| 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. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- He, ZY, et al.
(författare)
-
None of the integrins known to be present on the mouse egg or to be ADAM receptors are essential for sperm-egg binding and fusion
- 2003
-
Ingår i: Developmental Biology. - 1095-564X. ; 254:2, s. 226-237
-
Tidskriftsartikel (refereegranskat)abstract
- Antibody inhibition and alpha6beta1 ligand binding experiments indicate that the egg integrin alpha6beta1 functions as a receptor for sperm during gamete fusion; yet, eggs null for the alpha6 integrin exhibit normal fertilization. Alternative integrins may be involved in sperm-egg binding and fusion and could compensate for the absence of alpha6beta1. Various beta1 integrins and alphav integrins are present on mouse eggs. Some of these integrins are also reported to be receptors for ADAMs, which are expressed on sperm. Using alpha3 integrin null eggs, we found that the alpha3beta1 integrin was not essential for sperm-egg binding and fusion. Oocyte-specific, beta1 integrin conditional knockout mice allowed us to obtain mature eggs lacking all beta1 integrins. We found that the beta1 integrin null eggs were fully functional in fertilization both in vivo and in vitro. Furthermore, neither anti-mouse beta3 integrin function-blocking monoclonal antibody (mAb) nor alphav integrin function-blocking mAb inhibited sperm binding to or fusion with beta1 integrin null eggs. Thus, function of beta3 or alphav integrins does not seem to be involved in compensating for the absence of beta1 integrins. These results indicate that none of the integrins known to be present on mouse eggs or to be ADAM receptors are essential for sperm-egg binding/fusion, and thus, egg integrins may not play the role in gamete fusion previously attributed to them.
|
|
| 8. |
- Hedlund, Petter, et al.
(författare)
-
Erectile dysfunction in cyclic CMP-dependent kinase I-deficient mice
- 2000
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences; 1999. - 0027-8424 .- 1091-6490. ; 97:5, s. 2349-2354
-
Tidskriftsartikel (refereegranskat)abstract
- The generation of nitric oxide (NO) in penile erectile tissue and the subsequent elevation of cyclic GMP (cGMP) levels are important for normal penile erection. Current treatments of erectile dysfunction elevate either cGMP levels by blocking cGMP degrading phosphodiesterase 5 or cyclic AMP (cAMP) levels by intrapenile injection of prostaglandin E1. The molecular target or targets of cGMP in erectile tissue and the role of cAMP for normal penile erection are not known. Herein, we report that mice lacking cGMP-dependent kinase I (cGKI) have a very low ability to reproduce and that their corpora cavernosa fail to relax on activation of the NO/cGMP signaling cascade. Elevation of cAMP by forskolin, however, induces similar relaxation in normal and cGKI-null corpus cavernosum. In addition, sperm derived from cGKI-null mice is normal, can undergo acrosomal reactions, and can efficiently fertilize eggs. Altogether, these data identify cGKI as the downstream target of cGMP in erectile tissue and provide evidence that cAMP signaling cannot compensate for the absence of the cGMP/cGKI signaling cascade in vivo.Penile erection is produced by an increased blood flow to the corpus cavernosum (CC), made possible by opening of penile resistance vessels (helicine arteries), relaxation of the CC cells, and occlusion of the venous outflow (1). The erectile response in several animal models depends on nitric oxide (NO), produced by nerves as well as vascular endothelium (1, 2–4). NO activates soluble guanylate cyclase, which leads to the production of cyclic GMP (cGMP). cGMP signals via three different receptors in eukaryotic cells, including ion channels, phosphodiesterases, and protein kinases (5). At present, however, the molecular targets that are activated by cGMP and finally execute the relaxation of penile smooth muscle are not known. In addition, two different cGMP-dependent protein kinases (cGKI and cGKII) have been identified in mammals (6, 7). cGKII is expressed in the small intestine, brain, and cartilage (8–10), whereas high levels of cGKI are found in vascular and intestinal smooth muscle, platelets, Purkinje cells of the cerebellum, and CC cells (11, 12). Inactivation of cGKI in mice abolished both NO/cGMP-dependent relaxation of vascular and intestinal smooth muscle and inhibition of platelet aggregation, causing hypertension, intestinal dysmotility, and abnormal hemostasis (13). In the present study, we investigated the function of cGKI in erectile tissue and the capability of cGKI-deficient mice to reproduce. Furthermore, we analyzed whether a cross-talk exists between the cGMP and cyclic AMP (cAMP) signaling cascades in smooth muscle (5, 14), i.e., whether cAMP can cause relaxation via cGKI.
|
|
| 9. |
- Herzog, C, et al.
(författare)
-
Dystroglycan in skin and cutaneous cells: beta-subunit is shed from the cell surface
- 2004
-
Ingår i: Journal of Investigative Dermatology. - 1523-1747. ; 122:6, s. 1372-1380
-
Tidskriftsartikel (refereegranskat)abstract
- In skin, hemidesmosomal protein complexes attach the epidermis to the dermis and are critical for stable connection of the basal epithelial cell cytoskeleton with the basement membrane (BM). In muscle, a similar supramolecular aggregate, the dystrophin glycoprotein complex links the inside of muscle cells with the BM. A component of the muscle complex, dystroglycan (DG), also occurs in epithelia. In this study, we characterized the expression and biochemical properties of authentic and recombinant DG in human skin and cutaneous cells in vitro. We show that DG is present at the epidermal BM zone, and it is produced by both keratinocytes and fibroblasts in vitro. The biosynthetic precursor is efficiently processed to the alpha- and beta-DG subunits; and, in addition, a distinct extracellular segment of the transmembranous beta-subunit is shed from the cell surface by metalloproteinases. Shedding of the beta-subunit releases the alpha-subunit from the DG complex on the cell surface into the extracellular space. The shedding is enhanced by IL-1beta and phorbol esters, and inhibited by metalloproteinase inhibitors. Deficiency of perlecan, a major ligand of alpha-DG, enhanced shedding suggesting that lack of a binding partner destabilizes the epithelial DG complex and makes it accessible to proteolytic processing.
|
|
| 10. |
|
|
