Specific features of the VCSEL spectra under microwave current modulation.

The optical spectrum of a vertical-cavity surface-emitting laser under microwave frequency current modulation is asymmetric in most cases, i.e., sidebands equidistant from the carrier have unequal powers. Spectra asymmetry is conventionally explained as a result of amplitude modulation affecting a phase-modulated field, but this approach does not give a comprehensive description of the asymmetry. We performed a sequential analysis based on Maxwell's equations accounting for the nonlinear interaction of five spectral components of the laser field. This approach predicted a non-global asymmetry of the spectrum and a new resonant feature in the dependence of the second sidebands' power ratio on the injection current, which we demonstrate experimentally.

Effect of the buffer gases on the light shift suppression possibility.

We theoretically and experimentally demonstrate that the light shift of the coherent population trapping resonance frequency depends on the buffer gases pressure. The light shift suppression becomes impossible when a certain value of the buffer gases pressure is exceeded. We estimate the minimal dimensions of an atomic cell at which the zero light shift and the lowest ground-state relaxation rate can be achieved simultaneously. A new technique of the light shift cancellation by means of a feedback utilizing the RF power modulation is proposed.

Bovine satellite DNA induces heterochromatinization of host chromosomal DNA in cells of trassatellite mouse embryonal carcinoma.

Embryonal teratocarcinoma F9 cells were transfected with a fragment (3.8 kb) of bovine satellite DNA IV (Sat), which is not homologous to mouse satellite DNA. FISH analysis revealed various chromosomal integration sites of integrated Sat in different transsatellite clones. After several passages, transsatellite had a tendency to spread along chromosome bearing Sat in one of the studied lines. The integrated transsatellites were enriched with prolonged single-strand DNA regions (SSR) revealed by FISH without previous chromosomal denaturation, and were unmethylated. The observed SSR are presumably supposed to represent intermediates of transsatellite DNA instability via unequal sister chromatid exchanges. DAPI staining demonstrated that the integrated Sat induced the formation of prominent ectopic neoheterochromatin blocks in regions adjacent to integrated Sat. These blocks were located exclusively between integrated Sat and centromeric heterochromatin. Thus, mouse repetitive centromeric DNA (AT-rich, DAPI-positive) "spreads" along the chromosome in response to integration of the bovine satellite GC-rich DNA. The results obtained are discussed in the context of possible position effect variegation mechanisms operating in undifferentiated cells.

Subkilohertz enhanced-power diode-laser spectrometer in the visible.

We report on a high-performance diode-laser spectrometer operating near 657 nm with narrow linewidth (<0.6 kHz) , enhanced power (as much as 40 mW), and low drift (<10 Hz/s) . The spectrometer comprised an extended-cavity diode-laser frequency stabilized to a high-finesse optical resonator and a broad-area antireflection coated laser diode as an amplifier with a single-lobe emission pattern of good spatial purity. The spectrometer was used to record time-domain optical Ramsey spectra of laser-cooled Ca atoms with a resolution of 0.6 kHz.

Copper depletion/repletion of human ceruloplasmin is followed by the changes in its spectral features and functional properties.

Copper ions of different types were gradually eliminated from ceruloplasmin (CP1; ferro-O2-oxidoreductase, EC 1.16.3.1.) by dialyzing the enzyme against KCN. Protein was sampled 2, 4, 6, 22, and 28 h after the dialysis started. Atomic absorption allowed us to estimate the amount of copper atoms per CP molecule. Light absorption in the UV and visible regions along with fluorescence and EPR spectra were also registered. Oxidase and dismutase activities of the enzyme were measured at each step. The combination of the data thus obtained allowed us to trace the sequence of CP depletion of certain copper ions. The same methods were applied in reconstitution studies to detect the return of different types of Cu2+. The experiments were performed on CP samples differing in the amount of copper still bound after CN- treatment. It is shown that the oxidase activity is efficiently brought back to CP if, after the dialysis against cyanide, the catalytic center had preserved its type 3 Cu2+. Dismutase activity of CP did not depend greatly on the presence or absence of type 1 and type 2 copper ions. The results obtained allow a more precise evaluation of the role of different types Cu2+ in the assembly of the complex catalytic center of CP and in the accomplishment by the enzyme of its multiple functions.

Fibronectin, Cryoglobulinemia and Immune Complexes in Sjogren's Syndrome Patients.

The problem of proper diagnosis, patient's status and disease progression is very actual for autoimmune diseases. Still the diagnosis of Sjogren's syndrome is more state of art than of science. Our preliminary investigations showed that serum fibronectin of elevated molecular weight may be probably considered as one of the diagnostic criteria in Sjogren's syndrome patients. The increase of molecular weight of FN chains from 220 kDa to 250 kDa derives from relative and absolute elevation in a content of N-acetylglucosamine in FN carbohydrate chains. The present results concern the presence of FN in cryoprecipitates and circulating immune complexes in Sjogren's syndrome patients and as it has been demonstrated this parameter may be used as a prognostic sign.

Evidence for the molten globule state of human apo-ceruloplasmin.

The conformational features of copper-free ceruloplasmin (CP), as compared to the holo-protein, were evaluated utilizing far- and near-UV circular dichroism and fluorescence spectroscopy. The results obtained indicate that apo-CP maintains the secondary structure of the holo-protein, while the tertiary interactions are much weaker. In addition, the removal of copper from the holo-protein leads to the exposure of hydrophobic patches to solvent, as shown by the fact that apo-CP, at variance from the holo-protein, binds the hydrophobic probe ANS. It is proposed that the CP molecule, upon copper removal, acquires the conformational features typical of a molten globule, which might be the conformational state of CP during its biosynthesis before metal incorporation.

Embryotoxicity of silver ions is diminished by ceruloplasmin--further evidence for its role in the transport of copper.

The effect of alimentary administration of silver salts upon embryogenesis in rats was studied. Feeding of female rats throughout the term on a regular diet supplemented with AgCl did not cause alterations of their physiological functions, despite the fact that enzymatically active copper-containing ceruloplasmin (CP) was eliminated from the blood plasma. However, developmental abnormalities of embryos, their prenatal death or the 100% mortality of the newborns in the first 24 h of life was seen. Copper content in placenta and fetal tissues was strongly diminished. Cu, Zn-superoxide dismutase (SOD) activity decreased in cytoplasm of embryonic cells along with a drop, though less pronounced, in the tissues of the pregnant females. Embryotoxicity of AgCl was seriously diminished by repetitive injections of native CP to the pregnant rats. Such treatment resulted in an increase of SOD activity in placenta and embryonic tissues. The mortality of the newborns also became less. It is suggested that the embryotoxic effect of AgCl is caused by its ability to interfere with copper metabolism, in particular by altering the copper-transporting function of CP.

Serum viscosity is a sensitive test for monitoring primary Sjögren syndrome.

Primary Sjögren's syndrome (pSS) is characterized by chronic inflammation, resulting in secondary changes in serum protein content. In an attempt to evaluate disease activity we have measured serum viscosity (SV) in 41 patients with pSS and compared SV with laboratory findings such as: total proteins, gamma-globulin concentrations, titre of rheumatoid factor (RF) and level of circulating immune complexes. SV was found to correlate with these laboratory parameters. The pSS patients with low serum viscosity had worse clinical abnormalities than those with the high SV. Thus SV affords a useful monitoring test for pSS patients.