Biomedical subjects
Publications and source records attributed to V G Budker.
In the present work it is shown that large unilamellar lecithin/cholesterol liposomes are able to sequester small negatively charged liposomes in the presence of divalent cations. Evidence is presented suggesting that the sequestration occurs via the formation of membrane invaginations transformed further into intraliposomal vesicles.
The outer surface of isolated metaphase chromosomes has been investigated by a method of thermally activated tritium labelling. We show that both chromosomal proteins and DNA are tritium-labelled. Fractionation of the chromosomal proteins reveals that scaffold proteins are the most labelled in condensed and EDTA-decondensed chromosomes. Exposition of some scaffold proteins on the outer surface of metaphase chromosomes is suggested.
During experimental CCl4 cirrhosis, an increase of membrane-associated factor stimulating 3T3 cell proliferation in vitro was observed. This stimulator is a 150-kD protein similar to one previously described. In situ perfusion released growth stimulatory activity, suggesting a peripheral plasma membrane protein localizing on basolateral surfaces. The activity increased with increasing number of CCl4 treatments, reaching a maximum at the 14th intoxication. It was faster than the proliferation of connective tissues determined histologically. Cessation of treatment caused a decrease in activity to that of the level of untreated liver, although the number of fibroblastlike cells remained large. This data, taken with the results of experiments with enriched hepatocyte fraction, may serve as an evidence in favor of hepatocyte origin of the factor. A factor inhibiting fibroblast proliferation was measured in detergent extracts from membranes, suggesting an integral membrane protein. The activity of the inhibitory factor increased in acute liver lesions, but at the stage of maximal fibrogenesis this factor is reduced to levels comparable to those of the intact liver. Therefore it is unlikely that this factor is involved in CCl4-induced fibrogenesis at the final stages. These factors may be common controls for various hepatic lesions causing fibrosis, both in clinical and experimental modeling.
The results of studies on interaction of oligonucleotides and polynucleotides with cell membranes are reviewed. Oligonucleotides and polynucleotides bind to lipid membranes in the presence of divalent cations that may result in spontaneous encapsulation of nucleic acids and transfer of the formed vesicles to the other side of the membrane. Oligonucleotides can enter eukaryotic cells and interact with cellular RNA and DNA. On the surface of eukaryotic cells, there are proteins capable of binding to nucleic acids that may be involved in oligonucleotide uptake. Oligonucleotides bind to cellular CD4 receptors. Efficient delivery into cells can be achieved by conjugation of oligonucleotides to lipophilic groups or by encapsulation into membrane carriers.
Isolated mitotic chromosomes are able to form complexes with phosphatidylcholine liposomes in the presence and absence of Ca2+ ions, in the latter case in the presence of polyamines. Interactions with chromosomes stimulates liposome fusion. The fusion is promoted by condensed and EDTA-decondensed chromosomes.
In the course of experimental CCl4-induced cirrhosis, an increase of the membrane-associated factor stimulating 3T3 cells' proliferation in vitro was observed. Gel filtration showed an approximate molecular mass of 150 kDa. Extraction of growth stimulatory activity by liver perfusion in situ demonstrated a peripheral plasma membrane protein localization. The activity increased with an increasing number of CCl4 treatments, reaching a maximum at the tenth intoxication, faster than the proliferation of connective tissues. Cessation of treatment caused a decrease in activity to the level of untreated liver, although the amount of fibroblast-like cells remained large, which is evidence in favour of an hepatocyte origin of the factor.
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High molecular mass DNA was efficiently taken up by large unilamellar vesicles exposed to a short pulse of electric field (0.1-1 ms) with an intensity as high as 12.5 kV/cm. The efficiency of uptake increased significantly in presence of Mg2+ ions and was approximately 0.6 and 1.5 micrograms of DNA per mumol of lipid for T7 DNA and plasmid pBR 322, respectively. The results presented indicate that DNA was taken up as a result of the electrostimulated formation of endosome-like vesicles rather than via field-induced membrane pores.
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A/HeJ mice with experimental metastases of HA-1 tumor in the liver and other organs were given therapeutic doses of cisplatin, free or encapsulated in phosphatidylcholine cholesterol freeze-thawed liposomes, intravenously. Free cisplatin treatment was found to decrease the growth rate of liver metastases by half and to extend survival by 1.5 times as compared to controls. The inhibitory effect of liposome-encapsulated cisplatin on hepatic metastases growth was more pronounced than that of the free drug although it weakly affected metastatic growth in other organs.
Cells of lines of mice transplantable tumours metastasizing into the lung have been used: lung adenocarcinoma (AL), Lewis lung carcinoma (LL), melanoma B-16 (B-16), mammary tumour MMT-1 (MMT-1), malignant subline of L-cells (LS). Hybrid vesicles were obtained for each tumour. They contain fragments of cell plasmatic membranes (PM). It has been shown that AL-, LL-, LS- and B-16-liposomes were accumulated in lung, the trapping of AL- and LL-liposomes being higher than that of the other hybrid vesicles. Despite the similar dynamics and frequency of metastatic spreading into the lung for all tumours studied, no trapping of MMT-1-vesicles in the target-organ was observed. The role of specific interaction of tumour cells PM with the endothelium of the lung capillaries in the process of organotropic metastatic spreading is discussed.
The model of experimental metastases in the HA-1 tumour in the liver of A/He mice was used to show that the anti-tumoural effect of cis-dichlorodiamminoplatinum being used in the liposomes increases, while that of vinblastine (VB) decreases. It is suggested that the low activity of liposome-encapsulated VB as to its influence on the tumour growth in the liver is a result of preferable uptake of liposomes by Kupffer cells and hepatocytes from where VB cannot diffuse into tumour cells since it binds to intracellular tubulin.
The kinetic characteristics of the main isozymes of Drosophila virilis esterase were studied and Km values of esterase-2, -4, and -6 and p-esterase for alpha- and beta-naphthyl acetate were obtained. Juvenile hormone (JH) was shown to inhibit the p-esterase activity when in competition with beta-naphthyl acetate and the general esterase inhibitor, diisopropylphosphofluoridate (DFP), was shown to inhibit all the components of the D. virilis esterase patterns except p-esterase. While studying the changes of p-esterase activity in D. virilis ontogenesis, the increase in p-esterase activity in the wandering larvae, prepupae, and early pupae was found to correlate with a decrease in JH titer at these stages. The decrease in JH level in a temperature-sensitive lethal mutant larvae of D. virilis at high temperatures was shown to correlate with increased p-esterase activity. These results confirm that p-esterase of D. virilis is JH-esterase.
Cleavage of phage lambda DNA by restriction endonucleases in the presence of model phosphatidylcholine membranes was studied. Bsp1, Pst1 and Bam H1 were found to cleave DNA under these conditions to a considerably decreased extent. This effect does not result from irreversible inactivation of the enzymes or their direct interaction with the membranes. The most probable explanation of the membrane inhibitory effect is the change of DNA substrate properties resulting from its Mg2+-mediated binding to the membranes.
A method for gene transfer by means of interphase nuclei encapsulated within lipid membranes was developed. The method was based on passage of interphase nuclei through a layer of organic solvents containing phospholipids. Evidence was obtained indicating that the nuclei become surrounded by a protective phospholipid membrane: measurements of bound labelled or non-labelled phospholipids; decrease in the permeability of lipid-encapsulated nuclei for high molecular compounds; visualization by direct electron microscopy. Lipid-encapsulated nuclei of mink fibroblasts were used for transformation of mutant mouse LMTK- cells (deficient for thymidine kinase). The frequency of occurrence of HAT-resistant colonies/recipient cell was 1.9 X 10(-5). Biochemical analysis of 14 independent clones demonstrated that they all contained TK1 of mink origin. Analysis of 15 other biochemical markers located on 12 of the mink chromosomes revealed the activities of mink galactokinase (a syntenic marker) in 5 transformed clones, and that of mink aconitase-1 (the marker of mink chromosome 12) in 1 clone. No cytogenetically visible donor chromosomes were identified in the transformed clones. Nine transformed clones were tested for the stability of the TK+ phenotype; of these, the phenotype was expressed stably in 3 and unstably in 6. The method suggested is similar to the gene transfer procedure using total DNA. Its advantage is in ensuring efficient gene transfer and donor DNA integrity.
In the present paper the interaction of metaphase chromosomes and chromatin with model and natural lipid membranes was studied. It was shown that chromatin and chromosomes are able to form complexes with membranes in the presence of divalent cations. In such complexes, the typical structure of chromosomes is altered. The character of this alteration in chromosomal structure was investigated with the use of electron microscopy and chemical modification with dimethylsulphate (DMS). The latter is possible because, according to the presented data, the condensation of chromatin into chromosomes is associated with a decrease in accessibility of N-3 in adenine (the protection of the minor groove of DNA) to modifications, and with an increased methylation of N-1 in adenine (the disarrangement of the secondary structure of DNA). It was shown that the interaction of chromosomes with liposomes provides various levels of unfolding up to the appearance of chromatin-like structures. The secondary DNA structure of decondensed chromosomes coincides with the secondary structure of chromosomal but not chromatin DNA, whereas the extent of shielding of the minor groove of DNA in such decondensed structures typical for chromatin DNA. It is possible to suggest that the chromosomal decondensation in telophase of mitosis is initiated by the action of a membrane component of the developing nuclear envelope.
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A new method of the coating of isolated cell nuclei with additional phosphatidylcholine membranes is described. The additional membrane was visualized under the electron microscope using ferritin as a label. The coating diminished leakage of the content of the nuclei and restricted permeability of the nuclei for exterior macromolecules.