A reliable method for preparing metaphase chromosomes from plant leaf tissues is described. The chromosomes are suitable for karyotype analysis and gene mapping by fluorescence in situ hybridisation (FISH). The method is based on enzymatic digestion of young leaf tissues (shoot-tips) after which the resulting protoplasts are treated hypotonically before being dropped onto microscopic slides. Compared to root-tip chromosomes, leaf chromosomes tend to be longer, or less condensed, and hence more karyotypically differentiated. Metaphase index in young leaf tissues is also very high. Metaphase spread consists of evenly and well-distributed chromosomes and this allows accurate counting. The plant used to demonstrate this method is birch (Betula L.), a group of tree species that has extremely small chromosomes. Root-tip chromosomes of these plants are difficult to obtain, as cutting does not produce roots readily. Seedling chromosomes do not represent the same genomic constitution as their mother trees due to introgressive hybridisation. Furthermore, sample collection in the field is convenient and actively growing leaf buds are available throughout the growing season. FISH experiments with these leaf chromosomes also give good results comparable to those obtained with root-tip chromosomes or even better as mapping on long or extended chromosomes has high resolution in general. Mapping of the 16S–28S ribosomal genes on birch leaf chromosomes has been shown to differentiate between birch species and therefore can accurately confirm their interspecific hybrids.
Altered intracellular Ca2+ dynamics are characteristically observed in cardiomyocytes from failing hearts. Studies of Ca2+ handling in myocytes predominantly use Fluo-3 AM, a visible light excitable Ca2+ chelating fluorescent dye in conjunction with rapid line-scanning confocal microscopy. However, Fluo-3 AM does not allow for traditional ratiometric determination of intracellular Ca2+ concentration and has required use of mathematic correction factors with values obtained from separate procedures to convert Fluo-3 AM fluorescence to appropriate CA2+ concentrations. This study describes methodology to directly measure intracellular Ca2+ levels using inactivated, Fluo-3 AM loaded cardiomyocytes equilibrated with Ca2+ concentration standards. Titration of Ca2+ concentration exhibits a linear relationship to increasing Fluo-3 AM fluorescence intensity. Images obtained from individual myocyte confocal scans were recorded, average pixel intensity values were calculated, and a plot is generated relating the average pixel intensity to known Ca2+ concentrations. These standard plots can be used to convert transient Ca2+ fluorescence obtained with experimental cells to Ca2+ concentrations by linear regression analysis. Standards are determined on the same microscope used for acquisition of unknown Ca2+ concentrations, simplifying data interpretaton and assuring accuracy of conversion values. This procedure eliminates additional equipment, ratiometric imaging, and mathematic correction factors and should be used to investigators requiring a straightforward method for measuring Ca2+ concentrations in live cells using Ca2+-chelating dyes exhibiting variable fluorescence intensity.
A new in vitro way of scoring the potential (proliferative- differentiative) of human haemopoietic stem cells (HHSC) is presented. We have applied it in the investigation of HHSC behaviour in normal bone marrow specimens under culture conditions. This system describes a modification of some existing culture assays for primitive HHSC function, and proliferation of the cobblestone area forming cell (CAFC) was determined by counting the cobblestone areas (CA) produced every week. The main steps of the assay are: (a) culture of MNC fraction on pre-established fibroblastic confluent layers from the M2. 10B4 mouse cell line; (b) weekly counting of CA over a period of 5 weeks; (c) weekly in situ observation of CA morphology; (d) enumeration of secondary progenitors per CA, in the 5th week. The CAM index, expressing the value of the CA kinetic line slope and the number of secondary progenitors per CA were evaluated as factors indicating HHSC proliferative and differentiative potential, respectively. This culture system has the potential to serve as an in vitro assay of human stem cell transplantation. It could be applied to evaluating the potential of HHSC contained in haemopoietic collections of diverse origin, only in combination with measurements of the starting number of CAFC.
Fluorescence image analysis provides quantitative data on fluorescence in situ hybridiza-tion signals (FISH), immunofluorescence labelings, Green Fluorescent Protein (GFP) expression and microarrays. It is a valuable tool for decision making in the fields of biology and medicine. The aim of this study was to evaluate the reproducibility of fluorescence intensity measurements and standardization when acquisitions are performed under various but well defined conditions. Fluorescent intensity of standard beads (Inspeck series, Molecular Probes) was repeatedly measured using an image analyzer and automated procedures. Images were acquired using several integration times and neutral filter sets. A standardization procedure was used for expressing the data in a same unit: data were multiplied by the light attenuation factor and were divided by the CCD integration times. Results show that 1) standardiza-tion is possible 2) accurate and reliable fluorescence measurements can be obtained and 3) specimens showing large differences in fluorescence intensity can be objectively compared. Moreover fluorescent test slides including fluorochrome solutions and altuglas slides were tested for shading correction and as overall test systems.
The technique of 2′,7′-dihydrodichlorofluorescin diacetate (H2DCF-DA)-derived fluorescence was applied to measurements of the oxidative burst reaction in plant cell suspension cultures in an automatic fluorometric multiwell microplate assay. The developed procedure was found to be versatile and effective for the determination of the oxidative burst reaction in plant cell cultures. Using this assay, cumulative production of reactive oxygen intermediates may be monitored and recorded non-destructively on a real-time scale for a large number of samples at frequent and continual time intervals for time course experiments. Through the use of various inhibitors and inducers or elicitors of the oxidative burst in combination with H2DCF-DA, this assay aids in the dissection of the signal transduction pathways and the determination of the origins of the oxidative burst in plant cells.
Although the manual counting chamber (hemacytometer) is the gold standard for counting cells, this method is subject to great variability due to the 'human factor'. The automated cell counter (Coulter Counter) can enumerate cells in less time and with greater accuracy than the hemacytometer by removing many of the steps in which errors are made. While the Coulter Counter (and others of its type) has been used for many years in the cell culture field, there have been few studies to validate its use with specific cell types. We conducted several experiments in which we assessed the accuracy of the Coulter Counter over counts made with a hemacytometer as well as validated its use for the counting of satellite cells and preadipocytes.
Acquisition of human corneal cells for culture is hindered not only by the scarcity of donor tissues but also by some of the standard enzymatic and mechanical isolation techniques. Good yields have been reported from full-thickness explant and sclero-limbal pieces. However, due to their greater proliferative capacity, fibroblasts will encroach and subsequently overwhelm epithelial cultures whichever technique is used. The novel approach presented here is to minimise this by removal of the whole stroma from the epithelial layers at the outset. This is achieved by selective sectioning with the Webb mini-microtome developed in the Norwich Eye Research Laboratory. The microtome can be sterilised by alcohol spraying or autoclaving and is small enough to use in the culture hood. A selective cut in the region of the Bowman’s membrane results in the isolation of the epithelium from the stroma and thus exposed, the basal epithelial layers are released from contact inhibition to allow growth. The stroma is further cut to produce multiple sections for the culture of fibroblasts. Both pure epithelial and stromal fibroblast cultures have been successfully generated in serum-enriched medium as well as defined serum-free media with growth supplements, from the corneo-scleral discs of donors of all ages.
Several reports indicate that the cytosol is acidified during apoptosis although the mechanism is not yet fully elucidated. The most acidic organelle found in the cell is the lysosome, raising the possibility that lysosomal proton release may contribute to the cytosolic acidification. We here describe methods for measurement of the cytosolic and lysosomal pH in U937 cells by a dual-emission ratiometric technique suitable for flow cytometry. Cytosolic pH was analysed in cells loaded with the fluorescent probe BCECF, while lysosomal pH was determined after endocytosis of FITC-dextran. Standard curves were obtained by incubating cells in buffers with different pH in the presence of the proton ionophore nigericin. Apoptosis was induced by exposure of cells to 10 ng/ml TNF-α for 4 h, and apoptotic cells were identified using a fluorescent marker for active caspases. By gating of control and apoptotic cells, the cytosolic and lysosomal pH were calculated in each population. The cytosolic pH was found to decrease from 7.2 ± 0.1 to 5.8 s± 0.1 and the lysosomal increased from 4.3 ± 0.4 to 5.2 ± 0.3. These methods will be useful in future attempts to evaluate the involvement of lysosomes in the acidification of the cytosol during apoptosis.
Chorionic villi are finger like projections, which surrounds the embryonic sac in early pregnancy and will later form the placenta. The outer layer of the chorionic villi consists of trophoblast cells. These cells are actively dividing and can be used for direct preparation or short-term culture for prenatal diagnosis of chromosomal abnormalities. We herein describe a 100% reproducible modified technique for one day direct culturing (direct prepara-tion) of trophoblast cells. Direct preparation of chorionic villi provides the physician with additional diagnostic information during prenatal diagnosis and genetic counseling. Direct preparation also eliminates the risk of maternal cell contamination. This method was 100% reproducible provided all the precautions mentioned herewith were taken into consideration and can be completed in 45 minutes upon arrival of the samples in the laboratories.
Studying the effects of microgravity on cell differentiation will enhance our understanding of fundamental biology and is indispensable for a sustained space program. Rauscher murine erythroleukemic cells were chosen as a model system to study erythroid cell differentiation aboard the International Space Station because these cells undergo differentiation in response to the natural inducer, erythropoietin, as well as various chemical inducers. We have now developed a method to quantify hemoglobin in Rauscher cells after weeks of fixation and storage required for such space biology experiments. By exploiting the pseudoperoxidase activity of hemoglobin and by using reagents that yield a soluble chromophore that freely passes out of fixed cells, we developed a highly specific and sensitive assay applicable to cells fixed as long as 4 months.
Two cell lines have been established from juvenile pilchards ( Sardinops sagax neopilchardus ) caught in waters off the Victorian coast of Australia. Following establishment of primary cultures derived from different pilchard tissues, using various cell culture media, a pilchard liver (PL) cell line and a pilchard heart (PH) cell line have been maintained in Eagle’s minimal essential medium supplemented with 10% foetal bovine serum for over four years. The cell lines have been cryopreserved in liquid nitrogen and can be recovered from storage with good cell viability. Stock cell cultures have been maintained at 20–22 °C on a continuous basis in normal atmosphere (100% air), with weekly subculture at a split ratio of 3:1. The origin of the cell cultures was confirmed by PCR analysis using primers designed to be specific for pilchard mitochondrial DNA. In addition, the liver cell line was cloned and both the parental cell line and clones thereof were shown to be susceptible to a broad range of marine and freshwater viral pathogens of fish.
Current methods to determine heat shock protein (Hsp) synthesis or accumulation in plant cells, such as Western blotting and biomet abolic labelling are either indirectly quantitative, labour-intensive or biohazardous. An optimal flow cytometric protocol was developed to measure the intracellular Hsp70/Hsc70 levels in tobacco protoplasts. After heat treatments, protoplasts were fixed in 2% paraformal dehyde-phosphate-buffered saline and dehydrated overnight in methyl cellusolve TM , followed by permeabilization with Triton X-100 (0. 1% in Protoplast Wash Fluid). Immunolabelling of Hsp70/Hsc70 was done for 1 hour with a mouse monoclonal antibody and detected by;R-Phycoerythrin-conjugated goat anti-mouse IgG using flow cytometry. Flow cytometry detected a significant 1. 2-fold increase in Hsp70/Hsc70 accumulation (P < 0. 001) in protoplasts, while Western blotting, quantified by image anal ysis, showed induction under similar conditions but at lower significance (P < 0. 05). The coefficients of variance for flow cytometry and Western blotting were 30. 7 and 49. 8 respectively. Optimum temperature of heat-induced Hsp70/Hsc70 accumulation in tobacco protoplasts occurred at 40 °C. Flow cytometry is proposed as a quantitative, more reproducible and rapid alternative to Western blotting for the detection of Hsp70 accumulation in plant cells.
Acid mine drainage (AMD) is a serious and persistent environmental pollution problem. At present, many studies have focused on the tailings pond's cover systems. This paper introduced the research results of using tin tailings from Laili mountain to make the covering layer of tailings pond. The first part included a detailed description of tailings characterization and acid production potential. On this basis, the hard layer (HL) was prepared and its feasibility as oxidation barrier was evaluated. It was found that when the proportion of tailings waste was 70%, the immobilization efficiency of heavy metals can reach more than 99.45%, and the pH of leaching solution was about 10.8. Moreover, the beneficial effect of solid waste addition on the HL was also verified. This suggests that HL as a post-mining restorative strategy has strong positive influence on pollution control.
This study focuses on recent improvement in epithelial monolayer cultures originating from whole extirpated Botryllus schlosseri (Urochordata) buds. Buds ( n = 2,000) were taken at different (‘A’ to ‘D’) blastogenic stages. We tested the suitability of 35 combinations of various substrates and media on attachment, cell spread, epithelial growth frequencies and on monolayer lifespans. Under favorable conditions, cultured buds at blastogenic stages ‘B’ to ‘D’ (but not stage ‘A’) started to attach to the substrates following a 3-day transient period that leads to formation of spheres and attached monolayers. Substrate type is important for the attachment and the development of monolayers. Under various culture conditions, some of stages ‘B’ and ‘C’ buds develop (3–20 days) one or more large (1 mm diameter) spheres. Stage ‘D’ buds develop monolayers (up to 20% of buds) without going through a sphere phase. Neither spheres nor attached monolayers of epithelium were observed in stage ‘A’ bud cultures. Spheres grew at a rate of 60 μm in diameter per day using specific medium types and did not attach unless the appropriate substrate was present. When attached, epithelial monolayers expanded at a rate of 200 μm in diameter per day, for 3–15 days, and subsequently detached and died. Sixteen types of media were tested. Medium and substrate combinations were found to determine epithelial lifespan. These results revealed significant improvements in the culture of epithelial monolayers from Botryllus palleal buds. However, an early senescence of the developed epithelial sheets (up to two weeks from onset of appearance) may indicate an internal ageing clock that should be taken into consideration in future approaches.
As the marine mussel Mytilus edulis is commonly used as a sentinel species, it would be useful to develop a primary culture of the target organs most often in contact with the marine environment. This study reports an improved method for dissociating the digestive gland and gills of M. edulis and considers the effect of mussel storage on cell viability and functionality before culture initiation. Viability and enzymatic activities such as those of esterase and peroxidase were monitored by flow cytometry, a sensitive, objective technique allowing large volumes of cells to be counted within a short time. A primary culture of digestive gland showed more than 75% viability after 72 h. Mussels were maintained in an aquarium containing clean, oxygenated seawater at 12 °C for two days before culture initiation, and dissociation was performed mechanically and chemically with Ca-Mg-free saline to obtain digestive gland cells. Application of nonspecific esterase activity, using fluorescein diacetate (FDA test) coupled with flow cytometry, characterised the functionality of digestive gland and gill cells in culture.
Three cell lines were established from muscle (SHMS), heart (SHHT) and swim bladder (SHSB) of snakehead ( Channa striatus ). The cells grew initially at 25 °C in L15 medium supplemented with 20% fetal bovine serum and have been subcultured 13–18 times since their initiation on June 25, 2002. Growth of the snakehead cells was serumdependent and plating efficiencies ranged from 22–29%. These snakehead cells grew well in RPMI 1640 and L-15 media, which are commonly used for cultivation of animal and mammalian cells and retained 95.9–96.6% cell viability following storage for 4 months in liquid nitrogen. Karyotyping indicated that these snakehead-derived cell lines remained diploid with a chromosome count of 44 at their early passage (passage 8–14). These cell lines were sensitive to CCV, VHSV, SVCV, IPN and SHRV; they were refractory to IHNV. These newly established cell lines are currently being used for the investigation of snakehead viral diseases in Hawaii and will be available for future isolation and study of snakehead viruses.
The present study describes a simple, rapid protocol for culture for limb tissue from individual 10.5-day post coitum mouse embryos that supports cartilage differentiation over a six-day period. This technique differs from other commonly used methods utilizing pooled limb tissue in that: 1) forelimbs from individual embryos were used as donor tissue; 2) limb tissue was dissociated by very gentle enzymatic digest (0.1% trypsin, 5 min); and, 3) cell suspensions were plated at a lower density (1 × 10 7 vs. 2 × 10 7 cells/ml) in a reduced volume of 3–5 μl. Under these modified conditions to increase limb cell yield from each embryo, histochemical and immunohistochemical analyses demonstrated reproducible for-mation of precartilage aggregates and subsequent overt chondrogenesis over a predictable time course. Using this culture protocol, analysis of limb mesenchyme from heterozygous hdf embryos, which bear an insertional mutation of the Cspg2 gene encoding the core protein of the chondroitin sulfate proteoglycan, versican, revealed an overall similar chondrogenic potential to that observed for wild-type littermates. This technique readily enables in vitro culture of limb bud mesenchyme from individual mouse embryos at this developmental stage and may be utilized by investigators to study the effects of the hdf and other transgenic mutations on mammalian limb development in vitro .
