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Biomedical subjects

V G Budker

Publications and source records attributed to V G Budker.

At least 37 records · Page 2Linked to original sources
PubMed1986

[Cleavage of DNA adsorbed on the surface of phospholipid membranes by restrictases type II].

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.

Adsorption↗
PubMed1985

Transfer of mink genes into mouse cells by means of isolated lipid-encapsulated nuclei.

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.

Animals↗
PubMed1985

Membrane-mediated changes in the structure of chromosomes.

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.

Adenosine Triphosphate↗
PubMed1985

[New method of encapsulating isolated nuclei into a lipid membrane].

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.

Animals↗
PubMed1985

[Fluorescence of Tb3 complexes with metaphase chromosomes of mink fibroblasts].

The fluorescence of the Tb3+ complex with metaphase chromosomes of mink fibroblasts was studied. It was shown that the fluorescence intensity of this complex is 6.5 times as high as that of the Tb3+-native DNA complex. The fluorescence of the chromosome-Tb3+ complex is predominantly determined by chromosomal DNA. The high intensity of fluorescence may be due to partial disturbances in the secondary structure of DNA during folding of the metaphasic chromosome.

Animals↗
PubMed1984

Inhibition of tumor growth in mice treated with synthetic muramyl dipeptide.

Treatment with synthetic MDP inhibited growth of transplantable, chemically induced tumors in syngeneic mice. The tumor-inhibitory effect was dependent on the schedule of MDP administration. Growth of SC transplants of a nonmetastasizing, MC-induced fibrosarcoma, MC11, was inhibited by local treatment with 200 micrograms and 1,000 micrograms MDP given SC 5-7 weeks before challenge. Treatment with lower (10 micrograms and 100 micrograms) doses of MDP and shorter (1-4 weeks) time intervals was not effective. Single doses of MDP (10-1,000 micrograms) 1-3 weeks after challenge had no effect. Growth of IV-inoculated, metastasizing AAT-induced hepatoma A was inhibited by IV injections of 20 micrograms MDP given 1 and 2 days prior to the challenge. Significant increases in the survival of hepatoma-bearing mice were observed only after injections of MDP incorporated in multilamellar liposomes.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1984

[Electron microscopic analysis of the structure of metaphase chromosomes after liposome treatment].

The fine structure of the methaphase chromosomes from the Chinese hamster cell culture was studied after the incubation with lyposomes isolated from hen egg yolk phosphatidilcholine, or from the total rat liver phospholipid. It has been found that during incubation lyposomes surround chromosomes, form a multifold covering considerably decondensing the chromosome matrix. The data obtained indicate that the analogues of cell membrane - lyposomes - may be involved in the regulation of the structural organization of metaphase chromosomes.

Animals↗
PubMed1983

Structure of DNA in metaphase chromosomes of mouse fibroblasts.

We show that N-1 in adenine of chromosomal DNA is methylated by treatment of metaphase chromosomes with dimethylsulphate while this is not the case in chromatin. The data on methylation are consistent with those obtained from the experiments with S1-nuclease treatment of chromatin and chromosomes. This suggests a disarrangement of DNA secondary structure in the metaphase chromosomes.

Animals↗
PubMed1982

Adsorption of non-membrane proteins on the surface of model phospholipid membranes.

1. Two new methods are proposed for enhancement of the binding of hydrophilic proteins by liposomes. 2. An alkylating derivative of phosphatidic acid has been obtained by its reaction with N,N,N'-tris(2-chloroethyl)-N'-(p-formylphenyl)propylene-1,3-diamine. The alkylating activity of this derivative is very low due to the electron-acceptor effect of the formyl residue. Phosphatidylcholine liposomes which contain this alkylating derivative in the lipid bilayer may be obtained. The compound residing in the outer monolayer may be reduced by NaBH4. Upon reduction, the formyl residue is transformed into a hydroxymethyl residue. Therefore, the alkylating group of the compound is activated, and proteins may be attached covalently to the outer monolayer by alkylation with such chemically reactive liposomes. 3. Reaction of alkylating liposomes with myoglobin results in covalent binding of this hydrophilic protein. Complement-mediated leakage of such myoglobin-carrying liposomes may be induced by antibodies against myoglobin. 4. Modification of hydrophilic proteins with dansyl chloride results, even at small extents of modification, in a dramatic increase of the affinity of such proteins to phosphatidylcholine liposomes.

Adsorption↗
PubMed1982

Subcutaneously injected radiolabeled liposomes: transport to the lymph nodes in mice.

Male A/He mice were given sc injections in the feet with [3,5,3'-125I]triiodothyronine, [125I]T3, either in the free state or encapsulated within sonicated phosphatidylcholine liposomes. Radioactivity was recovered from the injection site, the popliteal lymph nodes (LN), blood, liver, lungs, and spleen at various times (5 min to 6 hr) after injection. The highest level of radioactivity was found in the popliteal LN of mice given liposome-encapsulated (LE) [125I]T3: For more than 3 hours after the injection, radioactivity was fivefold to fiftyfold higher there than that in all the other organs including the popliteal LN of mice given injections of free [125I]T3. The results demonstrated that sc injected liposomes enter the lymphatic pathways and reach the draining LN. Thus local administration of LE antitumor drugs into the sites of a malignant tumor before its excision might be useful in preventing postoperative metastases to the draining LN.

Animals↗
PubMed1981

Intralymphatic administration of liposome-encapsulated drugs to mice: possibility for suppression of the growth of tumor metastases in the lymph nodes.

The antimetastatic effects of two drugs, cis-diamminedichloroplatinum(II) (DDP) and hydrocortisone (liposome-incorporated or free), were studied. The experimental models were regional and distant metastases of hepatoma A and pulmonary adenocarcinoma, which were transplanted into the footpads of A/He mice. Liposomes were prepared from phosphatidylcholine by sonic dispersion. DDP and hydrocortisone were injected sc into the region of the plantar aponeurosis of the foot with the primary tumor. This administration route was considered to be equivalent to the intralymphatic route. Evidence indicated that only liposome-incorporated DDP and hydrocortisone decreased significantly the frequency and growth rate of tumor metastases in the regional lymph nodes. The effect observed was not due to the direct action of the drugs on the primary tumors. When nonencapsulated, these drugs were ineffective. Both liposome-encapsulated and free DDP did not affect distant metastases of pulmonary adenocarcinoma. The intralymphatic administration of liposome-encapsulated antitumor agents is suggested as a method for the prophylactic treatment of tumor metastases in the lymph nodes.

Animals↗
PubMed1980

Interaction of polynucleotides with natural and model membranes.

Polynucleotides adsorb on natural and model phospholipid membranes in the presence of Mg2+-cations. Adsorption of nucleic acids on membranes results in a considerable change of their secondary structure. The presence of model phosphatidylcholine membranes greatly stimulates the rate of the synthesis of RNA by E. coli RNA-polymerase on DNA template.

Animals↗