In vitro assays for the developmental toxicity of xenobiotic compounds using differentiating embryonal carcinoma cells in culture.

Murine embryonal carcinoma (EC) cells, which resemble the undifferentiated cells of the epiblast in the blastocyst, were used to establish two in vitro assays for developmental toxicants. The target processes in the assays are the differentiation of EC cells into endodermal and mesodermal derivatives, respectively. These processes were selected because they are crucial and specific for embryogenesis, and also because EC cell differentiation has been shown to be sensitive to various compounds that are teratogenic in vivo.

Benzodiazepines preferentially affect mesolimbic dopamine turnover in rats.

Withdrawal of benzodiazepines in man may induce hallucinatory symptoms and can evoke delusional depressions, which can be treated with dopamine-antagonistic drugs. Withdrawal of benzodiazepines in rats induces a strong hyperactivity during daytime, leaving the nighttime activity relatively undisturbed. This hyperactivity may be related to an enhanced dopaminergic activity in the mesolimbic area, especially in the nucleus accumbens.

Instability of a hybridoma cell line in a homogeneous continuous perfusion culture system.

In this study several analytical techniques were applied to obtain information about the stability of expression, the yield, and the integrity of a monoclonal antibody (Mab) produced by hybridoma cell line RIV6 in a homogeneous continuous perfusion culture system. The total antibody as well as the isotype-specific antibody contents decreased continuously during the course of cultivation, while the viable cell concentration remained constant. The origin of the discrepancy between the Mab contents observed by two enzyme-linked immuno sorbent assay (ELISA) systems during the steady state was due to fragmentation of the IgG molecule, either cytoplasmic or in the culture fluid, as determined by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting.

Strengthening the Montreal protocol: does it cool down the greenhouse?

Strengthening of the Montreal Protocol is recently being negotiated in London in 1990 in order to achieve further reductions of the regulated CFCs and to include possibly more substances. In this article the implications of different policies with respect to control of ozone depleting substances for climate change are analysed, including the proposed substitution by HCFCs and HFCs, carbon tetrachloride and methylchloroform. A special halocarbon module was developed within the framework of RIVM's Integrated Model to Assess the Greenhouse Effect (IMAGE).

A statistical approach to the regional use of critical loads.

The premise of this paper is that: (1) effects of spatial heterogeneity of watershed response to acid deposition must be considered when models are used to set abatement policies, and (2) the evaluation of critical chemical values is a better measure off the effects of abatement policies than the comparison of deposition values to critical loads. The authors used Monte Carlo methods to apply a site-specific version of the RAINS-Lake-Model to a regional data set from The Netherlands. Statistical methods were then used to identify the important parameters affecting the spatial and temporal response, i.

Chronic infusion of clonidine does not alleviate spontaneous morphine withdrawal symptoms in rats.

Opiate withdrawal is associated with behavioural symptoms and a sympathetic hyperactivity, the latter being sensitive to clonidine. The central question is whether behavioural symptoms would be also sensitive to clonidine. A rat model was used in which the locomotor activity was measured 24 h a day during the morphine withdrawal phase.

An isotype-specific spot-ELISA for the enumeration of antibody-secreting hybridomas and the determination of isotype switch variants.

A solid-phase spot enzyme-linked immunosorbent assay (spot-ELISA) using rat monoclonal antibodies (MAbs) and an image-processing system is described. This isotype-specific spot-ELISA permits the enumeration of antibody-secreting cells irrespective of the specificity of the secreted antibodies. When used in combination with an ELISA, the antibody production per cell can also be evaluated.

Biotransformation of cyclophosphamide in post-implantation rat embryo culture using maternal hepatocytes in co-culture.

The post-implantation rat embryo culture technique is employed to study embryotoxic effects of xenobiotic compounds in the absence of the maternal compartment. For compounds biotransformed in vivo the embryo culture technique must be adapted in order to mimick the in vivo effects. In the present study the possibility of co-culturing metabolically active maternal hepatocytes suspended in the standard culture system with rat serum as a medium was investigated.

Successful approach for detection of low numbers of enterotoxigenic Escherichia coli in minced meat by using the polymerase chain reaction.

The polymerase chain reaction (PCR) was used as a tool for the detection of enterotoxigenic Escherichia coli in minced meat. With two synthetic 29-mer oligonucleotides, a 195-bp fragment from the E. coli heat-labile enterotoxin (LT) gene could be amplified specifically.

On the structure of immune-stimulating saponin-lipid complexes (iscoms).

Immune-stimulating complexes (iscoms) are stable complexes of cholesterol, phospholipid and Quil A, a triterpene saponin mixture in the size range from 40 to 100 nm. They can be used as antigen carriers in subunit vaccines. In this paper it is demonstrated that iscoms are rigid, negatively charged vesicles in which small water soluble molecules like carboxyfluorescein cannot be retained.

Monoclonal antibodies against the 70-kilodalton iron-regulated protein of Neisseria meningitidis are bactericidal and strain specific.

When grown under iron limitation, Neisseria meningitidis expresses a number of outer membrane proteins (OMPs), one of which is a 70-kilodalton (kDa) major OMP. After immunization of mice with outer membrane preparations of iron-depleted cells of strain H44/76 (B:15:P1.7,16), hybridoma cell lines producing monoclonal antibodies against the 70-kDa OMP were obtained.

Survival of Mycoplasma hyorhinis in trypsin solutions.

The survival of four strains of Mycoplasma hyorhinis in stock solutions of trypsin was tested at 22, 4 and -15 degrees C. Low (10(4)-10(5) cfu/ml) and high (10(6)-10(7) cfu/ml) initial concentrations of each strain were used, each was tested three times. A regular decrease of low and high concentrations (1 log in 10 and 20 min, respectively) was seen at 22 degrees C.

New developments in the cultivation of hybridoma cells in homogeneous continuous perfusion systems.

Monoclonal antibodies (MCA) are of great value both for in vitro and in vivo diagnostic and for therapeutic application. For in vitro application relatively small amounts of antibody are required. The therapeutic application, however, requires larger quantities.

Characterization of antibody labelled colloidal gold particles and their applicability in a sol particle immuno assay (SPIA).

This study describes the characterization of antibody labelled colloidal gold particles and their applicability in a sol particle immuno assay (SPIA) to quantify murine monoclonal antibodies of all IgG isotypes. Two physical methods (transmission electron microscopy (TEM) and dynamic light scattering (DLS], were used to obtain information about particle size and morphology of the gold sols, but only with DLS antibody labelling could be detected. In addition, electrophoretic methods like agarose electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed also that antibody labelling was successful.

Purification, cyanogen bromide cleavage, and amino terminus sequencing of class 1 and class 3 outer membrane proteins of meningococci.

Meningococcal class 1 and 3 outer membrane proteins (OMPs) were subjected to cyanogen bromide treatment. The class 3 OMP was found to be resistant to cyanogen bromide, while the class 1 OMP was cut into two main fragments of 25 and 17 kilodaltons. The N-terminal sequences were determined for class 1 and class 3 proteins, which exhibit similarities to one another and to OMP I of gonococci.

Definition of meningococcal class 1 OMP subtyping antigens by monoclonal antibodies.

The subtypes of meningococci are defined by antigenic determinants on the class 1 outer membrane proteins. The established subtypes, designated by P1 and a number according to the prototype reference strain on which they were first recognized by monoclonal antibodies, includes P1.2, P1.

Immunogenicity of liposomes and iscoms containing the major outer membrane protein of Neisseria gonorrhoeae: influence of protein content and liposomal bilayer composition.

The influences of Neisseria gonorrhoeae protein IB content and bilayer composition of liposomes and protein content of iscoms on immunogenicity were investigated. Changes in the protein content of liposomes did not influence the immunoglobulin G response, whereas the response was lowered when the amount of protein in iscoms was increased. Bilayer composition only influenced the primary immunoglobulin G response; immunological memory was not affected.