Natural occurrence of aflatoxin B<Subscript>1</Subscript> in some Indonesian food and feed products in Yogyakarta in year 1998–1999

A survey was conducted between 1998–1999 to evaluate the level of aflatoxin B₁ (AfB₁) contamination in some selected Indonesian food products, mainly peanuts and peanut products for sale in supermarkets or traditional markets in Yogyakarta, Indonesia. Quantitative analysis was carried out on 118 samples using the ELISA (Enzyme-Linked Immunosorbent Assay) technique. The results indicate that (61.1%) samples were contaminated with AfB₁ at range 2.0 to 249.0 μg/kg. Approximately 50% of the baby food products analysed were contaminated with AfB₁ and the maximum level found was 7.0 μg/kg. In corn products and fermented products, AfB₁ was detected in 66.7 and 50.0% of samples, respectively. A level as high as 5.6 μg/kg of AfB₁ was found in the corn and 6.0 μg/kg in fermented product. AfB₁ was also detected in all rice products, feed products, and other processed products at levels of up to 7.0, 27.0, and 26.0 μg/kg, respectively.     

The role of β2-glycoprotein I in liposome-hepatocyte interaction

Adsorption of serum proteins to the liposomal surface plays a critical role in liposome clearance from the blood. The aim of this study was to investigate the role of liposome-adsorbed serum proteins in the interaction of liposomes with hepatocytes. We analyzed the serum proteins adsorbing to the surface of differently composed small unilamellar liposomes during incubation with human or rat serum, and found that one protein, with a molecular weight of around 55 kDa, adsorbed in a large amount to negatively charged liposomes containing phosphatidylserine (PS) or phosphatidylglycerol (PG). The binding was dependent on the liposomal charge density. The ∼55-kDa protein was identified as β₂-glycoprotein I (β₂GPI) by Western blotting. Despite the high affinity of β₂GPI for strongly negatively charged liposomes, in vitro uptake and binding experiments with isolated rat hepatocytes, Kupffer cells or liver endothelial cells, and with HepG2 cells showed no enhancing effect of this protein on the association of negatively charged liposomes with any of these cells. On the contrary, an inhibitory effect was observed. We conclude that despite abundant adsorption to negatively charged liposomes, β₂GP1 inhibits, rather than enhances, liposome uptake by liver cells.     

cytophotometric,flow cytofluorometric and morphometric demonstration of the existence of an antigen dependent thymus lymphocyte subpopulation

Summary Using absorption cytophotometry and flow cytofluorometrical DNA and protein estimation of single thymus lymphocytes we were able to establish that after injection of a large dose of antigen (ovalbumin) a subpopulation of lymphocytes arises in the thymus with high protein contents above that of those lymphocytes normally present, however, in small quantities in the thymus. By morphometrical analysis it was established that these lymphocytes are situated in the outermost cortex.     

Histochemical staining of cadmium thiolate clusters in livers of rats treated chronically with cadmium

In livers of rats exposed to varying doses of CdCl2 80-90% of the cadmium content present in the fresh tissue is retained if these livers are fixed with a neutral or acid formalin fixative. Cadmium assays during different stages of the staining procedure for protein bound disulphides show the ability of this staining to demonstrate cadmium thiolate clusters next to disulphides. The methods described may also be useful in gaining more insight in the mechanism involved in fixation and staining procedure of some other metals.     

Fusion of influenza virus in an intracellular acidic compartment measured by fluorescence dequenching

The fusion of influenza virus with cultured cells has been investigated. The virus was labelled with the fluorescent probe octadecyl rhodamine B and fusion was monitored as fluorescence dequenching due to dilution of the probe from the viral into a cellular target membrane. Fusion with the plasma membrane does not occur, unless the extracellular pH is temporarily lowered. At neutral pH fusion occurs only after a lag phase of 10-15 min, the time required for virus internalization, and the reaction is inhibited by NH4Cl, indicating that it takes place in an intracellular acidic compartment, most likely the endosome. This suggests that influenza virus infects cells via the endocytic pathway.     

Persistent directional cell migration requires ion transport proteins as direction sensors and membrane potential differences in order to maintain directedness

Background  

Ion transport proteins generate small electric fields that can induce directional cell motility; however, little is known about their mechanisms that lead to directedness. We investigated Na, K-ATPase (NaKA) and Na+/H+ exchanger isoforms (NHE1 and 3) in SaOS-2 and Calvarial osteoblasts, which present anode- and cathode- directed motility, during electrotaxis.     

Quantitative immunohistochemistry of metallothionein in rat placenta

The presence of metallothionein (MT) was demonstrated in placentae from cadmium-exposed and control rats by an immunohistochemical technique, using peroxidase as label and the diaminobenzidine procedure for the staining reaction. The protein was found in different regions of the placenta, i.e. in trophoblastic labyrinth, in spongiotrophoblast and in visceral yolk sac. Cytophotometric analysis of the final reaction product revealed that the amount of MT was increased in the placental labyrinth of cadmium-exposed rats. Increases were found in both nuclei and cytoplasm of trophoblast cells in the labyrinth region. Possible roles of MT in the transport of zinc and in the carbohydrate metabolism are discussed.     

Histochemical staining of cadmium thiolate clusters in livers of rats treated chronically with cadmium

Summary In livers of rats exposed to varying doses of CdCl₂ 80–90% of the cadmium content present in the fresh tissue is retained if these livers are fixed with a neutral or acid formalin fixative.Cadmium assays during different stages of the staining procedure for protein bound disulphides show the ability of this staining to demonstrate cadmium thiolate clusters next to disulphides. The methods described may also be useful in gaining more insight in the mechanism involved in fixation and staining procedure of some other metals.