The effect of sodium selenite on cell proliferation and transformation of primary rat tracheal epithelial cells

The effects of sodium selenite (Na2SeO3) on cell proliferation and the development of preneoplastic transformed variants were studied in primary cultures of rat tracheal epithelial cells. Results revealed a biphasic effect of Na2SeO3 on cell proliferation: at concentrations between 6 x 10(-8) and 6 x 10(-6) M, it stimulated and at concentrations of approximately 2 x 10(-5) and above it inhibited cell proliferation (presumably due to toxicity). Nontoxic concentrations of Na2SeO3 (6 x 10(-8) -6 x 10(-7) M) significantly reduced the spontaneous transformation frequency. Transformation induced by the tobacco-specific nitrosamine 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was effectively inhibited by nontoxic as well as toxic concentrations of Na2SeO3. Treatment of cultures with Na2SeO3 after cessation of NNK exposure, i.e. during the selection period, also significantly reduced the transformation frequency. These experiments show that the inhibition of transformation by Na2SeO3 is not the result of an antiproliferative effect. They further indicate that the inhibitory effect occurs even when the chemical treatment occurs during the 'postinitiation' phase. Thus the inhibition of transformation by Na2SeO3 cannot solely be explained by its effects on drug metabolism.

[The preparation and identification of anti-idiotypic antibody against Plasmodium vivax at erythrocytic stages]

Through hypotonic dialyzing and gel filtration on Sephadex G200, 6H7G11 McAb-IgM (Mouse IgM) was successfully purified. Anti-6H7G11Id (Ab2) was induced in rabbit. This Ab2 was identified by agar diffusion, ELISA and competitive assays. The results showed that the Ab2 was able to combine respective Ab1 (6H7G11McAb), and the binding between Ab2 and Ab1 could be inhibited by Plasmodium vivax (P.v) antigen. Meantime, by using Ab2 thus prepared to immunize BALB/c mice, the anti-6H7G11Id (Ab3 or Ab1') was obtained with specificity of Ab1. It was revealed that the Ab2 thus prepared could mimic the antigenic determinant of P.v, and it belongs to the cross-reacted idiotype.

Cellular uptake and subcellular distribution of phosphorothioate oligonucleotides into cultured cells

A phosphorothioate oligonucleotide that has been employed to inhibit HIV-1 viral expression in chronically infected H9 cells was examined for cellular uptake and subcellular distribution. The relationship between extracellular oligonucleotide concentration and the distribution and accumulation into subcellular organelles is important to the design, potential side effects, and understanding of a therapeutically useful antisense oligonucleotide. These studies employed uptake of both 35S- and fluorescence-labeled phosphorothioate oligonucleotides. Experiments with V79, HeLa, H9, and fresh human peripheral blood monocytes indicate that accumulations of oligonucleotide inside cells exceeds the concentration of oligonucleotide in culture media by over 100 times following 1 h of exposure at 37 degrees C. Uptake is more efficient at low concentrations, suggesting a saturable process. The total oligonucleotide that remains in cells begins to reach a plateau after 45-60 min, indicating either that efflux pathways exist or that uptake is saturable. Subcellular fractionation studies with 35S-labeled phosphorothioate demonstrate the oligonucleotide is sequestered into both the nuclei and the mitochondria of cultured HeLa cells in a time-dependent manner. The subcellular fractionation was examined with fluorescence-labeled phosphorothioate by both confocal and fluorescence microscopy, which confirmed the rate and localization of oligonucleotide into cultured cells. Finally, cellular uptake is not uniform for all cells in a nonsynchronous culture.

Evaluation of a lens opacities classification system II (LOCS II) in the survey population-based sample

In the field work of population-based research, 3 groups of eyes were graded by 2 observers in LOCS II. The reproducibility of LOCS II was evaluated by agreements (85%-100%) and k values (0.661-1) obtained in our study. The satisfying results show that LOCS II is not only easy to be learned and to be applied consistently by different observers, but also good reproducibility in the field work. The longitudinal cataract study is going to be performed in our plan.

Polyneuropathy syndromes associated with serum antibodies to sulfatide and myelin-associated glycoprotein

We studied a series of 64 patients with sensory +/- motor peripheral neuropathies by comparing clinical and physiologic features to serum antibody reactivity against compounds containing sulfated carbohydrate moieties. We determined antibody reactivity by an enzyme-linked immunosorbent assay (ELISA) using purified glycolipids and glycoproteins as antigens, and we used high-performance thin-layer chromatography and Western blotting to test the specificity of results. Twelve patients with high titers of IgM antibodies directed against the myelin-associated glycoprotein (MAG) had sensory-motor polyneuropathies with physiologic evidence of demyelination. IgM antibody reactivity to MAG was associated with an IgM serum M protein in five patients. Eight other patients, most with sensory greater than motor polyneuropathies, had high titers of antibody reactivity to sulfatide but not of IgM to MAG. Two had an associated IgM paraprotein. None of the patients with selective serum antisulfatide activity had predominantly demyelinating features on physiologic testing. We conclude that (1) high ELISA titers of antibodies to MAG may be more common than previously suspected in patients with chronic demyelinating sensory-motor neuropathies, and (2) the presence of high titers of antisulfatide antibodies in serum may provide clues to the pathogenesis of otherwise idiopathic, axonal, predominantly sensory neuropathies.

[The role of beta-endorphin and pain perception in silent myocardial ischemia]

Plasma beta-endorphin (beta-END) levels were measured before, after exercise tests and at the onset of spontaneous angina in 23 anginal patients (group 1), 23 patients with silent myocardial ischemia (group 2) and 15 healthy volunteers (group 3). The pain perception in three groups was also measured. Before and after exercise, the concentration of beta-END in group 1 was significantly lower than that in group 2 and group 3. The concentration of beta-END during onset of spontaneous angina was also lower than that of angina-free period in group 1. There was no significant difference of beta-END between group 2 and 3. The values of the pain threshold and tolerance in group 1 were lower than those of group 2 and 3. These data suggested that plasma levels of beta-END may be related to occurrence of angina. The anginal patients had a hypersensitivity and hypotolerance for pain. A positive correlation was found between plasma beta-END and pain threshold, the levels of beta-END might affect the pain perception during the onset of myocardial ischemia.

Conformation of apolipoprotein B-100 in the low density lipoproteins of tangier disease. Identification of localized conformational response to triglyceride content

The low density lipoproteins (LDL) from patients with Tangier disease are enriched in triglycerides, 27% of LDL mass versus 7% for normal LDL. To study whether this unique LDL core lipid composition affects the surface disposition of apolipoprotein (apo) B-100, we analyzed the LDL by protease digestion and in competitive radioimmunoassays. Limited proteolytic digestion of Tangier LDL by Staphylococcus aureus V8 protease generated a prominent fragment of 120 kDa (cleavage site at residue 1076), which was not visible in similarly digested normal LDL. In competitive radioimmunoassay, Tangier LDL bound weakly to the apoB-specific monoclonal antibody MB20, compared with control LDL. We localized the MB20 epitope between residues 1031 and 1084 of apoB-100, probably very near residue 1076. DNA sequencing of exon 21 of apoB genomic clones (coding for residues 1014-1084) from a Tangier patient revealed no difference from the normal DNA sequence, thus eliminating a protein polymorphism as a basis for the altered protease sensitivity and antibody binding. When the triglyceride contents of Tangier LDL were reduced to 10% of mass by incubation with normal high density lipoproteins, production of the 120-kDa fragment by proteolysis decreased and MB20 binding increased in affinity, implying a change toward normal conformation of apoB-100. Thus, using two independent techniques, proteolytic digestion and binding of monoclonal antibodies, we have demonstrated an alternative conformation of apoB-100 in the vicinity of residue 1076, which reflects the content of triglycerides in the LDL particle.

Singlet-singlet energy transfer along the helix of a double-stranded nucleic acid at room temperature

An irreversible electronic energy trap has been formed in calf thymus DNA by methylating about 75% of its G bases at position N-7. This has allowed us to measure for the first time the efficiency of transfer of energy along the helix of a double-stranded nucleic acid at room temperature. It is found that about one out of every three photons absorbed by the other bases is trapped. We have also simulated the data with a stochastic model that uses the dipole-dipole interaction to calculate the efficiency of transfer. In order to approximate the experimental results, the model requires that: (i) the fluorescence quantum yield of T, C, and G in DNA be about 2 x 10(-3), which is about two orders of magnitude larger than the value of the fluorescence quantum yield reported for DNA; and (ii) the fluorescence quantum yield of A in DNA be negligibly small. Requirement (i) is consistent with energy transfer taking place before a very efficient fluorescence quenching process sets in, which could be formation of excited-state complexes (excimers) that do not fluoresce appreciably. Requirement (ii) implies a very short fluorescence lifetime for A, which is consistent with the reported absence of a significant number of photoproducts formed by A in DNA. The simulations find that, on the average, the excitation energy takes about 1.2 steps to reach the trap; that is to say, bases that are nearest and next nearest neighbors of the trap are, in effect, the only energy donors. Both intra- as well as interstrand energy transfer (the latter only for the C-trap base pair) make significant contributions. The value of the efficiency for pairwise base-base intrastrand transfer is about 60%, whereas those for base-trap intra- and interstand transfer are 90% and 80%, respectively. The corresponding values for the rate constant of transfer are 2 x 10(11), 1 x 10(12), and 4 x 10(11) s-1. Transfer is inefficient when A is the donor or the acceptor. In addition to the dipole-dipole term, the only other significant term in the expansion of the interaction potential is the dipole-quadrupole term which, however, makes only a small contribution to the overall transfer efficiency. The electron exchange interaction appears to be much less efficient than the coulombic interaction.