DNA damage in Wistar rats exposed to dithiocarbamate pesticide mancozeb.

Pesticides are used in large amounts in agriculture and the evaluation of their toxic effects is of major concern to public and environmental health. The aim of the present study was to investigate the genotoxic potential of a commercial formulation of the fungicide mancozeb by the micronucleus test in bone marrow and the comet assay in total blood of Wistar rats. Adult male Wistar rats were treated with a solution of mancozeb at a concentration of 40 mg/kg/day, administered intraperitoneally for 18 consecutive days, and compared to a control group. The results indicate that mancozeb induced significantly higher DNA damage as detected by the comet assay and increased the frequency of micronuclei. The results show that mancozeb is genotoxic and may adversely affect the DNA integrity of exposed organisms.

Core level (S 2p) excitation and fragmentation of the dimethyl sulfide and dimethyldisulfide molecules.

Electronic excitation and ionic dissociation of dimethylsulfide (DMS) and dimethyldisulfide (DMDS) have been studied around the S 2p edge using synchrotron radiation and time-of-flight mass spectrometry techniques. Mass spectra were obtained for both molecules, below, on and above the well defined resonances observed in the S 2p photoabsorption spectrum and centered at approximately 166 eV photon energy. Ab initio IS-CASSCF calculations were performed for a better understanding of the photoabsorption spectra. Similar calculations were also performed for the H(2)S molecule, in order to establish a bench mark. For both molecules, a higher fragmentation degree is observed with increasing photon energy. In the DMDS case, selective fragmentation was observed in the formation of the [CH(n)S](+) ions at the first S 2p resonance (corresponding to excitation to a σ*SS state) and in the formation of the [S(2)](+) and [S](+) ions at the third S 2p resonance (corresponding to excitation to a σ*CS state). Previously unreported doubly charged ([S](2+), [CH(3)](2+)) are observed for DMS and DMDS.

Cryptococcosis in HIV-AIDS patients from Southern Brazil: Still a major problem.

INTRODUCTION: Cryptococcus neoformans is an opportunistic pathogen that causes ∼15% mortality in AIDS patients. Rio Grande City, Rio Grande do Sul (RS), Brazil, has the highest national rate of HIV/AIDS, considering cities with population more than 100,000 habitants. OBJECTIVE: We aimed to evaluate the clinical and epidemiological profile of cryptococcosis in a reference service for HIV-AIDS patients in the South region of Brazil, over seven years. Material and methods A retrospective study was performed including all cryptococcosis cases diagnosed at the University Hospital, Federal University of Rio Grande (UH-FURG) between January 2010 and December 2016. RESULTS: Seventy cases of cryptococcosis were diagnosis from 2010 to 2016 in the UH-FURG in the seven years of the study. These numbers were responsible for 2.1% to 8.1% of the hospitalizations/year for HIV patients. All were caused by C. neoformans infection (95% C. neoformans var. grubii VNI and 5% C. neoformans var. grubii VNII). Neurocryptococcosis was the major clinical manifestation and cryptococcosis was the HIV- defining condition in 40% of patients. The period of hospitalization was an average of 39.3 days (SD=31.3), and more than half of patients (53%; 37/70) died after a mean of 82 days. DISCUSSION: The present study showed the importance of cryptococcosis as an AIDS-defining disease in HIV-AIDS patients in a tertiary hospital from Southern Brazil. More investment is necessary to reduce the impact of this opportunistic mycosis in HIV-AIDS patients from southern Brazil.

X-ray laser microscopy of rat sperm nuclei.

The development of high brightness and short pulse width (< 200 picoseconds) x-ray lasers now offers biologists the possibility of high-resolution imaging of specimens in an aqueous environment without the blurring effects associated with natural motions and chemical erosion. As a step toward developing the capabilities of this type of x-ray microscopy, a tantalum x-ray laser at 44.83 angstrom wavelength was used together with an x-ray zone plate lens to image both unlabeled and selectively gold-labeled dried rat sperm nuclei. The observed images show approximately 500 angstrom features, illustrate the importance of x-ray microscopy in determining chemical composition, and provide information about the uniformity of sperm chromatin organization and the extent of sperm chromatin hydration.

Influence of pulse duration on ultrashort laser pulse ablation of biological tissues.

Ablation characteristics of ultrashort laser pulses were investigated for pulse durations in the range of 130 fs-10 ps. Tissue samples used in the study were dental hard tissue (dentin) and water. We observed differences in ablation crater morphology for craters generated with pulse durations in the 130 fs-1 ps and the 5 ps-10 ps range. For the water experiment, the surface ablation and subsequent propagation of stress waves were monitored using Mach-Zehnder interferometry. For 130 fs-1 ps, energy is deposited on the surface while for longer pulses the beam penetrates into the sample. Both studies indicate that a transition occurs between 1 and 5 ps.

Experimental and computational laser tissue welding using a protein patch.

An in vitro study of laser tissue welding mediated with a dye-enhanced protein patch was conducted. Fresh sections of porcine aorta were used for the experiments. Arteriotomies were treated using an indocyanine green dye-enhanced collagen patch activated by an 805-nm continuous-wave fiber-delivered diode laser. Temperature histories of the surface of the weld site were obtained using a hollow glass optical fiber-based two-color infrared thermometer. The experimental effort was complemented by simulations with the LATIS (LAser-TISsue) computer code, which uses coupled Monte Carlo, thermal transport, and mass transport models. Comparison of simulated and experimental thermal data indicated that evaporative cooling clamped the surface temperature of the weld site below 100 °C. For fluences of approximately 200 J/cm2, peak surface temperatures averaged 74°C and acute burst strengths consistently exceeded 0.14×106 dyn/cm (hoop tension). The combination of experimental and simulation results showed that the inclusion of water transport and evaporative losses in the computer code has a significant impact on the thermal distributions and hydration levels throughout the tissue volume. The solid-matrix protein patch provided a means of controllable energy delivery and yielded consistently strong welds. © 1998 Society of Photo-Optical Instrumentation Engineers.

Effects of aluminum chloride on the kinetics of rat cortex synaptosomal ATP diphosphohydrolase (EC 3.6.1.5).

Aluminum chloride (AlCl3), a neurotoxic compound, inhibited ATP diphosphohydrolase activity of synaptosomes obtained from cerebral cortex of adult rats. The metal ion significantly inhibited ATPase and ADPase activities of the enzyme at all concentrations tested in vitro (0.01, 0.05, 0.5, 5, and 10 mM) in the presence of 1.5 mM calcium. When tested in the absence of Ca2+, and with increasing amounts of Al3+, enzyme activity remained below basal levels, suggesting that the trivalent cation Al3+ is not a substitute for the divalent cation Ca2+ in ATP-Ca2+ and ADP-Ca2+ complexes. The Al3+ inhibition was competitive with respect to Ca2+. The enzyme inhibition was reversed by the addition of deferoxamine (DFO). NaF significantly inhibited ATP diphosphohydrolase activity, and this inhibition was reversed by the addition of Ca2+ to the medium. Such inhibition was not potentiated by AlF4, which is an inhibitor of cation-transport ATPases.

Silicon adsorption in defective carbon nanotubes: a first principles study.

The electronic and structural properties of an (8, 0) single-walled carbon nanotube (SWNT) with a single vacancy and interacting with a Si atom are studied using first principles calculations based on the density-functional theory. Initially, the Si atom is positioned in the site above the vacancy, with its position fixed until the nanotube geometry is fully relaxed. After that, the Si atom approaches the tube and it is shown that one C atom is displaced outwards forming a bump. The final configuration, as well as each step of the process, is studied in detail and the resulting band structures and the total charge densities are systematically analysed.

A temporal analysis of sexual activity in a natural population of Drosophila willistoni.

We have analyzed the mating activity of F1 flies in mating chamber from five samples of wild Drosophila willistoni females. The files were collected from an area (in south Brazil) that has well-defined seasons and considerable variation in temperature and in the abundance of drosophilids. We estimated copulation frequency at first five minutes of observation, copulation frequency at ninety minutes of observation and copulation latency. We did not observe differences in the total copulation frequency throughout seasons, as opposed to copulation frequency in the beginning of the observation period and to copulation latency which varied significantly. The results show that mating activity in a natural population can vary along with the seasons and that this variation can be correlated to some environmental factor. Mating activity tended to be higher during high warm temperature periods, when the flies were abundant.

Frequency doubling of ultrashort laser pulses in biological tissues.

Theoretical and experimental studies of second-harmonic generation (SHG) in biological tissues was performed by use of ultrashort laser pulses (<1 ps). A simplified one-dimensional model for the generation and the propagation of frequency-doubled light inside tissue was developed. This model was tested in vitro against measurements of pig and chicken tissue and human tooth. The experimental results indicate that the intensity of SHG varies significantly among tissue types and between test sites in individual tissue. Possibilities of using this nonlinear tissue property in imaging and diagnostics are discussed.

Measurement of spatial gain distribution for a neonlike germanium 19.6-nm laser.

We measure the transverse spatial distribution of the gain region for the 19.6-nm neonlike germanium laser line by use of a short amplifier, which is backlit by a longer laser, both of which are created by illumination of a germanium slab target with a series of short 100-ps pulses from the Nova laser. The backlighting technique enables us to reduce greatly the refraction effects that dominated previous imaging experiments and made direct gain measurements impossible. Measurements are made with a two-dimensional high-resolution spatial-imaging diagnostic, and simulations of the gain are compared with experiments.

Distribution of transposable elements in neotropical species of Drosophila.

The phylogenetic distribution of transposable families, P, gypsy, hobo, I, and mariner has been analyzed in 33 species of 11 groups of neotropical Drosophila and a Drosophilidae species Zygotrica vittimaculosa, using squash blot and dot blot. Genomic DNA of almost all neotropical species tested hybridized with gypsy probe and some species showed a particularly strong hybridization signal, as D. gaucha, D. virilis, and species of flavopilosa group. The hobo element was restricted to melanogaster group and some strains of D. willistoni. Only D. simulans DNA showed hybridization to mariner probe in all species tested and D. simulans and D. melanogaster showed hybridization with I element probe. P element homologous sequence was present in D. melanogaster and all species and strains of the willistoni and saltans groups tested. The presence of at least one P-homologous sequence was detected in Drosophila mediopunctata. This one was the only P-bearing species of all six tested from the tripunctata group. Four different pairs of primers homologous to segments of the canonical sequence of D. melanogaster's P were used to amplify specific sequences from D. mediopunctata DNA, showing the occurrence of seemingly well-conserved P-homologous sequences.

Birefringence characterization of biological tissue by use of optical coherence tomography.

An improved polarization-sensitive optical coherence tomography (OCT) system is developed and used to measure birefringence in porcine myocardium tissue and produce two-dimensional birefringence mapping of the tissue. Signal-to-noise issues that cause systematic measurement errors are analyzed to determine the regime in which such measurements are accurate. The advantage of polarization-sensitive OCT systems over standard OCT systems in avoiding image artifacts caused by birefringence is also demonstrated.

Severe lateral luxation and root fracture: report of a case with 5-year follow-up.

A case of severe lateral luxation and root fracture in upper incisors is reported. Treatment involved the repositioning and fixation of the injured teeth and endodontic treatment with calcium hydroxide. The importance of long-term follow-up is emphasized.

Evaluation of optical coherence quantitation of analytes in turbid media by use of two wavelengths.

We introduce a novel method for determining analyte concentration as a function of depth in a highly scattering media by use of a dual-wavelength optical coherence tomography system. We account for the effect of scattering on the measured attenuation by using a second wavelength that is not absorbed by the sample. We assess the applicability of this technique by measuring the concentration of water in an Intralipid phantom, using a probe wavelength of 1.53 microm and a reference wavelength of 1.31 microm. The results of our study show a strong correlation between the measured absorption and the water content of the sample. The accuracy of the technique, however, was limited by the dominance of scattering over absorption in the turbid media. Thus, although the effects of scattering were minimized, significant errors remained in the calculated absorption values. More-accurate results could be obtained with the use of more powerful superluminescent diodes and a choice of wavelengths at which absorption effects are more significant relative to scattering.

Generation of a 45-ps-duration 15.5-nm x-ray laser.

Using a series of 100-ps optical pump pulses separated by 300 ps, we have produced 45-ps FWHM output pulses in neonlike yttrium operating at a wavelength of 15.5 nm. This is to our knowledge the shortest-pulse collisionally pumped x-ray laser yet produced. The importance of using a traveling-wave pump to increase the output power is also discussed.

Collagen structure and nonlinear susceptibility: effects of heat, glycation, and enzymatic cleavage on second harmonic signal intensity.

BACKGROUND AND OBJECTIVE: Helical macromolecules such as collagen and DNA are characterized by nonlinear optical properties, including nonlinear susceptibility. Because collagen is the predominant component of most biological tissues, as well as the major source of second harmonic generation (SHG), it is reasonable to assume that changes in harmonic signal can be attributed to structural changes in collagen. The purpose of this study is to determine whether various modifications of collagen structure affect second harmonic intensity. STUDY DESIGN/MATERIALS AND METHODS: SHG was measured in tissues from cows, humans, and chickens. The effects of beam polarization, thermal denaturation, glyco-oxidative damage, and enzymatic cleavage of tissues on second harmonic intensity was studied. RESULTS: The second harmonic intensity differed considerably among different tissues, as did the effect of the incident beam polarization. In structurally modified collagen, SHG was significantly degraded from SHG in intact collagen. CONCLUSION: These structural modifications are representative of changes that occur in pathophysiologic conditions such as thermal injury, diabetes, tumor invasion, and abnormal wound healing. The ability to assess these changes rapidly and noninvasively has considerable clinical applicability. SHG analysis might provide a unique tool for monitoring these structural changes of collagen.

Dye-enhanced protein solders and patches in laser-assisted tissue welding.

OBJECTIVE: This study examines the use of dye-enhanced protein bonding agents in 805 nm diode laser-assisted tissue welding. A comparison of an albumin liquid solder and collagen solid-matrix patches used to repair arteriotomies in an in vitro porcine model is presented. SUMMARY BACKGROUND DATA: Extrinsic bonding media in the form of solders and patches have been used to enhance the practice of laser tissue welding. Preferential absorption of the laser wavelength has been achieved by the incorporation of chromophores. METHODS: Both the solder and the patch included indocyanine green dye (ICG) to absorb the 805 nm continuous-wave diode laser light used to perform the welds. Solder-mediated welds were divided into two groups (high power/short exposure and low power/long exposure), and the patches were divided into three thickness groups ranging from 0.1 to 1.3 mm. The power used to activate the patches was constant, but the exposure time was increased with patch thickness. RESULTS: Burst pressure results indicated that solder-mediated and patched welds yielded similar average burst strengths in most cases, but the patches provided a higher success rate (i.e., more often exceeded 150 mmHg) and were more consistent (i.e., smaller standard deviation) than the solder. The strongest welds were obtained using 1.0-1.3 mm thick patches, while the high power/short exposure solder group was the weakest. CONCLUSIONS: Though the solder and patches yielded similar acute weld strengths, the solid-matrix patches facilitated the welding process and provided consistently strong welds. The material properties of the extrinsic agents influenced their performance.

Imaging of hard- and soft-tissue structure in the oral cavity by optical coherence tomography.

We have developed a prototype optical coherence tomography (OCT) system for the imaging of hard and soft tissue in the oral cavity. High-resolution images of in vitro porcine periodontal tissues have been obtained with this system. The images clearly show the enamel-cementum and the gingiva-tooth interfaces, indicating OCT is a potentially useful technique for diagnosis of periodontal diseases. To our knowledge, this is the first application of OCT for imaging biologic hard tissue.

Mapping of Birefringence and Thermal Damage in Tissue by use of Polarization-Sensitive Optical Coherence Tomography.

We demonstrate cross-sectional birefringence- and polarization-independent backscatter imaging of laser-induced thermal damage in porcine myocardium in vitro, using a polarization-sensitive optical coherence tomography system. We compare the generated images with histological sections of the tissue and demonstrate that birefringence is a more sensitive indicator of thermal damage than is backscattered light. Loss of birefringence in thermally damaged regions is quantified and shown to have significant contrast with undamaged sections of the tissue. A detailed theoretical analysis of the birefringence measurements is provided, including a calculation of the systematic errors associated with background noise, system imperfections, and tissue dichroism.