Effect of ion adsorption on the electrokinetic properties of erythrocytes

The microelectrophoresis technique was used to determine the dependence of human erythrocyte surface potential on the concentration of various cations and anions. The interpretation of the results is based on the Gouy--Chapman--Stern theory. Values of pK, characterizing the binding of ions to the external surface of erythrocytes, as well as numbers of binding sites per unit area were determined. The affinities of ions for the red cell membrane were shown to decrease in the sequence: H+ greater than Ca2+ greater than Sr2+ greater than Mg2+ greater than Ba2+ greater than Li+ greater than Na+ congruent to congruent to K+ congruent to NH4+ and trinitrophenol greater than IO4- greater than CIO4- greater than salicylate congruent to I- greater than greater than SCN- greater than H2PO4- greater than Br- greater than Cl- greater than HPO4(2-). Changes in the ionic strength of the medium resulted in changes in numbers of exposed ion-binding sites. This phenomenon is interpreted in terms of ionic strength-dependent structural transformations of the cell surface coat.     

Cytogenetic changes in the Namalwa cell line of human malignant lymphoma induced by inhibitors of DNA replication and synthesis

Namalwa cells originating from the malignant human lymphoma have been analyzed cytogenetically upon short-time exposure to subtoxic doses of inhibitors of DNA replication and synthesis, either etoposide or fludarabine. The intact cells were characterized by the modal class of the chromosomes within the diploid range with the proportion of the aberrant cells amounting to 16.0 +/- 0.5%. Upon exposure to etoposide the percentage of the aberrant cells increased amounting to 26.1 +/- 2.9 through 39.8 +/- 1.7% depending on the duration of the exposure and the dose of the drug. At the same time the number of the polyploid cells increased but the modal class retained within the diploid range. Upon exposure to fludarabine the percentage of the cells with the aberrant chromosomes increased to 57.1 +/- 2.9%. Two modal classes appeared--the first approaching the diploid number and the second being polyploid. The exposure to either etoposide or fludarabine resulted in increasing number of the chromatide aberrations with more frequent involvement of #1, #2, #5, #6, #7, #11, #13, #14, #16 and #17 chromosomes. The data obtained have shown the susceptibility of Namalwa cells to the subtoxic concentrations of the inhibitors of DNA synthesis and replication used in the study resulting in the survival of the novel clones resistant to the drugs.     

Golgi enzymes are enriched in perforated zones of golgi cisternae but are depleted in COPI vesicles

In the most widely accepted version of the cisternal maturation/progression model of intra-Golgi transport, the polarity of the Golgi complex is maintained by retrograde transport of Golgi enzymes in COPI-coated vesicles. By analyzing enzyme localization in relation to the three-dimensional ultrastructure of the Golgi complex, we now observe that Golgi enzymes are depleted in COPI-coated buds and 50- to 60-nm COPI-dependent vesicles in a variety of different cell types. Instead, we find that Golgi enzymes are concentrated in the perforated zones of cisternal rims both in vivo and in a cell-free system. This lateral segregation of Golgi enzymes is detectable in some stacks during steady-state transport, but it was significantly prominent after blocking endoplasmic reticulum-to-Golgi transport. Delivery of transport carriers to the Golgi after the release of a transport block leads to a diminution in Golgi enzyme concentrations in perforated zones of cisternae. The exclusion of Golgi enzymes from COPI vesicles and their transport-dependent accumulation in perforated zones argues against the current vesicle-mediated version of the cisternal maturation/progression model.     

The characteristics of protein p53 expression in the mucosal epithelium of the large intestine affected by polyps and cancer

The direct dependence between p53 expression in epithelial cells and the level of morphological malignant neoplasm was established as the result of investigation of expression of this biomolecular marker in 12 polyps and 35 colorectal cancer. It was shown that family cancer syndrome 1 type was observed in pedigrees of majority patients with p53 positive cancers.     

Retrospective monitoring of radioactive pollution in zones of the nuclear industry impact

An approach to the acquisition of retrospective information on the radioactive pollution of the territories to organize the radioecological monitoring of environment was proposed. The approach is based on the application of the method of dendrochronoindication, allowing one to obtain the retrospective information on the delivery and accumulation of radioactive and other chemicals in the growth rings of the trees. Statistical processing and the analysis of the arrays of the multidimensional retrospective data was carried out using the principal components method. It was shown that the approach proposed allows one to reveal the emergency emissions that took place in the past at the enterprises of nuclear industry and make a well-grounded selection of the monitoring sites to establish the radioecological monitoring in the zones of nuclear industry impact.     

Glutamine synthetase in the phloem plays a major role in controlling proline production

To inhibit expression specifically in the phloem, a 274-bp fragment of a cDNA (Gln1-5) encoding cytosolic glutamine synthetase (GS1) from tobacco was placed in the antisense orientation downstream of the cytosolic Cu/Zn superoxide dismutase promoter of Nicotiana plumbaginifolia. After Agrobacterium-mediated transformation, two transgenic N. tabacum lines exhibiting reduced levels of GS1 mRNA and GS activity in midribs, stems, and roots were obtained. Immunogold labeling experiments allowed us to verify that the GS protein content was markedly decreased in the phloem companion cells of transformed plants. Moreover, a general decrease in proline content in the transgenic plants in comparison with wild-type tobacco was observed when plants were forced to assimilate large amounts of ammonium. In contrast, no major changes in the concentration of amino acids used for nitrogen transport were apparent. A (15)NH(4)(+)-labeling kinetic over a 48-hr period confirmed that in leaves of transgenic plants, the decrease in proline production was directly related to glutamine availability. After 2 weeks of salt treatment, the transgenic plants had a pronounced stress phenotype, consisting of wilting and bleaching in the older leaves. We conclude that GS in the phloem plays a major role in regulating proline production consistent with the function of proline as a nitrogen source and as a key metabolite synthesized in response to water stress.     

Pheomelanin as a Binding Site for Drugs and Chemicals

Certain drugs and chemicals, such as chloroquine, chlorpromazine, and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), are bound to melanin and retained in pigment cells for long periods. This specific retention in pigmented tissues can cause adverse effects in the skin, eye, inner ear, and pigmented nerve cells of the substantia nigra of the brain. To date, all studies have been focused on eu- and neuromelanin. In the present study, we show that chloroquine, chlorpromazine, chlomipramine, paraquat, acridine orange, and nickel, which are bound to eumelanin, also bind to synthetic pheomelanin, but the binding to pheomelanin is lower. The binding varied with the cysteine content and pH, and the results indicate that the binding is complex and includes ionic interactions. In addition, we have shown that these substances also bind to synthetic thiourea-containing melanin, but to quite a low extent. We also present a microautoradiographic study on the binding of ¹⁴C-chloroquine to natural pheomelanin in vivo in yellow mice C57BL (A^y/a). Black (C57/BL) and albino (NMRI) mice were used as controls. The autoradiography demonstrated a pronounced uptake of chloroquine in the hair follicles and the dermal melanocytes in the ear of yellow mice, which was comparable to the corresponding accumulation of label in black mice. In the albino mouse, the uptake was lower and more homogeneously distributed in the skin. These results suggest that the toxicologi-cal risks of melanin-related adverse effects are applicable to persons with a high content of pheomelanin in the skin and hair.     

SV40 large T antigen is modified with O-linked N-acetylglucosamine but not with other forms of glycosylation

SV40 large T antigen has been reported to be modified with several different sugars including N-acetylglucosamine, galactose, and mannose. In this report we have reexamined the glycosylation of T antigen and found that while we could detect modification with N-acetylglucosamine, we could not detect any other sugars on the protein. Surprisingly, even though [3H]galactose could be metabolically incorporated into the protein, analysis showed that all of the radioactivity in T antigen had been converted to other species. The N-acetylglucosamine was demonstrated to be linked to the protein in the form of O-linked N- acetylglucosamine, the best characterized form of nuclear and cytoplasmic glycosylation in mammalian systems. We have localized the major site of glycosylation to the amino terminal portion of the molecule. Analysis of mutated T antigen where serines 111/112 were substituted with alanine suggest that these residues constitute a glycosylation site on the protein. These two serines fall within a typical O-linked N-acetylglucosamine glycosylation site (PSS) and are also known to be phosphorylated. Thus, it is likely that competition between phosphorylation and glycosylation occurs at this site.      

Biosynthesis of immunoglobin G in a cell-free system

Optimal conditions are selected to study biosynthesis of proteins by the microsomal cell-free system. It is established that incorporation of the radioactive precursor into anew synthesized proteins by microsomes decreases in a series: the liver, spleen, lymph nodes, bone marrow. It is shown that under malignant growth considerably higher amount of protein with the antigenic properties of immunoglobulin C is synthesized in the spleen of leukemic rats than in other organs of control leukemic animals.