A direct comparison of procedures for the detection of mycoplasma in tissue culture

Application of Novel Gill Cell Line from Lates calcarifer for Recognizing Metals Using Probes

Lates calcarifer (Bloch) is a potential candidate fish species for culture in marine and brackishwater. A continuous gill cell line was derived from L. calcarifer by the explant culture method and has been passaged for 132 times, in Leibovitz's L-15 medium containing 10% fetal bovine serum (FBS) at 28 °C. The cells showed a rate of recovery between 90 and 95% after being successfully cryopreserved at various passage levels and formed monolayer in 2-3 days without any morphological changes. Immunophenotypic analysis of the SBG cell line revealed that they are of epithelial origin. Polymerase chain reaction assay using mitochondrial 12S rRNA primer specific to L. calcarifer was used to confirm the authenticity of the established gill cell line origin from seabass. The transfection efficiency was evaluated in Seabass Gill (SBG) cell line using pEGFP-N1 and Lipofectamine™ 3000. Transfection efficiency was found to be between 13 and 16%. The cytotoxicity of three different metal detecting probes was evaluated by MTT and Alamar blue assays to determine safe concentration. The result revealed that SBG cell line can be applied for recognition of metals using probes. The current study established, for the first time, a gill-derived cell line (SBG) from Lates calcarifer and its application for the detection of intracellular indium, mercury, and lutetium ions by specific fluorescent probes.

Bacterial Amyloid and DNA are Important Constituents of Senile Plaques: Further Evidence of the Spirochetal and Biofilm Nature of Senile Plaques

It has long been known that spirochetes form clumps or micro colonies in vitro and in vivo. Cortical spirochetal colonies in syphilitic dementia were considered as reproductive centers for spirochetes. Historic and recent data demonstrate that senile plaques in Alzheimer’s disease (AD) are made up by spirochetes. Spirochetes, are able to form biofilm in vitro. Senile plaques are also reported to contain elements of biofilm constituents. We expected that AβPP and Aβ (the main components of senile plaques) also occur in pure spirochetal biofilms, and bacterial DNA (an important component of biofilm) is also present in senile plaques. Histochemical, immunohistochemical, and in situ hybridization techniques and the TUNEL assay were used to answer these questions. The results obtained demonstrate that Aβ and DNA, including spirochete-specific DNA, are key components of both pure spirochetal biofilms and senile plaques in AD and confirm the biofilm nature of senile plaques. These results validate validate previous observations that AβPP and/or an AβPP-like amyloidogenic protein are an integral part of spirochetes, and indicate that bacterial and host derived Aβ are both constituents of senile plaques. DNA fragmentation in senile plaques further confirms their bacterial nature and provides biochemical evidence for spirochetal cell death. Spirochetes evade host defenses, locate intracellularly, form more resistant atypical forms and notably biofilms, which contribute to sustain chronic infection and inflammation and explain the slowly progressive course of dementia in AD. To consider co-infecting microorganisms is equally important, as multi-species biofilms result in a higher resistance to treatments and a more severe dementia.

Development and characterization of a new gill cell line from air breathing fish Channa striatus (Bloch 1793) and its application in toxicology: direct comparison to the acute fish toxicity

A new cell line, Channa striatus gill (CSG), derived from the gill tissue of murrel, was established and characterized. The CSG cell line was maintained in Leibovitz's L-15 supplemented with 10% fetal bovine serum and has been subcultured more than 92 times. This cell line was able to grow in a range of temperatures from 22 to 32°C with optimal growth at 28°C. The plating efficiency was very high (52.21%) and doubling time was approximately 37h. The gill cell line was cryopreserved at different passage levels and revived successfully with 85% survival. Polymerase chain reaction amplification of mitochondrial 16S rRNA using primer specific to C. striatus confirmed the origin of this cell line from murrel. The cell line was further characterized by immunocytochemical analysis, chromosome number, transfection and mycoplasma detection. The cytotoxicity of endosulfan was assessed in CSG cell line using apoptosis assay, comet assay, mitochondrial alteration and five other endpoints such as Rhodamine 123 uptake, 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, neutral red assay, Alamar Blue assay and Methylene Blue protein assay. Acute toxicity study on fish was conducted by exposing murrel for 96h to endosulfan under static conditions. Statistical analysis revealed good correlation with r(2)=0.972-0.997 among the five endpoints. Linear correlations between the in vivo lethal concentration 50 (LC50) and each in vitro effective concentration 50 (EC50) were highly significant. The present study highlights the development of a new gill cell line from an air breathing fish that could be used as an alternative in vitro tools for studying pesticide toxicity in fish.

Development, characterization and application of a new fibroblastic-like cell line from kidney of a freshwater air breathing fish Channa striatus (Bloch, 1793)

A new cell line, Channa striatus kidney (CSK), derived from the kidney tissue of murrel, was established and characterized. The CSK cell line was maintained in Leibovitz's L-15 supplemented with 10% fetal bovine serum and has been subcultured more than 140 times. This cell line was able to grow in a range of temperatures from 22 to 32°C with optimal growth at 28°C. The plating efficiency was very high (67.54%) and doubling time was approximately 29h. The kidney cell line was cryopreserved at different passage levels and revived successfully with 90-92% survival. Polymerase chain reaction amplification of mitochondrial 16S rRNA using primer specific to C. striatus confirmed the origin of this cell line from murrel. The cell line was further characterized by chromosome number, transfection and mycoplasma detection. A marine fish nodavirus was tested to determine the susceptibility of this new cell line. The CSK cell line was found to be susceptible to nodavirus and the infection was confirmed by cytopathic effect (CPE), reverse transcriptase-polymerase chain reaction (RT-PCR), immunodot blot, enzyme linked immunosorbent assay (ELISA), virus replication efficiency and real time RT-PCR. The present study highlights the development and characterization of a new kidney cell line from an air breathing fish that could be used as an in vitro tools for propagation of fish viruses and gene expression studies.

Modern uses of electron microscopy for detection of viruses

Electron microscopy, considered by some to be an old technique, is still on the forefront of both clinical viral diagnoses and viral ultrastructure and pathogenesis studies. In the diagnostic setting, it is particularly valuable in the surveillance of emerging diseases and potential bioterrorism viruses. In the research arena, modalities such as immunoelectron microscopy, cryo-electron microscopy, and electron tomography have demonstrated how viral structural components fit together, attach to cells, assimilate during replication, and associate with the cellular machinery during replication and egression. These studies provide information for treatment and vaccine strategies.

Isolation of immunoresistant human glioma cell clones after selection with alloreactive cytotoxic T lymphocytes: cytogenetic and molecular cytogenetic characterization

Intratumoral heterogeneity and genetic instability within gliomas may allow intrinsically immunoresistant (IR) cells to escape alloreactive cytotoxic T lymphocyte (aCTL) cellular immunotherapy. The potential existence of aCTL-resistant variants prompted us to investigate whether cellular immunotherapy resistant glioma models could be isolated. To generate the models, repeated intermittent or continuous selective pressure (ISP or CSP) with multiple aCTL populations was applied to a low-passage glioblastoma cell explant, 13-06-MG, obtained from a patient at initial diagnosis. IL-6 and IL-8 secretion was greater in coincubates of aCTL cells with 13-06-ISP and 13-06-CSP immunoselected cells than those with 13-06-MG parental cells. Initially, the immunoselected cells were less sensitive to aCTL lysis; however, the reduced aCTL-sensitivity was not maintained upon further selection. We therefore isolated IR clones from continuously immunoselected cells (13-06-CSP). The frequency of IR clones was 1-6 cells per 10,000 immunoselected cells. Two clones selected for further study, 13-06-IR29 and 13-06-IR30, resisted aCTL lysis in the absence of immunoselective pressure. Cytogenetic analyses revealed structural anomalies and genomic imbalances unique to the IR clones. Based on these findings, a hypothetical model is proposed that traces the origin of the IR clones to a clonal variant within the 13-06-CSP and 13-06-MG populations.

In situ staining with DNA-binding fluorescent dye, Hoechst 33258, to detect microorganisms in the epithelial cells of oral leukoplakia

This study was performed to investigate the presence of microorganisms in the epithelial cells of leukoplakia. Frozen sections of 20 specimens of leukoplakia were stained with DNA-binding bisbenzimide Hoechst 33258. As a control, 20 specimens of normal oral mucosa and five specimens of normal skin were used. In all preparations of leukoplakia, small granular fluorescing structures were observed within the cytoplasm of the epithelial cells, predominantly within the cytoplasm of prickle cells, although the amount of the granular structures varied between specimens, layers of the epithelium and even areas of the epithelium within a single section. Less granular structures were observed, or none at all, in the cytoplasm of the epithelial cells of normal mucosa. No structures were observed in the cytoplasm of the epithelium of skin. The results in this study strongly suggest that microorganisms are present in the epithelial cells of oral mucosa, and that they are closely associated with the development of oral leukoplakia. It is postulated that the microorganisms in the epithelial cells could be bacteria, particularly mycoplasmas.

Tumor-specific proteolytic processing of cyclin E generates hyperactive lower-molecular-weight forms

Cyclin E is a G(1) cyclin essential for S-phase entry and has a profound role in oncogenesis. Previously this laboratory found that cyclin E is overexpressed and present in lower-molecular-weight (LMW) isoforms in breast cancer cells and tumor tissues compared to normal cells and tissues. Such alteration of cyclin E is linked to poor patient outcome. Here we report that the LMW forms of cyclin E are hyperactive biochemically and they can more readily induce G(1)-to-S progression in transfected normal cells than the full-length form of the protein can. Through biochemical and mutational analyses we have identified two proteolytically sensitive sites in the amino terminus of human cyclin E that are cleaved to generate the LMW isoforms found in tumor cells. Not only are the LMW forms of cyclin E functional, as they phosphorylate substrates such as histone H1 and GST-Rb, but also their activities are higher than the full-length cyclin E. These nuclear localized LMW forms of cyclin E are also biologically functional, as their overexpression in normal cells increases the ability of these cells to enter S and G(2)/M. Lastly, we show that cyclin E is selectively cleaved in vitro by the elastase class of serine proteases to generate LMW forms similar to those observed in tumor cells. These studies suggest that the defective entry into and exit from S phase by tumor cells is in part due to the proteolytic processing of cyclin E, which generates hyperactive LMW isoforms whose activities have been modified from that of the full-length protein.

Novel splice variants of cyclin E with altered substrate specificity

Cyclin E, a G(1) cyclin, is overexpressed and present in low molecular weight (LMW) isoforms in breast cancer cells and tumor tissues. In this study we have examined the possibility that the shortened mRNA splice variants could give rise to tumor-specific cyclin E LMW proteins. We used the Splice Capture method to identify, enumerate and isolate known spliced mRNAs and to look for previously undetected mRNA forms of cyclin E that might be translated into the LMW proteins. We show that a new splice variant of cyclin E found in tumor cells isolated by the Splice Capture strategy, named Delta48, activates CDK2 more robustly than full-length cyclin E when assayed from transiently transfected cells with the natural substrate GST-Rb. We also found the Splice Capture method to be superior to the conventional RNase protection assay in analyzing the cyclin E mRNA present in normal and tumor cells. Splice Capture enumerated the relative abundance of known forms of cyclin E mRNA and easily discovered new splice variants in both normal and tumor cells. We conclude that the abundance of cyclin E splice variants in cells may represent a novel form of regulation of cyclin E, and if translated they show altered substrate specificity compared to the full length form of cyclin E.

UCN-01-mediated G1 arrest in normal but not tumor breast cells is pRb-dependent and p53-independent

In this study we investigated the growth inhibitory effects of UCN-01 in several normal and tumor-derived human breast epithelial cells. We found that while normal mammary epithelial cells w were very sensitive to UCN-01 with an IC(50) of 10nM tumor cells displayed little to no inhibition of growth with any measurable IC(50) at low UCN-01 concentrations (i.e. 0-80 nM). The UCN-01 treated normal cells arrested in G1 phase and displayed decreased expression of most key cell cycle regulators examined, resulting in inhibition of CDK2 activity due to increased binding of p27 to CDK2. Tumor cells on the other hand displayed no change in any cell cycle distribution or expression of cell cycle regulators. Examination of E6- and E7-derived strains of normal cells revealed that pRb and not p53 function is essential for UCN-01-mediated G1 arrest. Lastly, treatment of normal and tumor cells with high doses of UCN-01 (i.e. 300 nM) revealed a necessary role for a functional G1 checkpoint in mediating growth arrest. Normal cells, which have a functional G1 checkpoint, always arrest in G1 even at very high concentrations of UCN-01. Tumor cells on the other hand have a defective G1 checkpoint and only arrest in S phase with high concentrations of UCN-01. The effect of UCN-01 on the cell cycle is thus quite different from staurosporine, a structural analogue of UCN-01, which arrests normal cells in both G1 and G2, while tumor cells arrest only in the G2 phase of the cell cycle. Our results show the different sensitivity to UCN-01 of normal compared to tumor cells is dependent on a functional pRb and a regulated G1 checkpoint.

The transport of acidic amino acids and their analogues across monolayers of human intestinal absorptive (Caco-2) cells in vitro

The X-AG system, a sodium-dependent, acidic amino-acid transport system has been implicated in the transport of L-aspartate and L-glutamate across monolayers of human Caco-2 cells, an in vitro model of intestinal absorption. This system, which shares many properties with the L-glutamate carrier present in the human jejunum, is highly saturable (> 95% at 50 microM), vectorial (apical-to-basolateral >> basolateral-to-apical) and sodium-, pH- and temperature-dependent. L-Aspartate was also transported against a 10-fold reverse concentration gradient. These data are consistent with a major (saturable) carrier-mediated pathway superimposed onto a minor non-saturable (diffusional) pathway. The carrier has an absolute sodium-dependence and the Michaelis constants for the sodium-dependent transport component (Km) for L-aspartate and L-glutamate were 56 +/- 3 microM and 65 +/- 6 microM, respectively. Cross-inhibition studies showed that strong interaction with the carrier was limited to close analogues of the natural substrates. Potent inhibitors included L-aspartate, D-aspartate (Ki, 70 microM), L-glutamate (Ki 180 microM) and threo-beta-hydroxy-DL-aspartate (Ki, 55 microM), while partial inhibitors included alpha-methyl-DL-aspartate, D-glutamate, L-asparagine, L-proline and L-alanine. Replacement of the side-chain -COO- group (aspartate) with -SO-3 (L-cysteate, Ki, 65 microM) or -(H)P(O)O- (DL-3-(hydroxyphosphoryl)alanine, Ki, 60 microM) maintained strong interaction with the carrier while -As(O)(OH)O- (DL-3-arsonoalanine, Ki, 1100 microM) and -P(O)(OH)O- (DL-3-phosphonoalanine, Ki, 3270 microM) were much more weakly bound, with the larger, but probably less ionised, arsono analogue being more tightly bound than the phosphono compound. The corresponding analogues of glutamate (homologous extension of the methylene chain) showed negligible interaction. We conclude that Caco-2 monolayers are a relevant experimental model for the study of the transport of acidic amino acids and their analogues in man.

Fatty acid uptake and metabolism in CaCo-2 cells: eicosapentaenoic acid (20:5(n-3)) and oleic acid (18:1(n-9)) presented in association with micelles or albumin

In vivo, long-chain fatty acids are incorporated into bile salt micelles, which solubilize the hydrophobic fatty acids before they are transported across the unstirred water layer to the intestinal brush border membrane. In the present study we have used CaCo-2 cells, cultured on filter membranes as a model of human enterocytes, and compared presentation of fatty acids bound to albumin with a micellar form. Absorption of eicosapentaenoic acid and oleic acid from micellar solutions was 4-times faster than from fatty acid-albumin complexes after 5 h incubation, and resulted in a corresponding increase in triacylglycerol synthesis and secretion. Mass determination of newly synthesized, cell-associated triacylglycerol after 5 h incubation, indicated a 5-fold increase in cells exposed to a micellar solution versus albumin-complexed fatty acids. A 2-fold larger fraction of the absorbed fatty acids was incorporated into triacylglycerol than into phospholipids when the fatty acids were presented as micelles. Analysis by resistive pulse technique showed that secreted lipoproteins of density less than 1.006 g/ml were in the same size-range as chylomicrons derived from human plasma. In spite of an increased amount of secreted triacylglycerol from cells supplemented with micellar fatty acids, there was no increase in the mean size of these particles. Synthesis and secretion of triacylglycerol in cells exposed to eicosapentaenoic acid and oleic acid were similar regardless of whether the fatty acids were presented to the cells associated with albumin or micelles, although the total amount of triacylglycerol synthesized and secreted was highest with micelles. When incubating CaCo-2 monolayers with eicosapentaenoic acid or oleic acid bound to albumin, a similar amount of radioactivity was released as CO2 and acid soluble products into the medium with less than 3% of the lipids being oxidized after 5 h of incubation. The oxidation rate of fatty acids in cells incubated with micelles was increased 40 to 100%. In conclusion, micellar fatty acids are absorbed, metabolized and influence secretion of lipoprotein particles to a higher extent than albumin-bound fatty acids in CaCo-2 cells, and there is no major difference between eicosapentaenoic acid and oleic acid.

Post-transcriptional regulation of interferon-alpha 4 subtype production by lymphoblastoid cells

The constitutive production of interferon-alpha (IFN-alpha) subtypes by the lymphoblastoid cell lines, Namalwa, Daudi and Raji, was investigated using sensitive and semi-quantitative flow cytometric techniques. Further, we sought to determine whether the previously described failure of these cell lines to produce IFN-alpha-4 was a result of the deletion of the IFN A4 gene. Cytoplasmic production of IFN-alpha-2 and IFN-alpha-4 was assessed using IFN-alpha subtype-specific antipeptide antibodies and FITC-labelled secondary antibodies in indirect immunofluorescence-flow cytometry studies. The constitutive production of IFN-alpha-2 was detected in all three cell lines. Significant increases in fluorescence representing increased production of IFN-alpha-2 and possibly other IFN-alpha subtypes were detected after induction by Sendai virus. Approximately 100 per cent of cells in the Namalwa, Daudi and Raji cell populations contained IFN-alpha-2 before and after induction. However, no cells from the same cell populations contained the IFN-alpha-4 subtype. Analysis of genomic DNA isolated from the lymphoblastoid cells using the Polymerase Chain Reaction (PCR) and oligonucleotide primers specific for IFN A2 or IFN A4 confirmed the presence of the genes encoding both IFN-alpha subtypes. Furthermore, using reverse transcriptase-PCR amplification, mRNAs for both IFN-alpha-2 and IFN-alpha-4 were detected. Therefore, in contrast to some leukaemias and derived cell lines where IFN A genes have been deleted, these cell lines of B cell lineage exhibit selective expression of IFN A genes, as a result of altered transcriptional/translational control of IFN-alpha expression.

Different interactions of interferon-alpha subtypes at the surface of epithelial and lymphoid cells

The interaction of different interferon (IFN)-alpha subtypes with different cell types was investigated using a unique monoclonal antibody (MAb), I-4-A. This MAb reacts in immunoassays equally with IFN-alpha 2b and IFN-alpha 4a, but does not inhibit the binding of IFN to cell receptors. 125I-labeled I-4-A reacted with IFN-alpha 4a and IFN-alpha 2b bound to receptors on Daudi cells. However, in a "double assay" developed using Daudi cells to measure antiviral and antiproliferative activity, I-4-A neutralized both activities of IFN-alpha 4a, but neither of IFN-alpha 2b. Similarly, in studies on the activation of natural killer (NK) cells, I-4-A neutralized the effect of IFN-alpha 4a but not that of IFN-alpha 2b. In contrast, when cell lines other than lymphoid were studied, e.g., HEp 2 and WISH cells, I-4-A neutralized the antiviral activity of both IFN-alpha subtypes. The neutralization of one IFN-alpha subtype but not another on lymphoid cells suggests a difference either in the receptor-bound form of the subtypes, or in subsequent interactions prerequisite for activation of these cells. Furthermore, the neutralization of a particular IFN subtype, alpha 2b, on epithelial-derived but not lymphoid cells suggests differences in the IFN-receptor complex or the mechanisms of cell activation between these cell types. An implication from these studies is that some IFN-alpha subtypes can exert different functions on lymphoid and epithelial cells.

Proline uptake by monolayers of human intestinal absorptive (Caco-2) cells in vitro

Monolayers of the Caco-2 human intestinal cell line exhibit active and passive uptake systems for the imino acid L-proline. The active transport component is saturable and it is responsible for about two thirds of the observed flux over the nanomolar concentration range, at 37 degrees C and pH 7.4. In contrast to L-phenylalanine, specific L-proline uptake has a high degree of sodium dependency and the efficiency of the carrier system is significantly reduced when protein synthesis (cycloheximide), Na+/K(+)-ATPase (ouabain) or cellular metabolism (sodium azide) are inhibited. The expression of the L-proline carrier by Caco-2 cells was under some degree of nutritional control. Glucose deficiency, over the time scale of the experiment, had no effect. The temperature-dependence of the specific uptake process followed the Arrhenius model with an apparent activation energy of 93.5 kJ nmol-1. This pathway also displayed Michaelis-Menten concentration-dependence with a Ksdm of 5.28 mM and a maximal transport flux (Jsdmax) of 835 pmol min-1 (10(6) cells)-1. Although the passive component was unchanged, the pH of the donor phase exerted a profound effect on the active carrier component. Within the physiological pH range a local maximum efficiency was found at pH 7.4 but dramatic increases were noted as pH 5.0 was approached. In competition studies, with 100-fold excess of a second amino acid, strong inhibition of uptake was found with alpha-aminoisobutyric acid, L-alanine and L-serine whereas moderate inhibition was observed with glycine, D-proline and gamma-aminoisobutyric acid. Aromatic and branched amino acids showed weak (L-valine) or no interaction (L-phenylalanine, L-leucine) with the carrier system. These data indicate that the carrier system for the uptake of L-proline has many features in common with the A system for amino acid transport.

Functional analysis of interferon-α subtypes using monoclonal antibodies to interferon-α 4a—subtype reactivity, neutralisation of biological activities and epitope analysis

A panel of monoclonal antibodies (mAb) to a major human interferon-alpha (IFN-alpha) subtype, -alpha 4a, have been produced, characterised and used for studies of structure/function relationships of IFN-alpha subtypes. The mAb were tested for effects on receptor binding of IFN-alpha 4a, reactivity with other major subtypes -alpha 1, -alpha 2b and -alpha 14 by competitive ELISA and western immunoblotting, and for neutralisation of antiviral and antiproliferative activities of the four subtypes. The mAb could be grouped according to reactivity with IFN-alpha subtypes, group I (designated I-4-A) reacted with -alpha 4a and -alpha 2b, group II (I-4-C and I-4-F) reacted with -alpha 4a and -alpha 1, group III (I-4-D), I-4-G and I-4-H) reacted with -alpha 4a only, whereas group IV (I-4-I) reacted with -alpha 4a, -alpha 1 and -alpha 2b. No mAb reacted with IFN-alpha 14. Sequence comparisons of reactive and non-reactive IFN-alpha subtypes, and reactivity patterns with IFN-alpha fragments obtained by Lys-C digestion indicated that the epitopes were located in the N-terminal region (group I), in two regions of the middle of the molecule (group III and IV) and in the C-terminal region (group II). Binding of mAb to any of these four distinct epitopes neutralised the biological activities of IFN-alpha 4a, and in all cases, except I-4-A, inhibited receptor binding. Only the group III mAb bind to an epitope proposed to be in the vicinity of residues 30-40 which are implicated, from in vitro mutagenesis studies, in receptor binding. Binding of mAb to the other 3 epitopes neutralises biological activities by indirect mechanisms. These results emphasise the antigenic diversity between highly homologous IFN-alpha subtypes, which may have a wider functional significance. Individual mAb will have practical applications in the purification and detection of several IFN-alpha subtypes and so facilitate their further characterisation. By virtue of their different mechanisms of neutralisation, this panel of mAb will be useful in further studies of receptor interaction and signal transduction by IFN-alpha, and illustrate principles which are relevant to immunochemical studies of the receptor interactions of other cytokines.

Epithelial transport of drugs in cell culture. II: Effect of extracellular calcium concentration on the paracellular transport of drugs of different lipophilicities across monolayers of intestinal epithelial (Caco-2) cells

A human intestinal cell line, Caco-2, was used as a model to study the passive diffusion of a homologous series of drugs (beta-blocking agents) of different lipophilicity across intestinal epithelium. The permeability of the Caco-2 monolayers was modulated by the use of a calcium switch assay. The transmembrane resistance could be reversibly decreased from approximately 280 ohms.cm2 (a resistance similar to that of colon epithelium) to approximately 60 ohms.cm2 (a resistance similar to that of small intestine epithelium). Transmission electron microscopy showed that the increased electrical permeability was caused by a reversible separation of the components of the junctional complex and not by cell detachment. In general, the increased paracellular permeability resulted in a 2- to 9-fold increase in the apparent permeability coefficients for the more hydrophilic drugs (e.g., from 0.20 +/- 0.010 x 10(-6) to 1.43 +/- 0.185 x 10(-6) cm/s for atenolol), while the transport parameters for the more lipophilic drugs remained unchanged (e.g., 43.03 +/- 3.64 x 10(-6) and 46.10 +/- 3.25 x 10(-6) cm/s for propranolol). These findings indicate that it is possible to study the contribution of the paracellular pathway to the transport of drugs in the Caco-2 model.

Biochemical manifestations of a rat mammary adenocarcinoma-producing cachexia: in vivo and in vitro studies

The physical and metabolic characteristics of a Dark Agouti rat mammary adenocarcinoma and its effects on host metabolism are described. The tumour was characterized by a lack of glandular differentiation, tetraploidy, a rapid mitotic index and a high rate of glycolysis. The adenocarcinoma was readily maintained in tissue culture and could be passaged through the host by inoculating either cell suspensions or tissue explants. In the rat, tumour growth resulted in a loss of adipose tissue at a tumour mass of less than 5% body weight indicating that increased energy expenditure was already present at that stage. In addition the tumour caused anaemia, hypercalcaemia and hypoglycaemia. Hyperketonaemia was also observed in fasted tumour-bearing rats. Methotrexate arrested tumour growth in vivo. These aspects of the tumour model make it useful for investigations into host-tumour competition and mechanisms of cachexia.

Epithelial transport of drugs in cell culture. I: A model for studying the passive diffusion of drugs over intestinal absorptive (Caco-2) cells

A human intestinal cell line, Caco-2, was used as a model to study the passive diffusion of drugs across intestinal epithelium. The cells formed continuous monolayers when grown on permeable filters of polycarbonate. After 10 days in culture, the monolayers had a transmembrane resistance of approximately 260 ohms.cm2 and a cell density of 0.9 x 10(6) cells/cm2. At this time the cells were impermeable to [14C]polyethyleneglycol (MW 4000). These characteristics remained constant for 20 days (i.e., from day 10 to day 30). Six beta-blocking agents with a 2000-fold range of lipophilicity were studied for their transepithelial transport properties. The transport parameters were independent of drug concentration and transport direction. The apparent permeability coefficients ranged from 41.91 +/- 4.31 x 10(-6) cm/s for the most lipophilic drug, propranolol, to 0.203 +/- 0.004 x 10(-6) cm/s for the most hydrophilic drug, atenolol. The transport parameters were compared with those published for rat ileum. The transport rates were similar for four out of five drugs. Atenolol was transported at a slower rate in the Caco-2 model, which may be explained by the fact that the Caco-2 cells form a tighter epithelium than the rat ileal enterocytes. The findings of this paper indicate that Caco-2 cells may be used to model the intestinal absorption of drugs.

Infrequent but efficient interferon-alpha-producing human mononuclear leukocytes induced by herpes simplex virus in vitro studied by immuno-plaque and limiting dilution assays

Human blood mononuclear leukocytes (PBMCs) producing interferon-alpha (IFN-alpha) after stimulation by herpes simplex virus type 1 (HSV) in vitro were identified by a filter immuno-plaque assay. Individual IFN-alpha-producing cells (IPCs) yielded between 0.5 and 2 units IFN-alpha, sufficient to protect cultures of MDBK cells against a viral challenge. Therefore, their frequency could be determined by a limiting dilution assay as well as by an immuno-plaque assay. Similar estimates of between 2 and 55 IPCs per 10(4) PBMCs at the peak of the IFN-alpha response were obtained by the two methods. IPCs were first detected 3 h after stimulation by HSV; their number peaked at 8 h and then declined. IPC frequencies were influenced by the concentrations of HSV and PBMCs during induction, but the quantity of IFN-alpha produced per IPC was relatively constant. The relation between the numbers of IPCs and PBMCs was linear at high PBMC concentrations, whereas at low PBMC concentrations fewer IPCs than expected were detected. The response could be fully restored by adding a combination of filler cells (Namalwa or U937 cells) and conditioned medium from 6-h HSV-induced PBMC cultures. Our results suggest that HSV induces an IFN-alpha response in a relatively rare population of efficient IPCs by complex mechanisms, which may involve cell cooperation and/or production of soluble factors.

Inhibition of interleukin-2 production by tumor cell products and by CKS-17, a synthetic retroviral envelope peptide

Tumor cells of all types and species tested have been found to produce, in culture, substances that depress the expression of cell-mediated immunity, in the form of delayed-type hypersensitivity reactions in mouse feet. The factors responsible appear related immunologically to the retroviral envelope protein p15E. We have measured the effects of tumor products and conjugates of a p15E-related peptide, CKS-17, on interleukin-2 (IL-2) production by cultured, mitogen-stimulated EL4 cells; in this system IL-2 production is independent of IL-1. Supernatants of cultures of mouse, human and guinea-pig tumor cells inhibited IL-2 production in a dose-dependent fashion. CKS-17 conjugates, but not control conjugates, also inhibited IL-2 production. Responses to IL-2 of the CTLL line used were less inhibited by tumor products and very slightly inhibited by CKS-17 conjugates. IL-2 receptor density, assayed by flow cytometry, was not inhibited. IL-2 production was inhibited whether the tumor products or CKS-17 conjugates were added early or late in the course of culture of stimulated EL4 cells. Inhibition by CKS-17 conjugates was selective in that IL-2 production was inhibited to a greater degree than general protein synthesis in EL4 cells, and general protein synthesis by fibroblasts was unaffected. Measurement of IL-2 mRNA suggested that inhibition of IL-2 production was mediated post-transcriptionally. Fractionation of six different tumor supernatants on Sephacryl S-300 revealed a single peak of activity with an apparent molecular mass of 18 kDa. Antibodies to CKS-17 conjugates neutralized the inhibitory effect of native tumor products on IL-2 production. Inhibition of IL-2 production, by factors related to p15E, provides a strategically effective means of subversion of host defenses by tumors, and abrogation of this inhibition by means of antibodies might promote host resistance to tumor growth.

Suppressor factor secreted by T hybridoma established from peripheral blood lymphocytes of a bone marrow transplantation patient. I. Establishment of human T-cell hybridoma and partial characterization of suppressor factor

A stable human T-cell hybridoma was established by cell fusion between activated human peripheral blood lymphocytes from an allogeneic bone marrow transplantation patient and the JD1-17 cell line, a subclone of the human T leukemia Jurkat cell line. This hybrid clone 1-8, which bore the surface phenotype of suppressor cells (CD8+HNK1+), spontaneously secreted a factor which, at high dilutions, suppressed the responses of T and B cells induced by mitogens and alloantigens. This suppressor factor was found to be heat-resistant (56 degrees C, 30 min), stable at alkaline but not acid pH, unaffected by 2-mercaptoethanol, and sensitive to trypsin. Preparative isoelectric focusing revealed an isoelectric point of 5.35. The suppressor activity was selectively absorbed by blast T cells. By gel filtration on Sephacryl S-200 and HPLC, the suppressor activity was found in two peaks corresponding to 40-45 kDa (monomer) and 90-95 kDa (dimer).

Stimulation of glucose transport in cultured uterine cells by rat and rabbit uterine extracts

Estradiol-17 beta was previously shown to stimulate glucose transport (as measured by phosphorylation of 2-deoxyglucose) in rat uterine tissue in vivo (Meier, D.A. and Garner, C.W. (1987) Endocrinology 121, 1366-1374) but attempts to demonstrate this in uterine organ strips in vitro, in uterine tumor cell lines or in uterine cells in primary culture have been unsuccessful. However, aqueous uterine extracts and uterine luminal fluid did stimulate glucose transport in uterine tumor cells and uterine cells in primary culture. Estradiol in vivo and uterine extracts in vitro each increased the initial rate of glucose transport 1.5- to 3-fold. In each case, 2-3 h were required for the stimulation to be fully expressed. The stimulation was not inhibited by cycloheximide suggesting that protein synthesis was not required. Uteri from ovariectomized rats injected daily for 4 days with 10 micrograms estradiol contained 4-fold more activity than uteri from saline-injected control animals. The activity was acid- and heat-stable, inactivated by trypsin treatment but not removed by dextran-coated charcoal treatment, suggesting that the activity is (or is associated with) a protein. The activity eluted in the 6-12 kDa range upon chromatography on Sephadex G-50. Insulin (1-1000 ng/ml) and epidermal growth factor (1-100 ng/ml) stimulated glucose transport, but only less than 50% of the stimulation by extracts. The substance(s) present in the extracts, possibly a known growth factor, may be involved in the estradiol stimulation of glucose transport and other estradiol actions in vivo.

The elimination of mycoplasma from infected hybridomas by passaging in BALB/c mice

Hybridomas, which were found to be infected with mycoplasma, were cleared of contamination by passaging in BALB/c mice. This procedure was successfully applied to four of five cultures examined. The procedure offers a simple and effective means of eliminating mycoplasma from valuable and sometimes irreplaceable hybridoma cell cultures.

Inhibition of cell-mediated immunity by tumour cell products: depression of interleukin-2 production and responses to interleukin-2 by mouse spleen cells

Supernatants from cultures of mouse and human tumour cells inhibited the production of interleukin-2 (IL-2) by stimulated mouse spleen cells. The tumour cells tested, all of which were active, included a mouse and a human melanoma, three methylcholanthrene-induced fibrosarcomas of mice, and human HeLa cells. Supernatants from normal mouse and human fibroblasts were inactive. Inhibition was dose-dependent. Spleen cells from aged mice were more susceptible to inhibition than spleen cells from young mice. When tumour cell culture supernatants were fractionated on Sephacryl S-300, two peaks of activity were found, with apparent molecular weights of approximately 50 and 18 kD. Supernatants from tumour cell and fibroblast cultures caused variable, but generally weak, inhibition of responses of lymphoblasts to IL-2. It is suggested that inhibition of IL-2 production may be an important mode of action of tumour cell products that inhibit cell-mediated immunity.

An improved method for elimination of mycoplasmas from cell cultures

Cell lines infected by different species of mycoplasma (Mycoplasma orale, Mycoplasma hominis) were decontaminated by co-culture with human blood monocyte (BM)-derived macrophages and pooled human immunoglobulin preparations. Co-cultures with BM-derived macrophages or murine peritoneal macrophages (PM) alone were not successful. The phenotype of infected cell lines did not differ from that of uninfected cell lines as revealed by morphological, enzymecytochemical, and immunocytochemical analysis.

Macrophage stimulation with some structurally related polysaccharides

The macrophage-stimulating properties of some structurally related polysaccharides were studied in vitro. When the polysaccharides were presented to the macrophages in a sterically fixed form, i.e. as microparticles, they induced the release of interleukin 1 (IL-1) from the macrophages. Microparticulate 1.3-beta-glucan (curdlan) induced nonspecific macrophage mediated tumour cell killing while 1.4-alpha-glucan (starch), 1.6-alpha-glucan (dextran), and 1.6-alpha-mannan were without effect. The corresponding soluble polysaccharides did not stimulate the macrophages. Kinetic studies showed that although IL-1 was released immediately after stimulation, the macrophages needed a time lag of several days to develop tumour cytotoxicity. The development of cytotoxicity paralleled binding of tumour cells to the macrophages. Resident and inflammatory peritoneal macrophages showed differences in their responses to the polysaccharides. Stationary, resident peritoneal macrophages stimulated by macroparticles secreted high levels of IL-1 but expressed a low cytotoxic activity, while newly recruited inflammatory macrophages released lower levels of IL-1 but readily killed the tumour cells. The influence of cyclo-oxygenase products on the IL-1 release and macrophage cytotoxicity was also investigated. When cyclo-oxygenase was blocked with indomethacin, a significantly higher release of IL-1, and then an increased cytotoxicity, were obtained with 1.3-beta-glucan stimulated macrophages. The results suggest that microparticulate polysaccharides may be useful for studies on the induction of macrophage differentiation and also for studies on nonspecific cellular immune responses in vitro and in vivo.

A chemiluminescent assay for mycoplasmas in cell cultures

A chemiluminescent assay for the detection of mycoplasma contamination of cell cultures is described. Cells (and supernatant) derived from mycoplasma-contaminated cultures stimulate a burst of luminol-dependent chemiluminescence in cell suspensions containing phagocytic effector cell types. The assay conditions for spleen cells, human and bovine polymorphonuclear leucocytes as the responder or indicator cells have been optimized. The chemiluminescent assay can be utilized for both monolayer and suspension cell cultures and is more sensitive than colony formation on agar plates and electron microscopy. Results are obtained within 3-5 h including the time required for the preparation of the indicator cells. CL can be measured in the tritium window of standard liquid scintillation spectrometers after switching off the coincidence circuit.

Lysis of primitive teratocarcinoma cells by non-activated macrophages

The capacity of non-activated murine thioglycollate-elicited macrophages and bone marrow-derived macrophages to lyse primitive F9 teratocarcinoma cells lacking H-2 antigens was investigated. Both populations of non-activated macrophages killed F9 cells efficiently whereas they were not cytolytic against murine fibrosarcoma targets. In vitro activation by lipopolysaccharide induced the macrophages to lyse fibrosarcoma cells but did not significantly increase the level of cytolysis against F9. These results are consistent with the hypothesis that the absence of H-2 expression on target cells may serve as a signal for macrophage "foreign" recognition and cytolysis.

Elimination of mycoplasmas from cell cultures and establishment of mycoplasma-free cell lines

Several antibiotics were examined for their potential to eliminate mycoplasmas from contaminated cell cultures. Acholeplasma laidlawii, Mycoplasma arginini, Mycoplasma hyorhinis and Mycoplasma orale were effectively eliminated from experimentally contaminated mouse fibroblasts and mink epithelial cells by the use of the antibiotics minocycline and tiamutin . An elimination procedure was established, which involved the consecutive treatment of the cultures over a period of 3 weeks, followed by cell cloning. This procedure was effective when applied to cell lines which had been contaminated with unidentified and partially non-cultivable strains of mycoplasmas.

Effect of Mycoplasma pulmonis infection on protein and glycosaminoglycan synthesis of cultured connective tissue cells

Human synovial cells, fetal skin fibroblasts and rat granulation tissue fibroblasts were experimentally infected with Mycoplasma pulmonis, a species identified as a contamination of cell cultures, and studied for collagen, total protein and glycosaminoglycan synthesis. Hyaluronic acid and sulfated glycosaminoglycan synthesis were stimulated in cultures where the infection reduced cell density, while they were retarded in cultures which had proliferated into higher density than the controls. An extra polypeptide with molecular weight of 20 kD was seen in [35S]methionine-labelled cells. Media of rat granulation tissue cells showed a shift of a 39-42 kD polypeptide to 33-36 kD position in [35S]methionine and [3H]proline labellings. Other minor changes were also noticed. Collagen synthesis or procollagen conversion to collagen were, however, not altered.

Mycoplasmal infection of insect cell cultures

Twenty-five cell cultures of three insect orders from eight laboratories were tested for mycoplasmal infection. Acholeplasma laidlawii was detected in one culture, an incidence of 4.0%. A. laidlawii, Mycoplasma orale, M. arginini, but not M. hyorhinis, could establish infections of drosophila Dm-1 cell cultures at 25 degrees C. In prospective studies, drosophila Dm-1 cultures were intentionally infected with broth-propagated A. laidlawii and M. hyorhinis. M. hyorhinis did not grow and was eliminated from the Dm-1 cultures during consecutive passages. A. laidlawii grew without obvious cytopathic effects during six weekly passages; titers of over 10(7) CFU/ml were recorded at Passages 2 and 5 (p2 and p5). Minimal cell culture infectious doses were also determined during these studies. 0.1 milliliter cell samples were inoculated into Leighton tubes containing either fresh M1A culture medium or 3T6 indicator cells in McCoy's 5a medium. After 4 d of incubation at 25 and 37 degrees C, respectively, the cover slips were stained by DNA fluorochrome Hoechst 33258 (A. laidlawii) or by specific fluorescein-conjugated antiserum (M. hyorhinis). At p2 with both mycoplasma species, the procedure using M1A medium and incubation at 25 degrees C without 3T6 cells was inferior to indicator cells. In five of six experiments at least a two-log higher titer of mycoplasmas was needed to be detected with M1A and 25 degrees C. At p5 no difference could be found. Uridine phosphorylase assays of Dm-1 cultures infected with A. laidlawii, M. hyorhinis, M. orale, and M. arginini gave clearly positive results only with A. laidlawii. The ratio of incorporated uridine to incorporated uracil method yielded false positives with two drosophila cell lines. Suggestions for assay of mycoplasmas in invertebrate cell cultures are given.

Studies of cultured human T lymphocytes. I. Production of the T cell growth-promoting lymphokine interleukin-2

Described herein is a large-scale procedure that has been successfully employed for producing 62 lots (800-3000 ml) of supernatants containing the T cell growth-promoting factor Interleukin-2 (IL-2). The efficiency of these crude, unconcentrated supernatants was documented in studies in which 70 human long-term (greater than 100 days) IL-2-dependent T cell lines were established from 50 different donors. These included lines initiated from the peripheral blood of healthy subjects (N = 54), blood of children with active acute lymphoblastic leukemia (N = 6) and the thymus of children undergoing surgery to correct congenital heart defects (N = 10). The underlying concept used in constructing this method emphasizes the requirement of the monocyte-derived macrophage and its Interleukin-1 (IL-1) product to mediate IL-2 production by activated T cells. The most salient feature of this technique is the utilization of buffy coat leukocytes that had been pooled from several blood donors and sustained in spinner cultures for several days prior to polyclonal activation with phytohemagglutinin and pooled B cells of established human lymphoblastoid lines.

The genome of Plasmodium falciparum. I: DNA base composition

Some structural properties of the DNA of Plasmodium falciparum were studied thoroughly using several techniques. Its G+C content was found to be extremely low (17-19%), the lowest reported for a living organism. The DNA seems to be composed only of the four major bases as no methylated bases were detected. This DNA had a Tm value of 62.5 degrees C and its denaturation profile showed no marked intramolecular heterogeneity.