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A comparison of immunomagnetic separation and culture, Reveal and VIP for the detection of E. coli O157 in enrichment cultures of naturally-contaminated raw beef, lamb and mixed meat products.

AIMS: The aims of this study were (i) to evaluate the specificity and sensitivity of three previously described PCR assays for the detection of E. coli O157 and, (ii) to compare PCR, culture, and two visual immunoassays (VIAs), BioSign and Path-Stik, for detecting E. coli O157 after enrichment culture and immunomagnetic separation (IMS) performed on various naturally contaminated raw beef, lamb and mixed meat products. METHODS AND RESULTS: Twelve sorbitol non fermenting (SNF) verocytotoxin-producing (VT+) E. coli O157, 6 SNF VT- E. coli O157, 4 sorbitol fermenting (SF) VT+ E. coli O157, 3 SF VT- E. coli O157, 23 E. coli belonging to 17 other serogroups and 12 organisms of other species were used to check the specificity of PCR reactions. Only one primer pair generated amplimers only with E. coli O157 and was used for all subsequent work. After enrichment culture and on inoculated minced beef samples, PCR was as sensitive as culture for detecting 9 of the 12 strains of E. coli O157, but up to 4 log10 more sensitive than culture for detecting three strains. Of the 120 samples of naturally contaminated meat products examined, 80 (67%) were positive by PCR, 70 (58%) were positive by BioSign, 69 (58%) were positive by culture and 67 (56%) were positive by Path-Stik. Eleven samples were positive by PCR and both VIAs, but negative by culture because culture plates were heavily overgrown with SF organisms making detection of any E. coli O157 present impossible. CONCLUSIONS: PCR and both VIAs compared well with culture of beads to CT-SMAC for detecting E. coli O157 after enrichment culture and IMS. PCR appeared to be the most sensitive method, but needed specialised equipment and was also the most expensive, laborious and technically demanding technique. Although lacking the sensitivity of PCR, the VIAs were of comparable sensitivity to culture and were extremely quick and easy to perform giving a result in less than 15 minutes. SIGNIFICANCE AND IMPACT OF THE STUDY: Culture techniques may fail to detect E. coli O157 retrieved by IMS due to overgrowth with other organisms.

Cell Culture Techniques↗

N-acetylcysteine partially reverses oxidative stress and apoptosis exacerbated by Mg-deficiency culturing conditions in primary cultures of rat and human hepatocytes.

OBJECTIVE: The effects of magnesium (Mg) deficiency on the rate of oxidative stress and apoptosis in primary cultures of human hepatocytes were compared to cultured rat hepatocytes. The possible reversion by N-acetylcysteine (NAC) in Mg-deficient culturing conditions was evaluated. METHODS: Incubations were conducted for up to 72 h in media containing a deficient (0-0.4 mM) or a physiological (0.8 mM) Mg concentration, and in the presence or absence of NAC after 24 h of culture in these Mg concentration conditions. RESULTS: We obtained similar profiles in terms of apoptosis and oxidative stress in primary cultures of human hepatocytes, as compared to rat hepatocytes, i.e. a Mg concentration-dependent effect on the caspase-3 activity and GSH levels after 72 h of culture, caspase-3 activity being highest and GSH levels being lowest in Mg-free cultures. The addition of NAC to culture media after the first 24 h of culture increased GSH concentrations. This was accompanied in Mg-deficient cultures by a decrease in both the caspase-3 activity and the lipid peroxidation. However, when culturing hepatocytes with physiological Mg concentrations, an increase in both caspase-3 activity and lipid peroxidation was observed. CONCLUSIONS: Our results indicate that Mg deficiency exacerbates the rate of apoptosis in cultured hepatocytes, associated with an increase in oxidative stress, the sensitivity of human hepatocytes being equivalent to that of rat hepatocytes. They also indicate a dual role of NAC and/or GSH, i.e. protective for hepatocytes placed in a Mg-deficient environment, while deleterious for hepatocytes placed in a Mg-physiological environment.

Acetylcysteine↗

Optimizing blood culture practices in pediatric immunocompromised patients: evaluation of media types and blood culture volume.

BACKGROUND: The optimal use of blood cultures to determine the etiology of febrile episodes in neutropenic children has not been well-defined. METHODS: Single volume blood cultures using the Pediatric ISOLATOR System (ISO), were compared with variable, weight-based culture volumes using the BACTEC 9240 Culture System (BAC). Additionally the value of routinely inoculating the BACTEC MYCO/F LYTIC culture vial (MFL) as well as the BACTEC AEROBIC/F culture vial (AF) was examined. RESULTS: A total of 2620 cultures had both ISO and BAC inoculated; 182 cultures were positive (7.0% of cultures); 97.8% of positive cultures were detected by the BAC (AF and/or MFL) vs.46.2% detected by the ISO. The advantage of the BAC over the ISO was statistically significant for overall recovery of isolates and bloodstream infections, including most individual organism categories. There were only two instances (one each of histoplasmosis and candidemia) in which a blood stream infection was detected by ISO only. All the isolates judged to be contaminants were recovered by BAC only. AF detected significantly more coagulase-negative Staphylococcus spp. than the MFL. Of the isolates 16%, representing 14% of the bloodstream infections (including Gram-negative infections), were detected by the MFL only. Infections were detected more quickly by BAC than by ISO (P < 0.0001). Among the BAC media types, AF was faster than MFL (P < 0.0001). CONCLUSIONS: Optimal yield of blood cultures in immunocompromised pediatric patients included the use of BAC with a weight-based, graduated volume of culture inoculation and routine use of both AF and MFL.

Bacteremia↗

Long-term culture of organotypic multicellular glioma spheroids: a good culture model for studying gliomas.

Gliomas, as well as other solid tumours, contain tumour stroma composed of connective tissue, macrophages, capillaries and other non-cellular constituents. Therefore, a homogeneous culture of tumour cells alone, as is often used as a culture model for gliomas, is not ideal to study all aspects of gliomas. In the present study we describe an alternative culture model, i.e. organotypic multicellular spheroids (OMS), that histologically closely resembles the tumour in vivo. Glioma explants, obtained at surgery from five patients, were cultured on agarose to form OMS, which were cultured for up to 16 weeks. At regular intervals, OMS were fixed and histological and immunocytochemical analyses were carried out. The histology as well as the immunocytochemical characteristics of the OMS proved to be almost unchanged after a culture period of 16 weeks. In contrast to monolayer cultures, glial fibrillary acidic protein (GFAP) expression in the OMS is preserved after 16 weeks of culture. However, in OMS from three out of five patients, small GFAP-negative cells appeared in the outer cell layers between 1 and 2 weeks of culture. Furthermore, after about 6 weeks of culture, the capillaries disappeared from the OMS. After prolonged culture, tumour cell heterogeneity, the cellular composition, and the histology of the OMS still closely resembled the tumour in vivo. It is suggested that OMS provide a good long-term culture model for the study of gliomas.

Adult↗

Somatomedin-C binding to cultured human fibroblasts is dependent on donor age and culture density.

Cultured fibroblasts have been used extensively to study age-related changes in the cellular response to serum stimulation. Since somatomedin-C (Sm-C) is an important growth factor in serum, we determined if there were age-related changes in Sm-C fibroblast receptor number or affinity and if culture density influenced these changes. Skin fibroblasts were obtained from six normal donors in three separate age groups and tested for their capacity to bind Sm-C. Sparse cultures (10-15K cells/well) derived from fetal donors had an affinity for Sm-C that was 4.7-fold greater than that of cultures derived from elderly (74-96 yr old) donors [9.4 +/- 0.2 (+/- SD) compared to 2.0 +/- 0.2 X 10(10) M-1]). When grown to high density (60-100K cells/well), the affinity of the fetal cultures was significantly reduced to 2.2 +/- 0.2 X 10(10) M-1 (P less than 0.001) and was not significantly different from the affinity of high density elderly donor cultures (2.3 +/- 0.4 X 10(10) M-1). Intermediate age donors (3-14 yr old) also had a significant reduction in receptor affinity with increasing density. Fetal donor cultures showed no density-dependent changes in receptor number. Fetal donor cells at low density had 5.2 +/- 1.0 X 10(4) receptors/cell compared to 5.9 +/- 0.6 X 10(4) receptors/cell in the high density cultures. In contrast, cells derived from donors aged 3-14 yr had 12.0 +/- 1.6 X 10(4) receptors/cell at 15K cells/well and 5.1 +/- 0.6 X 10(4) at 80K cells/well (P less than 0.05). Cultures from elderly donors had significantly greater mean receptor numbers per cell compared to fetal donor cells at four of five densities tested and had a significantly lower receptor number per cell with increasing culture density 25.2 +/- 1.2 X 10(4) (10-15K cells/well) compared to 5.2 +/- 0.2 X 10(4) (60-100K) cells/well. Thus, increasing donor age at low culture density was associated with an increase in receptor number per cell and a decrease in receptor affinity. At high culture densities, these differences were not detected. These changes in Sm-C receptor number and affinity at low density could lead to donor age-related changes in the cellular response to Sm-C.

Adolescent↗

Effect of serum-free co-culture and synchrony of recipients on development of cultured sheep embryos to fetuses.

The percentage of sheep embryos that continued to develop after collection and immediate transfer on d 2 after estrus was similar when phosphate-buffered saline with 10% fetal calf serum (PBSFCS, 45%), physiological saline (50%), or tissue culture medium 199 supplemented with 10% fetal calf serum (M199FCS, 47%) was used to flush embryos from oviducts. Co-culture of sheep embryos for 3 d with oviductal cells tended (P = .1) to reduce the percentage of embryos that developed to fetuses after transfer compared with those embryos transferred immediately. Tissue culture medium 199 supplemented with .3% BSA (M199BSA) was an adequate substitute for M199FCS for culture of sheep oviductal cells if tissue culture wells were pretreated with fibronectin. Estradiol in concentrations from 10 to 1,000 pg/ml and progesterone at concentrations of 1 or 10 ng/ml in M199BSA failed to stimulate embryo development during 3 d of co-culture beyond that seen in co-culture with M199FCS or M199BSA without added steroid. Transfer of sheep embyros co-cultured for 3 d in M199BSA or M199FCS to recipients synchronized with donors resulted in about 19% of the embryos developing to fetuses, whereas transfer to recipients that were in estrus 24 h after donors resulted in 33% of embryos developing to fetuses. The significant (P less than .05) improvement for delayed recipients may reflect the relatively lesser developmental rate of co-cultured embryos compared with that of embryos in vivo. Embryo development into fetuses was similar after co-culture in M199FCS or M199BSA co-cultures; therefore, serum is not required for the co-culture of sheep embryos.

Animals↗

Synovial fluid culture and blood culture in acute arthritis. A multi-case report of 90 patients.

The use of blood culture methods for culture of synovial fluid (SF) has been suggested to increase the yield of microbes from SF of patients with septic arthritis. We report on a study of 94 SF cultures of 90 adult patients with acute effusions of the knee joint. Three different culture methods were used: conventional agar plate culture, culture with lysis and centrifugation (Isolator) and broth enrichment (BACTEC 6A and 7A). Blood was cultured simultaneously from 76 patients. In the patients with clinical septic arthritis, the SF cultures were positive by all the methods in 8 patients and negative by all the methods in 19 patients. The contamination rate of the SF cultures was 3/215 in the patients without clinical septic arthritis. We conclude that reliable evidence of septic arthritis is emerged from a SF culture by a single method, and that the choice of culture method is less critical. In addition, we discuss the role of blood cultures in the diagnosis of acute arthritides.

Acute Disease↗

Globin synthesis in erythroid bursts that mature sequentially in culture. I. Studies in cultures of adult peripheral blood BFU-Es.

To study whether the culture time at which the burst populations mature influences the expression of fetal hemoglobin in bursts, we measured hemoglobin synthesis in cohorts of fully hemoglobinized erythroid bursts maturing sequentially in cultures of adult peripheral blood BFU-Es. In 13 of 15 experiments, a decline in gamma/gamma + beta ratio was noted as the culture time advanced. On the average, erythroid bursts that mature during the third culture week showed lower levels of fetal Hb synthesis compared to bursts that are already mature in the second culture week. The decline of gamma/gamma + beta ratio with culture time was also noted in erythroid bursts composed of immature erythroblasts. The enhanced HbF formation in peripheral blood BFU-E cultures is thus most pronounced among the bursts that become hemoglobinized early, and there is a tendency for normalization of HbF synthesis in bursts that mature in late culture days. These results can be interpreted by several alternatives, including the possibility that the expression of high HbF levels in the early days of adult BFU-E cultures is a reflection of premature commitment to terminal differentiation of progenitors that possess an active HbF program. The present data indicate that the variation of HbF synthesis with culture time should be taken into consideration when the influence of various culture conditions of HbF synthesis is studied in BFU-E cultures.

Adult↗

Secretion of amyloid precursor protein and laminin by cultured astrocytes is influenced by culture conditions.

Although normally quiescent, astrocytes in the adult brain respond to various types of brain injury by rapidly dividing, swelling, extending cellular processes, and expressing increased amounts of glial fibrillary acidic protein (GFAP). These phenomena are collectively referred to as "astrogliosis." Similarly, astroglia in primary culture stop dividing when they attain confluency, yet, as seen in situ, they retain their proliferative capacity for extended periods and resume rapid division when subcultured. To examine the impact of glial division on secretion of neurite-promoting factors, conditioned medium (CM) was removed from subconfluent, newly confluent, and long-term confluent ("aged") neonatal rat astrocyte cultures, and from aged confluent cultures that had been repassaged, "lesioned" (scraping with a rubber policeman), or triturated 3 days before harvest. Secretion of neurite-promoting factor(s) by glial cells into these CM was then assayed by treating neuroblastoma cultures with these various CM and quantitating neurite elaboration. Extensive neurite sprouting was elicited by CM from cultures just reaching confluency and from repassaged, lesioned, or triturated cultures. CM from aged confluent cultures did not induce sprouting. These results indicate that secretion of neurite-promoting factor(s) is regulated by glial division, and suggest that gliosis in situ may contribute to neurite sprouting by similar mechanisms. Immunoblot analysis demonstrated the presence in CM of varying amounts of laminin and amyloid precursor protein (APP), including isoforms containing the Kunitz-type protease inhibitor domain. CM from subconfluent cultures contained trace amounts of these proteins, but CM from cultures just reaching confluency contained significant amounts. Although CM from aged cultures contained barely detectable levels of either protein, trituration or repassage of aged cultures dramatically increased secretion of these proteins. APP- and laminin-enriched CM fractions promoted neuritogenesis to a similar level as respective unfractionated CM; anti-APP and anti-laminin antisera blocked this effect. Purified human brain APP promoted neuritogenesis when added to non-conditioned medium and aged CM. Increased secretion of APP and laminin therefore mediates at least a portion of CM-induced neuronal sprouting; these proteins may perform analogous functions during astrogliosis in situ.

Amyloid beta-Protein Precursor↗

Comparative functional study of clonal insulin-secreting cells cultured in five commercially available tissue culture media.

The electrofusion-derived rat insulin-secreting cell line BRIN-BD11 was cultured in five different commercially available media to determine the optimum medium for the in vitro maintenance of such clonal cell lines. Cells were cultured in RPMI-1640, DMEM, McCOY'S, F-12K, or MEM culture medium supplemented with 10% (v/v) fetal bovine serum and antibiotics (100 U/ml penicillin and 0.1 g/L streptomycin). Insulin secretion studies performed after 10 days revealed RPMI-1640 to be the best performing medium in terms of insulin secretory responsiveness to a range of stimuli including glucose, L-alanine, L-arginine, carbachol, and glibenclamide. Insulin release was significantly decreased (p < 0.01 to p < 0.05) in all other media compared to RPMI-1640. Only the cells cultured in RPMI-1640 and DMEM showed a significant glucose-induced insulin secretory response (p < 0.01 and p < 0.05). McCOY'S gave the next best result followed by F-12K and MEM. After the 10-day culture period, the highest insulin content was found in cells cultured in RPMI-1640 and DMEM with significantly lower levels of insulin in cells cultured in McCOY'S, F-12K, and MEM (p < 0.01 to p < 0.001). RPMI-1640 was used for further studies to investigate the effects of 5.6-16.7 mmol/L glucose in culture on the secretory responsiveness of BRIN-BD11 cells. Significant responses to a number of nonglucidic secretagogues were seen following culture at 5.6 and 16.7 mmol/L glucose, although responsiveness was less than after culture with 11.1 mmol/L glucose. At 16.7 mmol/L glucose culture, glucose-stimulated insulin release was abolished.

Alanine↗

Co-culture with the striatum attenuates N-methyl-D-aspartate cytotoxicity in dopaminergic neurons of rat mesencephalic slice cultures.

We examined the role of striatal cells in cytotoxicity induced by N-methyl-D-aspartate (NMDA) in dopamine (DA) neurons in rat mesencephalic slice culture. Coronal sections were prepared from 2- and 3-day-old rat brains and cultured using the interface culture method for 2-3 weeks before the NMDA cytotoxicity experiment. The exposure of mesencephalic cultures without striatum (single culture) to NMDA (10-300 microM) for 24 hr reduced the number of DA neurons in a concentration-dependent manner. The co-administration of the non-competitive NMDA-receptor antagonist significantly inhibited the neurotoxic effect of NMDA. When mesencephalon and striatum were kept in contact and co-cultured (contacting co-cultures), the growth of DA fibers into the striatal part was observed. In the contacting co-cultures with striatum, the minimal effective concentration for NMDA cytotoxicity was higher than that in single cultures. The contacting co-cultures with cerebellum did not alter the NMDA cytotoxicity. When the mesencephalon and striatum slices were kept apart and co-cultured, the co-cultures showed neither an outgrowth of DA fibers to the striatum nor any effect on the NMDA cytotoxicity. These results suggest that the projection of rat mesencephalic DA neurons to the striatum attenuates the NMDA cytotoxicity in DA neurons themselves.

Animals↗

Growth of human normal erythroid progenitors in liquid culture: a comparison with colony growth in semisolid culture.

Most studies of erythropoiesis in vitro have employed cloning methods in semisolid medium. We have recently described a two-step liquid culture procedure that supports the proliferation and differentiation of human erythroid progenitors. In the present study, we have modified the procedure to allow large-scale cultures of erythroid cells derived from normal donors. The culture is divided into two phases. In the first phase, which is erythropoietin (Epo) independent, the early erythroid progenitors multiply and differentiate. In the second, Epo-dependent phase, they mature into orthochromatic normoblasts and enucleated erythrocytes. Using this procedure, erythroid cell yield reached 7.5 x 10(6)/ml and a total of 7 x 10(8) cells could be harvested per blood unit. A comparison of the growth of erythroid cells in liquid culture to their colony growth in semisolid culture indicated that cell growth was superior: 1) in liquid culture in terms of cell yield per originally cultured mononuclear cell, 2) per ml culture and per culture surface area and in the purity of the resultant erythroid cell population. In addition, it permits easier manipulation of the culture condition and components and sampling of greater than 1 x 10(7) cells at each maturation stage subsequent to the proerythroblast stage. This liquid culture procedure might provide an important experimental tool for studying erythroid cell development.

Cell Division↗

Low-density cultures of bovine chondrocytes: effects of scaffold material and culture system.

Chondrocytes were seeded on either agarose or polyglycolic acid (PGA) unwoven meshes at 10 million cells/ml of scaffold volume to evaluate the effect that these two biomaterials have on the low-density culture of chondrocytes in a rotating-wall bioreactor. For both static and bioreactor culture, agarose constructs contained more glycosaminoglycan than their PGA counterparts. However, the PGA constructs contained more collagen for both culture conditions when compared to agarose. For the low seeding density of this study, PGA constructs cultured in the bioreactor did not outperform static cultures when comparing collagen content after 8 weeks. The mechanical properties of the PGA constructs also did not improve with culture time. Similar results were observed with the agarose culture, though both static- and bioreactor-culture agarose constructs exhibited increases in aggregate modulus at the end of the culture period. As in PGA culture, chondrocytes cultured in agarose may require a higher density to reap the benefits of the bioreactor environment.

Animals↗

Maintenance of granulopoiesis in long-term bone marrow cultures from W/Wv mice and effects of lipopolysaccharide on granulopoiesis in culture.

An attempt was made to establish long-term cultures of marrow cells from genetically anaemic W/Wv mice. Two batches of horse sera were used. One batch of horse serum (HS-lot A) supported long-term maintenance (up to 20 weeks) of granulopoiesis in vitro. The number of suspension cells in W/Wv marrow culture was maintained at the same level as that in the control +/+ culture, but the number of granulocyte-macrophage progenitor cells (GM-CFC) and the ratio of immature to mature granulocytes were at a lower level than those in +/+ culture. These data suggest that haemopoietic progenitors in W/Wv cultures maintain a higher level of differentiation, and hence an increased self-renewal than those in +/+ cultures. Another batch of horse serum (HS-lot B) was less effective in the maintenance of the cultures, and the cultures deteriorated within 10 weeks. Addition of bacterial lipopolysaccharide (LPS) induced increased granulopoiesis in +/+ cultures, whereas such treatment resulted in the depletion of suspension cells in W/Wv cultures. The results suggest that haemopoietic cells of W/Wv mouse cannot cope with the strong stimulus for differentiation that occurs after the administration of LPS, although the cells can continue a moderately increased self-renewal and differentiation, as indicated by the results in the culture with HS-lot A.

Anemia, Macrocytic↗

Inhibitory effect of Sertoli cell-cultured media on LH binding to mouse Leydig cells in culture.

The aim of this study is to examine the influence of Sertoli cells on LH binding to Leydig cells in culture in immature mice. Leydig cells and Sertoli cells were obtained from the testes of immature C57BL/6Ncrj mice and were cultured in serum-free medium for 7 days. The LH binding to Leydig cells and the FSH binding to Sertoli cells were dependent on incubation time, the number of cells, and the amount of labelled hormone added. The dissociation constant for LH binding to Leydig cells was 7.3 x 10(-10) M. Co-culture of Leydig cells with Sertoli cells for 7 days decreased LH binding to Leydig cells. The binding was 34.9% of that to Leydig cells cultured alone. After cultivation of Leydig cells with spent Sertoli cell-cultured medium (SM) for the last 4 days of the 7-day culture period, LH binding to Leydig cells decreased to as low as 17.4% of that of the controls. For the controls, LH binding was measured in Leydig cells cultured in spent Leydig cell-cultured medium (LM). There was no difference between SM- and LM-cultures in the final survival rate or the percentage of cells showing histochemically demonstrated 3 beta-hydroxysteroid dehydrogenase activity. These data suggest that some factor or factors are secreted from the cultured Sertoli cells and inhibit the binding of LH to Leydig cells in culture.

Animals↗

Optimization of culture conditions for the preservation of monkey pancreatic islets in culture.

Culturing of islets is essential for various purposes before transplantation. It is necessary to establish optimal culture conditions for each animal species for their preservation in culture. In this study, attempts were made to preserve the Indian bonnet monkey islets in culture. The islets were isolated from monkey pancreas by the collagenase digestion method. They were separated from acinar cells by dextran density-gradient centrifugation. They were preserved in a humidified atmosphere of 5% carbon dioxide and 95% air for 7 days. The culture medium used was RPMI-1640. Various optimal conditions such as volume of the culture medium used, number of islets in one culture dish, concentration of glucose in culture medium, and fetal calf serum percentage were tested for their better preservation in culture. After the culture period, they were tested for their insulin secretory capacity by exposing them to various secretagogues. Histologic appearance of the cultured islets also was examined. Both insulin secretory characteristics and histologic structure were found to be normal.

Animals↗