Identification of glycoprotein 330 as an endocytic receptor for apolipoprotein J/clusterin

Glycoprotein 330 (gp330) is a member of a family of endocytic receptors related to the low density lipoprotein receptor. gp330 has previously been shown to bind a number of ligands in common with its family member, the low density lipoprotein receptor-related protein (LRP). To identify ligands specific for gp330 and relevant to its localization on epithelia such as in the mammary gland, gp330-Sepharose affinity chromatography was performed. As a result, a 70-kDa protein was selected from human milk and identified by protein sequencing to be apolipoprotein J/clusterin (apoJ). Solid-phase binding assays confirmed that gp330 bound to apoJ with high affinity (Kd = 14.2 nM). Similarly, gp330 bound to apoJ transferred to nitrocellulose after SDS-polyacrylamide gel electrophoresis. LRP, however, showed no binding to apoJ in either type of assay. The binding of gp330 to apoJ could be competitively inhibited with excess apoJ as well as with the gp330 ligands apolipoprotein E, lipoprotein lipase, and the receptor-associated protein, a 39-kDa protein that acts to antagonize binding of all known ligands for gp330 and LRP. Several cultured cell lines that express gp330 and ones that do not express the receptor were examined for their ability to bind and internalize 125I-apoJ. Only cells that expressed gp330 endocytosed and degraded radiolabeled apoJ. Furthermore, F9 cells treated with retinoic acid and dibutyryl cyclic AMP to increase expression levels of gp330 displayed an increased capacity to internalize and degrade apoJ. Cellular internalization and degradation of radiolabeled apoJ could be inhibited with unlabeled apoJ, receptor-associated protein, and gp330 antibodies. The results indicate that gp330 but not LRP can bind to apoJ in vitro and that gp330 expressed by cells can mediate apoJ endocytosis leading to lysosomal degradation.     

A least mean square error synthesis with pattern constraints atmultiple frequencies

The pattern synthesis techinque described allows the power pattern to be optimized in a very useful sense over the desired operating band of the antenna array. This is an improvement over previous techniques involving constraints on such artificial parameters as source norm and superdirectivity ratio, which do not, in fact, ensure a useful pattern bandwidth. The procedure described provides minimum mean square error over an arbitrary number of discrete frequencies     

Tumor detection in nonstationary backgrounds

The authors introduce two detectors which they use to locate simulated tumors of fixed size in clinical gamma-ray images. The first method was conceived when it was observed that small tumors possess an identifiable signature in curvature feature space, where "curvature" is the local curvature of the image data when viewed as a relief map. Computed curvature values are mapped to a normalized significance space using a windowed statistic. The resulting test statistic is thresholded at a chosen level of significance to give a positive detection. Nonuniform anatomic background activity is effectively suppressed. The second detector is an adaptive prewhitening matched filter, which uses a form of preprocessing known as statistical scaling to adaptively prewhiten the background. Tests are performed using simulated Gaussian-shaped tumors superimposed on twelve clinical gamma ray images. When the tumors to be detected are small-less than 3 pixels in diameter-the curvature detector out-performs the matched filter in true positive/false positive tests. A mean true positive rate of 95% at one false positive per image is achieved when the local signal-to-noise ratio of the tumor-background is >/=2. At larger tumor sizes the best performance is displayed by a different form of matched filter, namely the statistical correlation function proposed by Pratt (1991).     

Wavelet transforms for detecting microcalcifications in mammograms

Clusters of fine, granular microcalcifications in mammograms may be an early sign of disease. Individual grains are difficult to detect and segment due to size and shape variability and because the background mammogram texture is typically inhomogeneous. The authors develop a 2-stage method based on wavelet transforms for detecting and segmenting calcifications. The first stage is based on an undecimated wavelet transform, which is simply the conventional filter bank implementation without downsampling, so that the low-low (LL), low-high (LH), high-low (HL), and high-high (HH) sub-bands remain at full size. Detection takes place in HH and the combination LH+HL. Four octaves are computed with 2 inter-octave voices for finer scale resolution. By appropriate selection of the wavelet basis the detection of microcalcifications in the relevant size range can be nearly optimized. In fact, the filters which transform the input image into HH and LH+HL are closely related to prewhitening matched filters for detecting Gaussian objects (idealized microcalcifications) in 2 common forms of Markov (background) noise. The second stage is designed to overcome the limitations of the simplistic Gaussian assumption and provides an accurate segmentation of calcification boundaries. Detected pixel sites in HH and LH+HL are dilated then weighted before computing the inverse wavelet transform. Individual microcalcifications are greatly enhanced in the output image, to the point where straightforward thresholding can be applied to segment them. FROG curves are computed from tests using a freely distributed database of digitized mammograms.     

Circular cross-polarization measurements on earth-space paths at 11,7 GHz

Rain and icecrystal depolarization measurements were made on earthspace paths at four locations across Canada using the circularlypolarized 11.7 GHz beacon transmission from the cts satellite. Results show that when rain is the dominant depolarization mechanism, crosspolarization discrimination (xpd)is statistically related to copolar attenuation (cpa)according to xpd =U?20 log cpa with U showing improvement with increasing elevation angle. Icecrystal depolarization events, with accompanying differential phase shifts as large as 20°, were also observed. An analysis separating these events from the data demonstrates that at 11.7 GHz icecrystal depolarization degrades xpd statistics by less than 1 dB at the small percentages of time.     

Symbol synchronization using signal samples and interpolation

A method for symbol synchronization using two unsynchronized signal samples per symbol is presented. Signal values between the sample points are calculated by interpolation and then processed digitally to find a suitable strobe point. The interpolated value at the strobe point is used for data detection or input to an equalizer. Simulations show that low variance timing estimates can be made for pulses with raised-cosine spectra degraded by quadratic delay distortion     

US EPA's acute reference exposure methodology for acute inhalation exposures

The US Environmental Protection Agency (EPA) National Center for Environmental Assessment is engaged in the development of a methodology for Agency use to perform risk assessments for non-cancer effects due to acute inhalation exposures. The methodology will provide general guidance for deriving chemical-specific acute exposure benchmarks called acute reference exposures (AREs). Chemical-specific AREs are analogous to reference concentra tions (RfCs) for chronic non-cancer effects and will be incorporated in chemical-specific files in the US EPA's Integrated Risk Information System (IRIS) as they are developed and reviewed. AREs will have wide applicability in assessing the potential health risks of accidental and routine acute releases of chemicals to the environment. The proposed methodology for ARE development provides a framework for choosing an optimal derivation approach, depending on the type of data available, from the no-observed-adverse-effect level (NOAEL), benchmark concentration (BMC), or categorical regression approaches. Uncertainty factors are applied to the point of departure, determined by one of the recommended approaches, to derive the ARE. Due to the capability to use more exposure-response information than the NOAEL approach allows, exposure-response analyses such as BMC and categorical regression are favored as methods to develop the point of departure when the available database will support such analyses. The NOAEL approach is suitable when the data are insufficient to support exposure-response modeling. Applications of the proposed ARE methodology are illustrated by the derivation of example AREs for hydrogen sulfide and hexachlorocyclopentadiene, which showcase the categorical regression and NOAEL approaches, respectively. In addition, a recent review of the proposed ARE methodology by the US EPA Risk Assessment Forum is discussed.