourage further research into this P-selectin paradox and its relevance for AD and, perhaps, other types of dementia as well.
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