Nickel plasma produced by 532-nm and 1064-nm pulsed laser ablation

A comparison between laser ablation of nickel in vacuum by using 532-and 1064-nm Nd:YAG (Yttrium Aluminium Garnet) laser wavelengths, with an intensity of 5 × 10⁹ W/cm², is reported. Nanosecond pulsed ablation produces high nonisotropic emission of neutrals and ionic species. For 532-nm laser irradiation, mass quadrupole spectrometry, coupled to electrostatic ion deflection and time-of-flight measurements, allows estimation of the energy distributions of the emitted species from plasma. For 1064-nm laser ablation, a cylindrical electrostatic ion analyzer permits one to measure the yield and the charge state of the emitted ions and reconstruct the ion energy and charge state distributions. Neutrals show typical Boltzmann-like distributions, while ions show Coulomb-Boltzmann-shifted distributions depending on their charge state. Surface profiles of the ablated craters permitted study of the ablation threshold and yields of nickel in vacuum versus the laser fluence. The plasma temperature was evaluated using experimental data. Special regard is given to the ion acceleration process occurring inside the plasma due to the high electrical field generated at nonequilibrium plasma conditions and the angular distribution of the emitted species. Published in Russian in Fizika Plazmy, 2008, Vol. 34, No. 7, pp. 598–606. The text was submitted by the authors in English.     

Evaluation of acute corneal damage induced by 222-nm and 254-nm ultraviolet light in Sprague–Dawley rats

Two hundred twenty-two nanometres ultraviolet (UV) light produced by a krypton–chlorine excimer lamp is harmful to bacterial cells but not skin. However, the effects of 222-nm UV light exposure to the eye are not fully known. We evaluated acute corneal damage induced by 222- and 254-nm UV light in albino rats. Under deep anaesthesia, 6-week-old Sprague–Dawley albino rats were exposed to UV light. The exposure levels of corneal radiation were 30, 150, and 600?mJ/cm². Epithelial defects were detected by staining with fluorescein. Superficial punctate keratitis developed in corneas exposed to more than 150?mJ/cm² of UV light, and erosion was observed in corneas exposed to 600?mJ/cm² of UV light. Haematoxylin and eosin staining also showed corneal epithelial defects in eyes exposed to 254-nm UV light. However, no damage developed in corneas exposed to 222-nm UV light. Cyclobutane pyrimidine dimer-positive cells were observed only in normal corneas and those exposed to 254-nm UV light. Although some epithelial cells were stained weakly in normal corneas, squamous epithelial cells were stained moderately, and the epithelial layer that was detached from the cornea exposed to 600?mJ/cm² of light was stained intensely in corneas exposed to 254-nm UV light. In the current study, no corneal damage was induced by 222-nm UV light, which suggested that 222-nm UV light may not harm rat eyes within the energy range and may be useful for sterilising or preventing infection in the future.     

To the 30-nm chromatin fiber and beyond

Chromatin fibers are intrinsically dynamic macromolecular complexes whose biological functions are intimately linked with their structure and interactions with chromatin-associated proteins (CAPs). Three-dimensional architectural transitions between or within the two co-existing chromatin types referred to as euchromatin and heterochromatin have been associated with activation or repression of nuclear functions. The presence of specific subsets of chromosomal proteins co-existing with the different chromatin conformations suggests a functional significance for their co-localization. The major points of emphasis of this review will assess the structure, function and recently documented exchanges amongst various members of the CAP family.     

Kinetics of the 580-nm ultrafast bacteriorhodopsin transient.

We have observed, by low-temperature picosecond spectroscopy, a photo-induced transient at 580 nm in light-adapted bacteriorhodopsin. The transient was characterized by bleaching in the 550-585-nm regions within 6 ps and recovery in approximately 20 ps. The spectral intensity of the transient is found to be enhanced at lower temperatures, and the lifetime slightly elongated.     

Stereo electron microscopy of the 25-nm chromatin fibers in isolated nuclei

The morphological effects of epidermal growth factor (EGF) on human carcinoma cells A-431 have been examined by scanning electron microscopy. These flat polygonal cells normally exhibit only small membrane folds, but show extensive ruffling and extension of filopodia within 5 min of exposure to EGF at 37 degrees C. This ruffling activity is transient, subsiding within another 5--15 min, but several other changes in surface morphology follow. Within the first hour of exposure to the hormone, the cell surface becomes exceedingly smooth and the nuclei seem to protrude above the plane of the otherwise thin monolayer, giving the cells a "fried egg" appearance. Cells at the edges of colonies gradually retract from the substrate, leading to reorganization, by 12 h, of the monolayer into multilayered colonies. EGF thus induces both rapid and long-term alterations in the morphology of these epidermoid cells.     

DNA-containing extracellular 50-nm particles in the ileal Peyer's patch of sheep

Follicles of the ileal Peyer's patch are sites of B cell proliferation and of diversification of the primary immunoglobulin repertoire in ruminants. We demonstrate here that 50-nm carbonic anhydrase-reactive particles released in the intercellular space in the follicle-associated epithelium of the ileal Peyer's patch of lambs contain DNA protected with a detergent-resistant membrane. We named these particles DiCAPs (DNA in carbonic anhydrase particles). DiCAPs can be purified from a suspension collected from ileal Peyer's patch follicles by sedimentation in a sucrose gradient. The DiCAP membrane is resistant to several ionic and non-ionic detergents alone, but can be disrupted by a combination of Triton X-100 and proteinase K. Differential nuclease treatment of purified DiCAPs indicates that they contain DNA. Digestion of DiCAP DNA with six-base pair restriction enzymes produces smears, suggesting that individual DiCAPs contain unique sequences. Nonetheless, the size of DiCAP DNA is smaller (approximately 16 kb) than that of lamb genomic DNA. Polymerase chain reaction and sequence analysis of DiCAP DNA reveals the presence of light and heavy chain variable genes as well as housekeeping genes. The data demonstrate the presence of DNA in these extracellular particles, and suggest a role of DiCAPs in transfer of DNA between cells within the ileal Peyer's patch. This raises the possibility of a novel form of communication between cells mediated by nucleic acids.     

Isolation of 10-nm filaments from astrocytes in the mouse optic nerve

Astroglial filaments approximately 10 nm in diameter were isolated from degenerated mouse optic nerves by Triton X-100 and DNase I treatments followed by sucrose density gradient centrifugation. 2-4 wk after bilateral enucleation, optic nerves contained virtually a single population of 10-nm filaments (astroglial filaments), free from neurofilaments. In negative-staining and thin-section electron microscopy, the isolated filaments were seen as nonbranching linear structures with smooth contour, and were morphologically identical to those in situ. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed the isolated filaments to be composed of two major polypeptides with molecular weights of 45,000 and 55,000, present in an approximate molar ratio of 1:1. These findings, together with the results of one-dimensional peptide mapping and solubility study, indicate that the astroglial filaments in the mouse optic nerve are primarily composed of these two polypeptides.     

Mutation induction by monochromatic 254-nm and 365-nm radiation in strains of Escherichia coli that differ in repair capability

Mutation to tryptophan independence after exposure to radiation at the monocrhomatic wavelengths of 254 and 365 nm was studied and compared in 7 strains of Escherichia coli B/r that differ in repair capability. Efficient mutation induction was obtained with both 254-nm and 365-nm radiation with strains WP2 (wild-type), WP2s (uvrA), WP6s (polA uvrA). Mutants were not induced at either wavelength in the lexA strain WP5 or the recA strains WP10 and WP100. These results support the induction of mutants with 365-nm radiation through the error-prone (SOS) pathway of postreplication repair. Log-log plots of tryptophan revertant data at 254 nm showed the expected slopes of approximately 2.0 over the entire influence range tested. In contrast, similar plots of revertant data at 365 nm were complex in all cases tested: at low fluence values (survival greater than 0.5) in all cases where reversion occurred the slopes were approximately 1.0, while at higher fluences (survival less than 0.5) the slopes of the log-log plots were approximately 3.0 with strains WP2s and WP6s, approximately 4.0 with strain WP6 and approximately 6.0 with strain WP2. Differential sensitivity of components of excision and postreplication repair systems to 365-nm radiation may account for the 2-part mutation curves obtained with uvr⁺ rec⁺ lex⁺ strains. It is proposed that efficient error-free repair of mutational lesions occurs at 365-nm fluences below 2–4×10⁵ J m²⁻; at greater 365-nm fluences, error-free excision repair may be selectively inhibited, forcing a greater fraction of mutational lesions to be processed by the error-prone component of the postreplication repair system. The similarity of the mutational responses of WP2s and WP6 at 365 nm supports the selective inhibition of error-free excision repair.     

Features of intermediary steps around the 688-nm substance in the heme oxygenase reaction

The degradation of protoheme in the heme oxygenase reaction involves three oxidation steps: from protoheme to hydroxyheme, from hydroxyheme to a 688-nm substance, a protein-bound intermediate, and from the 688-nm substance to a biliverdin-iron complex. The 688-nm substance has a ferrous iron and it readily binds carbon monoxide to form a CO-complex, called the 638-nm substance (Yoshida, T., Noguchi, M., & Kikuchi, G. (1980) J. Biochem. 88, 557-563). The ferric 688-nm substance was prepared from the 638-nm substance by the addition of potassium ferricyanide together with aspiration to eliminate CO. The ferric 688-nm substance did not show any distinct absorption maximum in the red region of the absorption spectrum. The ferric 688-nm substance was readily reduced on the addition of the NADPH-cytochrome P-450 reductase system, but the ferric 688-nm substance could also be reduced spontaneously though at a very low rate. The ferrous 688-nm substance free from excess reducing agents was prepared by passing the 638-nm substance through a column of Sephadex G-25. The ferrous 688-nm substance was degraded to a biliverdin-iron complex much more rapidly in the presence of the NADPH-cytochrome P-450 reductase system than in its absence, indicating that a reducing equivalent is essential for the initiation of heme degradation even when starting from the ferrous 688-nm substance. Cyanide was found to bind to the ferrous 688-nm substance to form a stable compound; the cyanide compound formed could revert to neither the ferrous 688-nm substance nor the 638-nm substance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prolonged lifetime of the 410-nm intermediate of bacteriorhodopsin in the presence of guanidine hydrochloride.

Prostatic binding protein (PBP) is a quantitatively important steroid-binding protein present in rat ventral prostate. Electrophoresis on SDS-containing polyacrylamide gels shows that PBP is composed of two subunits, F and S having molecular weights of 16,000 and 18,000. Upon reduction these subunits dissociate further into smaller components. Translation of mRNA from rat ventral prostate in a wheat germ cell-free system or in $\text{Xenopus}$ oocytes results in the formation of polypeptides immunoprecipitable with an anti-PBP antiserum. However, as opposed to the wheat germ system, only the oocytes synthesize polypeptides, that are electrophoretically identical to those of native cytosolic PBP.     

Antibodies against Tetrahymena 14-nm filament-forming protein recognize the replication band in Euplotes

Tetrahymena 14-nm filament-forming protein (49K protein) is a structural protein which is involved in activity of the pronuclei during conjugation (O. Numata, T. Sugai, and Y. Watanabe (1985) Nature (London) 314, 192-194). Using monoclonal and polyclonal antibodies, we here demonstrate the presence of a cross-reactive protein (CRP-49) within the macronuclear replication bands of Euplotes harpa and E. eurystomus which is recognized by anti-49K protein antibodies. Immunoblotting reveals that both monoclonal and polyclonal antibodies cross-react to a protein with an apparent molecular mass of 50 kDa in an E. harpa cell extract and to a protein of 49 kDa in a macronuclear extract of E. eurystomus. The antibodies used in this study have no effect upon in vitro DNA synthesis in the replication band of E. eurystomus.