Interleukin-4 receptor expression on AIDS-associated Kaposi's sarcoma cells and their targeting by a chimeric protein comprised of circularly permuted interleukin-4 and Pseudomonas exotoxin.

BACKGROUND: AIDS-associated Kaposi's sarcoma (AIDS-KS) represents one of the most common malignancies associated with human immunodeficiency virus infection. To target effective therapeutic agents to AIDS-KS, we have identified a new target in the form of interleukin-4 receptors (IL-4R). MATERIALS AND METHODS: The expression of IL-4R on AIDS-KS cells and their subunit structure was determined by radioligand receptor binding, cross-linking and Northern and RT-PCR analyses. The in vitro effect of IL-4 and recombinant fusion protein made up of circularly permuted IL-4 and a mutated form of Pseudomonas exotoxin, IL-4(38-37)-PE38KDEL, was examined by clonogenic and protein synthesis inhibition assays. RESULTS: Five AIDS-KS cell lines expressed high-affinity IL-4R with a Kd of 23.5-219 pM. IL-4 appeared to cross-link to one major protein corresponding to 140 kDa and a broad band corresponding to 60-70 kDa. Both cross-linked proteins were immunoprecipitated with an antibody to human IL-4R beta chain. AIDS-KS cells exhibited IL-4R beta-specific mRNA. IL-4 caused a modest inhibition (31-34%) of colony formation in two AIDS-KS cell lines tested. IL-4(38-37)-PE38KDEL was found to be highly effective in inhibiting the protein synthesis in all five AIDS-KS examined. The IC50 ranged from 32 to 1225 pM. The cytotoxic action of IL-4 toxin was blocked by an excess of IL-4, exhibiting the specificity of IL-4(38-37)-PE38KDEL. The cytotoxicity of IL-4 toxin observed by a clonogenic assay corroborated well with the IC50 obtained by protein synthesis inhibition assay. Normal human endothelial cells expressed a negligible number of IL-4R (< 50 sites/cell) and were less sensitive or not sensitive to IL-4(38-37)-PE38KDEL. CONCLUSION: The presence of a new plasma membrane protein in the form of IL-4R on AIDS-KS cells may be targeted by IL-4(38-37)-PE38KDEL for its potential implication in the treatment of AIDS-KS.     

Evidence for the involvement of nitric oxide in cisplatin-induced toxicity in rats

Cisplatin treatment of rats results into a significant increase in the activity of Ca²⁺-independent nitric oxide synthase (NOS) in kidneys and liver. Significant enhancement of lipid peroxidation in gastric mucosa, kidneys and liver was also observed. The administration of N ^G-nitro-l-arginine methyl ester, an inhibitor of NOS, markedly reduced renal and gastrointestinal toxicity, and also decreased the content of blood urea nitrogen, serum creatinine, and incidence of diarrhoea along with a significant inhibition in lipid peroxidation in the target organs. The present report, while demonstrating the beneficial effect of the blockade of NO pathways during cisplatin chemotherapy, may be helpful in developing strategies for combating some of the toxic side-effects of the drug.Present address: Department of Dermatology, Case Western Reserve University, Cleveland. OH 44106. USA.     

A Secure and Robust Compressed Domain Video Steganography for Intra- and Inter-Frames Using Embedding-Based Byte Differencing (EBBD) Scheme

This paper presents a novel secure and robust steganographic technique in the compressed video domain namely embedding-based byte differencing (EBBD). Unlike most of the current video steganographic techniques which take into account only the intra frames for data embedding, the proposed EBBD technique aims to hide information in both intra and inter frames. The information is embedded into a compressed video by simultaneously manipulating the quantized AC coefficients (AC-QTCs) of luminance components of the frames during MPEG-2 encoding process. Later, during the decoding process, the embedded information can be detected and extracted completely. Furthermore, the EBBD basically deals with two security concepts: data encryption and data concealing. Hence, during the embedding process, secret data is encrypted using the simplified data encryption standard (S-DES) algorithm to provide better security to the implemented system. The security of the method lies in selecting candidate AC-QTCs within each non-overlapping 8 × 8 sub-block using a pseudo random key. Basic performance of this steganographic technique verified through experiments on various existing MPEG-2 encoded videos over a wide range of embedded payload rates. Overall, the experimental results verify the excellent performance of the proposed EBBD with a better trade-off in terms of imperceptibility and payload, as compared with previous techniques while at the same time ensuring minimal bitrate increase and negligible degradation of PSNR values.     

A model for the control of testosterone secretion

We produce here a model to explain the control of testosterone secretion. In this model the hypothalamic secretion of the hormone LHRH (luteinizing hormone releasing hormone) is controlled by a combination of local testosterone concentration and of the local concentration of the pituitary hormone LH (luteinizing hormone). Since LHRH stimulates the release of LH, and LH in turn stimulates the release of testosterone, the three hormones constitute a three-component "feedback" network. We show how this model is able to account for the pulsatility of the release of these three hormones. Furthermore, the model is consistent with results obtained from a wide range of experimental manipulations of the system. For example, it accounts for the changes observed in hormone release patterns after castration. In particular, it follows that no "neural clock", or "neural pulse-generator", is required to force the system into pulsatile behaviour.     

Electron transfer flavoprotein from Methylophilus methylotrophus: properties, comparison with other electron transfer flavoproteins, and regulation of expression by carbon source.

When grown on methylated amines as a carbon source, Methylophilus methylotrophus synthesizes an electron transfer flavoprotein (ETF) which is the natural electron acceptor of trimethylamine dehydrogenase. It is composed of two dissimilar subunits of 38,000 and 42,000 daltons and 1 mol of flavin adenine dinucleotide. It was reduced by trimethylamine dehydrogenase to a stable anionic semiquinone form, which could not be converted, either enzymatically or chemically, to the fully reduced dihydroquinone. This ETF exhibited spectral properties which were nearly identical to ETFs from bacterium W3A1, Paracoccus denitrificans, and pig liver mitochondria. M. methylotrophus ETF cross-reacted immunologically and enzymatically with the ETF of bacterium W3A1 but not with the other two ETFs. In M. methylotrophus and bacterium W3A1, ETF and trimethylamine dehydrogenase were each expressed during growth on trimethylamine and were each absent during growth on methanol.     

Electron transfer flavoprotein from pig liver mitochondria. A simple purification and re-evaluation of some of the molecular properties.

Electron transfer flavoprotein (ETF) from pig liver mitochondria has been purified to homogeneity by a three-step procedure with approx. 10-fold higher yields than previously reported. The purified ETF exhibits an absorption coefficient for the bound FAD of 13.5 mM-1.cm-1 at 436 nm and an isoelectric point of 6.75. Gel filtration, sodium dodecyl sulphate gel electrophoresis and flavin analysis indicate that pig liver ETF is a dimer, composed of non-identical subunits (Mr 38 000 and 32 000) with only one FAD/dimer. Anaerobic reduction by dithionite produces anionic flavin semiquinone as a stable intermediate and establishes the flavin to be the only redox-active chromophore in ETF.