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At least 577 records · Page 32Linked to original sources
PubMed2000

[The retinal nerve fiber layer in glaucoma. II. The status of the nerve fiber layer and development of changes in the visual field. Prospective study].

PURPOSE: To determine whether retinal nerve fiber layer (RNFL) photographs can predict future glaucoma visual field damage. METHODS: In a prospective study 158 red free photographs of the RNFL were made from November 1994 to June 1995. 28 eyes of 19 patients with ocular hypertension (repeated intraocular pressure over 21 mmHg and normal visual fields--Peristat 433 Rodenstock--at first examination) could be re-examined for an average time of 42.3 (SD 4.5) months. RESULTS: Only in one eye with normal RNFL at the first examination typical glaucoma visual field defects appeared (6%), but in 6 of 12 eyes (50%) with photographically demonstrable RNFL defects. The difference was statistically significant. CONCLUSION: There is only a minor probability, that visual field defects would appear during 3-5 years in eyes with normal RNFL photographs (6%), but about 50% of eyes with originally found RNFL defects.

Adult↗
PubMed1986

Morphogenesis of the long tail fibers of bacteriophage T2 involves proteolytic processing of the polypeptide (gene product 37) constituting the distal part of the fiber.

Gene 37 of phage T2 codes for a protein that, as a dimer, constitutes the most distal, receptor-recognizing part of its long tail fibers. It was found that, from a plasmid carrying a fragment of gene 37 that lacked a region of the gene encoding 87 CO2H-terminal amino acid residues, a protein was expressed that was slightly larger than that present in the phage. This size difference could not be accounted for. The missing region of gene 37 and also gene 38 (which codes for the auxiliary protein required for dimerization of protein 37) were cloned. Plasmids were constructed with gene 37, or gene 37 together with gene 38, under inducible control. Independent of the presence of the latter gene, a protein was produced that had the same size as protein 37 in the phage. A pulse-chase experiment revealed that a precursor of protein 37 is synthesized and processed such that approximately 120 amino acid residues, most likely CO2H-terminal, are removed. Therefore, the protein produced from the truncated gene was larger because it cannot be processed. This fact also solved an old puzzle: an amber fragment of protein 37 of phage T2 had been found to be larger than the mature protein. The amber codon could be located 24 codons away from the normal stop codon. Obviously, the fragment cannot be processed. The existence of this fragment demonstrates that processing occurs during phage maturation.

Autoradiography↗
PubMed1972

Electromechanical coupling in tubular muscle fibers. I. The organization of tubular muscle fibers in the scorpion Leiurus quinquestriatus.

The tubular fibers of the claw-closer muscle of the scorpion have a central core containing nuclei and mitochondria. The myofibrils have the shape of thin lamellae (1 micro) extending radially from the core to the surface membrane (20 micro). The thick myofilaments are organized in a hexagonal array with orbits of 10-13 thin myofilaments. The ratio of thick-to-thin filaments is 1:5. Transverse tubular system (TS) openings are located between lamellated myofibrils. In each sarcomere two TS's are found, one on each side of the H band. The TS is composed of a transverse tubule and tubular pockets (TP). The TP's form diadic contact with the terminal cisternae of the sarcoplasmic reticulum. The TS can be traced from the cell membrane down to the cell core. The surface area of the TS was calculated to be six times that of the outer surface membrane.

Action Potentials↗
PubMedDate not supplied

Development of ultrafine polyester fiber vascular grafts with high endothelialization capability. Angiogenesis by ultrafine polyester fibers.

The authors previously showed that a vascular prosthesis made of ultrafine polyester fibers (UFPF) had high healing ability even when of low porosity. In this study, new highly porous vascular grafts fabricated from UFPF (water porosity: 3,600 ml/min/cm2, 8 mm in inner diameter and 5 cm in length), were developed and implanted in the thoracic descending aorta of dogs to evaluate their endothelialization capability. Two weeks after implantation, many colonies of endothelial cells with openings of capillary blood vessels were noted, even in the middle portion of the grafts. Numerous fibroblasts and capillary blood vessels were also observed in the synthetic walls. These results suggest that UFPF vascular grafts provide a suitable microenvironment for infiltration and proliferation of fibroblasts, which are accompanied by the capillary formation as nutrient supply; these capillaries provide multiple sources of endothelial coverage on the luminal surface. It is expected that the new, highly porous vascular grafts may have rich endothelialization capability and stable healing properties in humans.

Animals↗
PubMed2001

Historical cohort study of US man-made vitreous fiber production workers: III. Analysis of exposure-weighted measures of respirable fibers and formaldehyde in the nested case-control study of respiratory system cancer.

The most recent findings of our nested case-control study of respiratory system cancer (RSC) among male fiberglass workers showed some evidence of elevated RSC risk associated with non-baseline levels of average intensity of exposure (AIE) to respirable fibers (RFib). When adjusted for smoking, this was not statistically significant, and no trend was apparent with increasing levels of exposure. Similar findings for RSC were noted for both cumulative exposure (Cum) and AIE to formaldehyde (FOR). In this reanalysis of our nested case-control study, we explored a possible exposure-response relationship between RSC and exposure to RFib or FOR using exposure weighting as an alternative characterization of exposure. Because of the uncertainties in selecting an appropriate exposure-weighting scheme, a range of plausible time lags and unlagged/lagged time windows was considered. As in the initial analysis of the nested case-control study, RFib and FOR exposures were categorized at the deciles of the RSC case distribution. For none of the exposure weighting schemes considered did we observe an increasing RSC risk with increasing levels of RFib_Cum or RFib_AIE. The exposure-weighted estimated risk ratios (RR) for both RFib_Cum and RFib_AIE were generally lower than those obtained from an unweighted model. For FOR_Cum, RRs were generally lower for the time-lagged and unlagged time window models than for the unweighted models, although some decile-specific RRs were higher for the lagged time window models. The exposure-weighted RRs for FOR_AIE were generally lower than the unweighted RRs for all of the weighting schemes considered. This reanalysis in terms of categorized exposures reveals no exposure-response relationships that were undetected in the original analysis where unweighted exposure measures were used. In the schemes considered, exposure weighting generally reduced the estimated risk of RSC.

Adult↗
PubMed2002

Structure of fibrin gels studied by elastic light scattering techniques: dependence of fractal dimension, gel crossover length, fiber diameter, and fiber density on monomer concentration.

The concentration dependence of the structure of fibrin gels, formed following fibrinogen activation by thrombin at a constant molar ratio, was investigated by means of elastic light scattering techniques. The scattered intensity distributions were measured in absolute units over a wave-vector range q of about three decades ( approximately 3x10(2)-3x10(5) cm(-1)). A set of gel-characterizing parameters were recovered by accurately fitting the data with a single function recently developed by us [F. Ferri et al., Phys. Rev. E 63, 031401 (2001)], based on a simple structural model. Accordingly, the gels can be described as random networks of fibers of average diameter d and density rho, entangled together to form densely packed and spatially correlated blobs of mass fractal dimension D(m) and average size (or crossover length) xi. As previously done for d, we show here that the recovered xi is also a good approximation of a weight average, namely, d approximately sqrt[ (w)] and xi approximately (w). By varying the fibrinogen concentration c(F) between 0.034-0.81 mg/ml, gels with 100> or =xi> or =10 microm, 100< or =d< or =200 nm, 1.2< or =D(m)< or =1.4, and constant rho approximately 0.4 mg/ml were obtained. The power-law c(F) dependencies that we found for both xi and d are consistent with the model, provided that the blobs are allowed to partially overlap by a factor eta likewise scaling with c(F) (2> or =eta> or =1). Recasting the whole dataset on a single master curve provided further evidence of the similarity between the structures of all the gels, and confirmed the self-consistency of the model.

Fibrin↗
PubMed2001

Fiber mode conversion with tilted gratings in an optical fiber.

The mode coupling in double-sided tilted gratings between the LP01 and LP11 modes is analyzed for three different excitation conditions. It is found that a number of modes, including various LP11q modes with different polarization states and TE01, TM01, and HE21 modes, can be formed through the mode conversion process in the gratings and with a linear combination of four different LP11 modes. Efficient single-sided and double-sided tilted gratings are demonstrated. The tilted gratings presented exhibit LP01-to-LP11 mode coupling over a spectral width as wide as 160 nm. The transmission spectra of the tilted fiber gratings agree well with the spectrum predicted by the coupled-mode analysis.

Journal Article↗
PubMed2006

High-speed fiber-optic spectrometer for signal demodulation of inteferometric fiber-optic sensors.

We demonstrated a spectrometer that is capable of acquiring the spectra from interferometric fiber-optic sensors at high speed. The high spectrum acquisition rate is enabled by transforming the spectral information from frequency domain to time domain using a dispersive element and high-speed data acquisition devices. Preliminary results show that the prototype system can record 10,000 frames of spectra per second and achieve a spectrum measurement resolution of 15 nm. Better performance could be realized by using a Raman amplifier and by optimizing the parameters of the system and data processing methods.

Journal Article↗
PubMed2006

Low optical insertion-loss and vacuum-pressure all-fiber acetylene cell based on hollow-core photonic crystal fiber.

We report a novel and easy-to-implement hollow-core photonic crystal fiber cell fabrication technique based on helium diffusion through silica. The formed gas cells combine low optical insertion loss (1.8 dB) and vacuum acetylene pressure (microbar regime). The estimates of the final gas pressure, using both Voigt interpolation and electromagnetically induced transparency, show a good match with the initial fitting pressure.

Journal Article↗
PubMed2007

Fiber-optic pH-sensors in long-period fiber gratings using electrostatic self-assembly.

A novel pH sensor based on the deposition of electrostatic self-assembled polyallylamine hydrochloride and polyacrylic acid on the cladding of a long-period fiber grating has been designed. The overlay thickness is of the order of magnitude of the light wavelength used to interrogate the sensor. A theoretical model of multilayer cylindrical waveguides based on coupled-mode theory has been used to predict the position of the attenuation bands as a function of the overlay thickness. A study of the role that pH plays in the thickness of the sensitive overlay was carried out. Experimentally, a wavelength shift of the attenuation bands of up to 85 nm was obtained in the 4-7 range of pH units. The results are reproducible, which indicates the possibilities of a multiple-use sensor.

Journal Article↗
PubMedDate not supplied

Small intestinal stromal tumors with skeinoid fibers in neurofibromatosis: report of four cases with ultrastructural study of skeinoid fibers from paraffin blocks.

Small intestinal stromal tumors (SIST) with skeinoid fibers (SF) are reported in four patients with neurofibromatosis. SF appeared as intercellular eosinophilic globules that stained positively on periodic acid-Schiff stain and bluish on Masson trichrome stain, like those reported previously. Electron microscopic confirmation of SF was carried out on tissue retrieved from paraffin blocks, which revealed diagnostic ultrastructural features of SF. The association of SIST with SF and neurofibromatosis enhances the diagnostic value of SF as a marker of neurogenic spindle cell tumors. This study also underscores the importance of electron microscopy for differentiation of SF from pseudoskeinoid structures, which may mimic SF on light microscopic examination.

Adult↗
PubMed1975

[Neonatal hypotonias with congenital disproportion of various types of muscular fiber, especially type I fibers. Demonstration of the familial character of this new entity].

Two sisters presenting with benign congenital hypotonia are reported. In both cases the muscle biopsies demonstrated the same pathological pattern, consisting in an abnormal size disproportion between the two main cytoenzymological types of muscle fibers. Their father, exhibiting a slight and diffuse muscle weakness, showed a closely related histological aspect. These three cases bring the first evidence of a familial transmission of this new entity. Its relationship with the other types of "congenital myopathies" is discussed.

Adult↗
PubMed1989

[Fiber emissions from weathered asbestos cement products. 1. Fiber release in ambient air].

Emissions of fibrous aerosols were measured on buildings with weathered and corroded asbestos-cement-plates (roofing and facade shingles) by means of an already published equipment and procedure. The measured emission factors for asbestos fibers longer than 5 microns were in the range of 10(6) to 10(8) fibers/m2.h. They depended on the type of the AC-plates as well as on their age and corrosion intensity.

Air Pollutants↗
PubMed1983

[Determination of average fiber density (single fiber lead), quantitative electromyography and serum CK in the detection of Duchenne carriers].

The fibre density of the extensor digitorum communis muscle was examined with a monopolar single fiber electrode in 2 definite, one probable and 15 possible Duchenne-carriers. In addition serum-CK was evaluated three times in intervals of a least one week. The fibre density was increased in one definite, one probable and 4 possible carriers (greater than 1.6). The highest value was 2.0. Excepting one case the increase of fibre density was accompanied by an increase of serum-CK (greater than 60 mg%). The highest value of CK was 1626 mg%. The conventional EMG was pathological in 2 cases. In no case with an increase of CK or with pathological EMG the fibre density was normal. The fibre density is an unspecific but rather sensible indicator of Duchenne-carriers but as we could observe in a definite carrier, negative results do not exclude carriers.

Adolescent↗
PubMed1978

[Study of structural changes in muscle fiber contractile proteins using polarization ultraviolet fluorescent microscopy. IV. Several features of the conformational changes in F-actin during muscle fiber relaxation].

Using the polarized ultraviolet fluorescent microscopy in the presence of a fluorescence quencher (acrylamide, NO3-) it has been shown that actin tryptophanyls are oriented with their short axes perpendicular to the long axis of the thin filament. Fluorophores in hardly accessible sites of the macromolecule have a more pronounced anisotrophy of orientation in comparison with those in the protein sites easily available by a fluorescence quencher. During the muscle fiber relaxation, conformational changes of F-actin take place which embrace seemingly the sites of subunits, close to the surface of macromolecule, and make difficult the penetration of univalent ions and neutral molecules deep into the protein macromolecule. Some connection between conformational changes of the surface areas of F-actin subunits and the actin incapability of combining with HMM in the presence of ATP is assumed.

Acrylamides↗