Photorefractive keratectomy for astigmatism greater than -2.00 diopters in eyes with low, high, or extreme myopia

PURPOSE: To assess the efficacy of excimer laser photorefractive astigmatic keratectomy (PARK) in correcting astigmatism of more than -2.00 diopters (D) in eyes with low, high, and extreme myopia. SETTING: Pusan National University Hospital, Pusan, Korea. METHODS: Eighty-five patients (110 eyes) whose spherical error ranged from -3.00 to -13.00 D and cylinder ranged from -2.00 to -5.50 D had PARK with a VISX Twenty-Twenty excimer laser; follow-up was 6 months. All cases of myopic astigmatism were treated using the elliptical method and multizone ablation technique. Eyes were divided into 3 groups: low myopia, less than 6.00 D (n = 47); high myopia, from 6.25 to 10.00 D (n = 43); extreme myopia, over 10.25 D (n = 20). Alpins vector analysis was used to calculate the astigmatic change. RESULTS: By vector analysis, the success rate of astigmatic correction was more predictable in the low and high myopia groups than in the extreme myopia group (P < .05). There was little improvement in astigmatism in the extreme myopia group. CONCLUSION: Using PARK to correct astigmatism greater than -2.00 D in eyes with myopia less than -10.00 D tended to result in undercorrection; astigmatic correction in eyes with myopia over 10.25 D was minimal.     

Distinguishing small molecular mass differences of proteins by mass spectrometry

This study was undertaken to determine if acidic or basic fibroblast growth factor (FGF1 or FGF2) or vascular endothelial growth factor (VEGF) alters the radiation response of small bowel after total-body irradiation (TBI). Female C3H mice were treated with various doses of angiogenic growth factor administered intravenously 24 h before or 1 h after TBI. Radiation doses ranged from 7 to 18 Gy. End points measured were the number of crypts in three portions of the small bowel, the frequency of apoptosis of crypt cells at various times after TBI, and the LD50/30 (bone marrow syndrome) and LD50/6 (GI syndrome). Fibroblast growth factors alone, without TBI, decreased the number of crypts per circumference significantly. Among the factors tested, FGF2 caused the greatest decline in baseline crypt number. Despite this decrease in the baseline crypt number, after irradiation the number of surviving crypts was greater in animals treated with growth factor. The greatest radioprotection occurred at intermediate doses of growth factor (6 to 18 pg/mouse). Mice treated with FGF1 and FGF2 had crypt survival curves with a slope that was more shallow than that for saline-treated animals, indicating radiation resistance of crypt stem cells in FGF-treated mice. The LD50/6 was increased by approximately 10% for all treatments with angiogenic growth factors, whether given before or after TBI. Apoptosis of crypt cells was maximum at 4 to 8 h after TBI. The cumulative apoptosis was decreased significantly in animals treated with angiogenic growth factors, and the greatest protection against apoptosis was seen in animals treated with FGF2 prior to TBI. All three angiogenic growth factors tested were radioprotective in small bowel whether given 24 h before or 1 h after irradiation. The mechanism of protection is unlikely to involve proliferation of crypt stem cells, but probably does involve prevention of radiation-induced apoptosis or enhanced repair of DNA damage of crypt cells.     

Medication side effects in anxious patients: negative placebo responses?

Heart sounds produce an incessant noise during lung sounds recordings. This noise severely contaminates the breath sounds signal and interferes in the analysis of lung sounds. In this paper, the use of a wavelet transform domain filtering technique as an adaptive de-noising tool, implemented in lung sounds analysis, is presented. The multiresolution representations of the signal, produced by wavelet transform, are used for signal structure extraction. In addition, the use of hard thresholding in the wavelet transform domain results in a separation of the nonstationary part of the input signal (heart sounds) from the stationary one (lung sounds). Thus, the location of the heart sound noise (1st and 2nd heart sound peaks) is automatically detected, without requiring any noise reference signal. Experimental results have shown that the implementation of this wavelet-based filter in lung sound analysis results in an efficient reduction of the superimposed heart sound noise, producing an almost noise-free output signal. Due to its simplicity and its fast implementation the method can easily be used in clinical medicine.     

Localization of the human phosphotyrosine phosphatase-related genes (h-PRL-1) to chromosome bands 1p35-p34, 17q12-q21, 11q24-q25 and 12q24

The h-PRL-1 gene codes for a new phosphotyrosine phosphatase that may play an important role in the control of basic cellular processes such as cell growth and proliferation. Using the cDNA of the h-PRL-1 gene as a probe, we examined a somatic mouse and hamster x human hybrid panel and found that chromosomes 1, 17 and 11 harbor sequences homologous to h-PRL-1. By in situ hybridization of metaphase spreads, subchromosomal localizations were determined at bands 1p35-p34, 17q12-q21 and 11q24-q25; in addition, a faint signal was detected at 12q24. The chromosomal assignment of the genes homologous to h-PRL-1 will help the investigation of its possible involvement in human diseases involving genetic alteration at these chromosomal regions.     

Capacitance studies of multilayer ensembles of InAs QDs in a GaAs matrix

Quasi-static capacitance characteristics of multilayer arrays of vertically coupled InAs quantum dots (QDs) in a GaAs matrix were analyzed on the assumption of a Gaussian energy distribution of the ground state of the QDs. An array of InAs QDs with a characteristic base size of about 20 nm and height of ～3 nm was ordered in the growth direction and had 3, 6, or 10 layers spaced by ～5 nm. It was found that, as the number of layers increases from 3 to 10, the average binding energy of the ground electron state grows from ～80 to ～120 meV and the root mean square deviation characterizing the energy distribution of the levels of this state decreases from ～30 to ～15 meV.     

S100B, a neurotropic protein that modulates neuronal protein phosphorylation, is upregulated during lesion-induced collateral sprouting and reactive synaptogenesis

Using light and electron microscopic immunocytochemistry, we examined the expression of the Ca2+-binding protein S100B in the dentate gyrus of adult rats during lesion-induced sprouting and reactive synaptogenesis. Nine days following unilateral lesioning of the entorhinal cortex, S100B was upregulated in cells primarily in the outer part of the molecular layer of the ipsilateral dentate gyrus. When examined with electron microscopy, numerous astrocytes and synapses containing S100B were identified. These data show that during lesion-induced sprouting and reactive synaptogenesis, S100B is upregulated in astrocytes and can be found in pre- and post-synaptic compartments where it might influence neuronal protein phosphorylation.     

A high-frequency shear device for testing soft biological tissues

Accurate mechanical property data obtained at large shear deformations and high frequencies are a fundamental component of realistic numerical simulations of soft tissue injury. Although many commercial systems exist for testing shear properties of viscoelastic materials with properties similar to soft biological tissue, none are capable of determining properties at high loading rates necessary for modeling soft tissue injury. Previous custom shear testing systems, though capable of high-frequency loading, indirectly measure tissue properties by using analytical corrections for inertial effects. To address these limitations, a new custom designed oscillatory shear testing apparatus (STA) capable of testing soft biological tissues in simple shear has been constructed and validated. Through a proper selection of sample thickness, direct measurement of material properties at high frequencies is achieved mechanically without analytical inertial adjustments. The complex shear modulus of three mixtures of silicone gel with viscoelastic properties in a range similar to soft biological tissue was characterized in the STA over a dynamic frequency range of 20-200 Hz and validated with a commercially available solids rheometer. The frequency-dependent complex shear modulus measurements of the STA were within 10% of the rheometer measurements for all mixtures over the entire frequency range tested. The STA represents substantive improvement over current shear testing methods by providing direct measurement of the shear behavior of soft viscoelastic material at high frequencies. Mechanical property data gained from this device will provide a more realistic basis for numerical simulations of biological structures.     

Axial strain measurements in skeletal muscle at various strain rates

A noncontact optical system using high speed image analysis to measure local tissue deformations and axial strains along skeletal muscle is described. The spatial resolution of the system was 20 pixels/cm and the accuracy was +/- 0.125 mm. In order to minimize the error associated with discrete data used to characterize a continuous strain field, the displacement data were fitted with a third order polynomial and the fitted data differentiated to measure surface strains using a Lagrangian finite strain formulation. The distribution of axial strain along the muscle-tendon unit was nonuniform and rate dependent. Despite a variation in local strain distribution with strain rate, the maximum axial strain, Exx = 0.614 +/- 0.045 mm/mm, was rate insensitive and occurred at the failure site for all tests. The frequency response of the video system (1000 Hz) and the measurement of a continuous strain field along the entire length of the structure improve upon previous noncontact optical systems for measurement of surface strains in soft tissues.