Quantitative determination of deoxyribonucleic acid from cells collected on filters

Shear-resistant hydrogels to control permeability of porous tubular scaffolds in vascular tissue engineering

Aiming to perfuse porous tubular scaffolds for vascular tissue engineering (VTE) with controlled flow rate, prevention of leakage through the scaffold lumen is required. A gel coating made of 8% w/v alginate and 6% w/v gelatin functionalized with fibronectin was produced using a custom-made bioreactor-based method. Different volumetric proportions of alginate and gelatin were tested (50/50, 70/30, and 90/10). Gel swelling and stability, and rheological, and uniaxial tensile tests reveal superior resistance to the aggressive biochemical microenvironment, and their ability to withstand physiological deformations (~10%) and wall shear stresses (5-20 dyne/cm²). These are prerequisites to maintain the physiologic phenotypes of vascular smooth muscle cells and endothelial cells (ECs), mimicking blood vessels microenvironment. Gels can induce ECs proliferation and colonization, especially in the presence of fibronectin and higher percentages of gelatin. The custom-designed bioreactor enables the development of reproducible and homogeneous tubular gel coating. The permeability tests show the effectiveness of tubular scaffolds coated with 70/30 alginate/gelatin gel to occlude wadding pores, and therefore prevent leakages. The synthesized double-layered tubular scaffolds coated with alginate/gelatin gel and fibronectin represent both promising substrate for ECs and effective leakproof scaffolds, when subjected to pulsatile perfusion, for VTE applications.

Fluorometric determination of DNA in aquatic microorganisms by use of hoechst 33258

A method for the determination of microbial DNA in aquatic environments by the use of Hoechst 33258 has been developed. With unsophisticated instrumentation and simple extraction procedures, it is possible to detect from 0.05 to 10 mug of DNA in bacterial cultures or natural water samples. The method is specific for DNA; DNase I treatment of extracts of natural microbial populations removed 95 to 100% of the observed fluorescence. DNA content ranged from 165 ng ml for relatively eutrophic Potomac River water to 27 ng ml for coastal Atlantic Ocean water and was correlated to an acridine orange direct count (r = 0.90).

Simplified method for dissolved DNA determination in aquatic environments

A method was developed for the determination of dissolved DNA in aquatic environments. The method is based upon the concentration of dissolved DNA by ethanol precipitation of 0.2-mum-pore-size filtered water. The DNA in concentrated extracts was quantified by the fluorescence of Hoechst 33258-DNA complexes. Fluorescence not attributable to DNA was corrected for by DNase I digestion of the extracts and averaged 25% of the total fluorescence for all samples. The effectiveness of the procedure for concentrating dissolved DNA was demonstrated by the efficient (>90%) recovery of internal standards. Concentrations of dissolved DNA from a variety of marine and freshwater environments ranged from 0.2 to 44 mug/liter, with the highest values being obtained for estuarine and river environments. The method is simple, specific for DNA, and more sensitive than previously described methods for the determination of extracellular DNA.

Intravital fluorescence microscopy of endothelial cells on vascular grafts

The ability to evaluate the extent of initial endothelial cell coverage on a vascular graft subsequent to an endothelial cell seeding technique would be desirable to substantiate the durability of the endothelial cell lining. To this end, we have evaluated the use of intravital fluorescence microscopy to assess human endothelial cell interaction with vascular grafts. Five fluorescent stains, mithramycin, Hoechst 33342, sulfofluorescein diacetate, Nile red, and rhodamine 123 were evaluated for their ability to fluorescently label human endothelial cells. The staining capability of each dye was also evaluated with respect to accuracy in determining seeded cell number and cell spreading. Of the stains evaluated, rhodamine 123 produced the most desirable characteristics. We observed excellent cell visualization after a 30-min incubation. Unlike the other four stains, rhodamine 123 exhibited a bright orange fluorescence emission at a 510-nm excitation wavelength while the underlying dacron or expanded polytetrafluoroethylene demonstrated minimal autofluorescence. Rhodamine 123 also exhibited no inhibitory effect on cell attachment to plastic or subsequent cell growth in culture. Intravital fluorescence microscopy could be easily utilized in the operating room to visualize part or all of an endothelial cell-seeded graft prior to implantation and would permit a quantitative as well as qualitative evaluation of the seeding process. Since intravital fluorescence imaging does not require tissue fixation, the same surface as that evaluated for seeding efficiency can be directly implanted.

Picogram per cell determination of DNA by flow cytofluorometry

Using nuclei isolated from less than 0.2 g tissue or 10(7) cells, a method is presented for the quantitative determination of amounts of DNA per cell at the picogram level. This technique is based on the enhanced fluorescence of 4',6-diamidino-2-phenylindole (DAPI) when it binds to DNA. A rapid, one-step nuclear isolation and DNA staining procedure is used to prepare tissue samples for flow cytometric analysis. Frozen tissues give results comparable to those for fresh tissue. Both chicken and trout erythrocyte nuclei were used as reference standards in the determination of amounts of DNA per diploid cell for several mammals and Amazon molly fish. The consistent values obtained for different tissues from the same organism show the accuracy of this method for DNA measurement.

Fluorometric determination of DNA in epidermis and cultured fibroblasts, using 4'-6-diamidino-2-phenylindole (DAPI)

4'-6-diamidino-phenylindole (DAPI) which is used for the detection of mycoplasmic infections of cell cultures or cytofluorometric investigations proved to be a sensitive agent for the fluorometric assay of alkali extracted DNA in cultured cells and human epidermis. Various experiments to optimize assay conditions led to the following procedure: 1 part of freeze dried tissue (1 mg/ml) and 1 part of 0.2 mol/l NaOH(w/v) were heated at 95 degrees for 40 min. After cooling for 1 h to room temperature, 0.1 ml alkaline extract was mixed with 2.9 ml DAPI-solution (0.2 microgram/ml in McIlvaine buffer containing 1 mmol/l MgCl2). After 10 min in the dark the emitted fluorescence was estimated at 453 nm with an excitation at 360 nm. This assay procedure allowed a detection limit of 25 ng DNA.

Fluorometric quantification of DNA in cells and tissue

The validation of a simple and rapid DNA solubilization procedure is described. Quantitative extraction of intact, polymerized DNA was achieved by cell lysis or tissue homogenization in an ammonium hydroxide-Triton X-100 solution. The solubilization procedure inactivates endogenous DNAase and increases the fluorescence-enhancement activity of the extracted DNA, thereby eliminating the need for enzyme treatment or exposure to high salt solutions. The extracts can be utilized directly in a sensitive fluorescence-enhancement assay with bisbenzimidazole (Hoechst 33258) reagent. Estimates of DNA cell content were unaffected by the number of cells lysed or the volume of lysate employed in the assay. In all cases, the solubilized DNA estimates were linear and parallel to the bovine DNA standard. The optimum range for estimation of DNA in this assay is 5-150 ng. In addition, estimates of DNA obtained with this method and the standard diphenylamine assay were in excellent agreement. This simple, one-step DNA extraction procedure can be utilized in conjunction with Hoechst reagent to obtain quantitative estimates of DNA levels in cell or tissue extracts.

Micropinocytic ingestion of glycosylated albumin by isolated microvessels: possible role in pathogenesis of diabetic microangiopathy

Microvessels isolated from rat epididymal fat exhibit differential vesicular ingestion rates for unmodified and non-enzymatically glycosylated rat albumin. While unmodified rat albumin is excluded from ingestion by endothelial micropinocytic vesicles, glycosylated albumin is avidly taken up by endocytosis. Interaction of albumin and glycosylated albumin with endothelium was studied with a double-label fluorescence assay of micropinocytosis. When glycosylated albumin was present at a concentration of 6% with respect to total albumin (the level found in "non diabetic" serum), only glycosylated albumin was ingested. At higher concentrations of glycosylated albumin (those found in diabetic serum), both albumin and glycosylated albumin are ingested. Glycosylation of endothelial membrane components results in stimulated ingestion of glycosylated albumin, persistent exclusion of unmodified albumin, and unaltered micropinocytic ingestion of native ferritin. These results indicate that nonenzymatic glycosylation of serum albumin may result in rapid vesicle-mediated extravasation of albumin. Chronic microvascular leakage of glycosylated albumin could contribute to the pathogenesis of diabetic microangiopathy.