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A randomly alkylated copolymer of N-isopropylacrylamide, methacrylic acid and N-vinyl-2-pyrrolidone was characterized with regard to its pH- and temperature-triggered conformational change. It was then complexed to liposomes to produce pH-responsive vesicles. Light scattering and differential scanning calorimetry experiments performed at neutral pH revealed that the polymer underwent coil-to-globule phase transition over a wide range of temperatures. At 37 degrees C and pH 7.4, although the polymer was water-soluble, Fourier transform infrared spectroscopy analysis showed that it was partly dehydrated. At acidic pH, the decrease in the lower critical solution temperature was accompanied by an increase in cooperativity degree of the phase transition. Complexation of copolymer to liposomes did not substantially influence its phase transition. The liposome/copolymer complexes were stable at neutral pH but rapidly released their contents under acidic conditions. The copolymer slightly increased liposome circulation time following intravenous administration to rats. The addition of poly(ethylene glycol) to the formulation had a detrimental effect on pH-sensitivity but enhanced substantially the circulation time.

We have previously localized an antigen of oviductal origin in the zona pellucida of superovulated hamster ova. This antigen is a high-molecular-weight glycoprotein that is secreted by the nonciliated secretory cells of the oviduct and later is transferred to the zona pellucida of the oocyte during oviductal transit. This glycoprotein is rich in N-acetyl-D-galactosamine residues and has been designated Hamster Oviductin-1. In the present study, we have examined the intracellular localization of the oviductin in the blastomeres of developing embryos of the golden hamster. Seventeen cycling females were used for the localization and detection of the oviductin in oviductal oocytes and early embryos. Thin sections of hamster 1-cell oocytes, and 2-cell, and 8-cell embryos, embedded in Lowicryl and then incubated with the monoclonal antibody against the oviductin, revealed a homogenous distribution of antigenic sites in the matrix of the zona pellucida. While immunogold labeling was completely absent in the cytoplasm of 1-cell ova prior to fertilization, labeling was found associated with coated pits and coated vesicles and with flocculent material in the perivitelline space of fertilized eggs. In addition to these labeled endocytic structures, many endosomes, multivesicular bodies, and secondary lysosomes were also found to be labeled heavily in the cytoplasm of developing embryos. Our results indicate that following the transfer of Hamster Oviductin-1 to the zona pellucida of oocytes during transit in the oviduct and subsequent to fertilization, some of the oviductin associated with the zona pellucida appears to be internalized by blastomeres of the embryo and further processed through the endosomal/lysosomal pathway.

Background: EGF-induced activation of mTORC1 in hepatocytes is essential for cell proliferation. Results: Blocking EGF-induced vacuolar acidification reduced intracellular essential amino acid levels and inhibited mTORC1 signaling without affecting Akt/Erk activation. Conclusion: EGF-induced mTORC1 signaling depends on sustaining intracellular amino acid levels. Significance: Our results support a role for vacuolar acidification in growth factor signaling.

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