Characterizing the relationship between gonadotropin releasing hormone (GnRH), kisspeptin, and RFamide related peptide 3 (RFRP-3) neurons in the equine hypothalamus across the estrous cycle and in the anovulatory seasons

To understand better the role that kisspeptin plays in regulating seasonal and estrous cycle changes in the mare, this study investigated the number, location and interactions between GnRH, kisspeptin and RFRP-3 neurons in the equine hypothalamus. Hypothalami were collected from mares during the non-breeding season, vernal transition and various stages of the breeding season. Fluorescent immunohistochemistry was used to label the neuropeptides of interest. GnRH cells were observed primarily in the arcuate nucleus (ARC), while very few labeled cells were identified in the pre-optic area (POA). Kisspeptin cells were identified primarily in the ARC, with a small number of cells observed dorsal to the ARC, surrounding the third ventricle (3V). The mean number of kisspeptin cells varied between animals and typically showed no pattern associated with season or stage of estrous cycle, but a seasonal difference was identified in the ARC population. Small numbers of RFRP-3 cells were observed in the ARC, ventromedial hypothalamus (VMH) and dorsomedial hypothalamus (DMH). The mean number of RFRP-3 cells appeared higher in pre-ovulatory animals compared to all other stages. The percentage of GnRH cell bodies with kisspeptin appositions did not change with season or stage of estrous cycle. The percentage of kisspeptin cells receiving inputs from RFRP-3 fibers did not vary with season or stage of estrous cycle. These interactions suggest the possibility of the presence of an ultra-short loop feedback system between these three peptides. The changes in RFRP-3 neurons suggest the possibility of a role in the regulation of reproduction in the horse, but it is unlikely to be as a gonadotropin inhibitory factor.

Comparison between endocrine activity assessed using ToxCast/Tox21 database and human plasma concentration of sunscreen active ingredients/UV filters

Sunscreen products are composed of ultraviolet (UV) filters and formulated to reduce exposure to sunlight thereby lessening skin damage. Concerns have been raised regarding the toxicity and potential endocrine disrupting (ED) effects of UV filters. The ToxCast/Tox21 program, that is, CompTox, is a high-throughput in vitro screening database of chemicals that identify adverse outcome pathways, key events, and ED potential of chemicals. Using the ToxCast/Tox21 database, octisalate, homosalate, octocrylene, oxybenzone, octinoxate, and avobenzone, 6 commonly used organic UV filters, were found to have been evaluated. These UV filters showed low potency in these bioassays with most activity detected above the range of the cytotoxic burst. The pathways that were most affected were the cell cycle and the nuclear receptor pathways. Most activity was observed in liver and kidney-based bioassays. These organic filters and their metabolites showed relatively weak ED activity when tested in bioassays measuring estrogen receptor (ER), androgen receptor (AR), thyroid receptor, and steroidogenesis activity. Except for oxybenzone, all activity in the endocrine assays occurred at concentrations greater than the cytotoxic burst. Moreover, except for oxybenzone, plasma concentrations (Cmax) measured in humans were at least 100× lower than bioactive (AC50/ACC) concentrations that produced a response in ToxCast/Tox21 assays. These data are consistent with in vivo animal/human studies showing weak or negligible endocrine activity. In sum, when considered as part of a weight-of-evidence assessment and compared with measured plasma concentrations, the results show these organic UV filters have low intrinsic biological activity and risk of toxicity including endocrine disruption in humans.

Sex differences in the expression of estrogen receptor alpha within noradrenergic neurons in the sheep brain stem

In female sheep, high levels of estrogen exert a positive feedback action on gonadotropin releasing hormone (GnRH) secretion to stimulate a surge in luteinizing hormone (LH) secretion. Part of this action appears to be via brain stem noradrenergic neurons. By contrast, estrogen action in male sheep has a negative feedback action to inhibit GnRH and LH secretion. To investigate whether part of this sex difference is due to differences in estrogen action in the brain stem, we tested the hypothesis that the distribution of estrogen receptor α (ERα) within noradrenergic neurons in the brain stem differs between rams and ewes. To determine the distribution of ERα, we used double-label fluorescence immunohistochemistry for dopamine β-Hydroxylase, as a marker for noradrenergic and adrenergic cells, and ERα. In the ventrolateral medulla (A1 region), most ERα-immunoreactive (-ir) cells were located in the caudal part of the nucleus. Overall, there were more ERα-ir cells in rams than ewes, but the proportion of double-labeled cells was did not differ between sexes. Much greater numbers of ERα-ir cells were found in the nucleus of the solitary tract (A2 region), but <10% were double labeled and there were no sex differences. The majority of ERα-labeled cells in this nucleus was located in the more rostral areas. ERα-labeled cells were found in several rostral brain stem regions but none of these were double labeled and so were not quantified. Because there was no sex difference in the number of ERα-ir cells in the brain stem that were noradrenergic, the sex difference in the action of estrogen on gonadotropin secretion in sheep is unlikely to involve actions on brain stem noradrenergic cells.

Mode perturbation method for optimal guided wave mode and frequency selection

With a thorough understanding of guided wave mechanics, researchers can predict which guided wave modes will have a high probability of success in a particular nondestructive evaluation application. However, work continues to find optimal mode and frequency selection for a given application. This "optimal" mode could give the highest sensitivity to defects or the greatest penetration power, increasing inspection efficiency. Since material properties used for modeling work may be estimates, in many cases guided wave mode and frequency selection can be adjusted for increased inspection efficiency in the field. In this paper, a novel mode and frequency perturbation method is described and used to identify optimal mode points based on quantifiable wave characteristics. The technique uses an ultrasonic phased array comb transducer to sweep in phase velocity and frequency space. It is demonstrated using guided interface waves for bond evaluation. After searching nearby mode points, an optimal mode and frequency can be selected which has the highest sensitivity to a defect, or gives the greatest penetration power. The optimal mode choice for a given application depends on the requirements of the inspection.

Hepatocyte growth factor inhibits epithelial to myofibroblast transition in lung cells via Smad7

Idiopathic pulmonary fibrosis is a lethal parenchymal lung disease characterized by denudation of the lung epithelium, fibroblast proliferation, and collagen deposition. Cellular changes underlying disease progression involve injury to alveolar epithelial cells, epithelial to mesenchymal transition, proliferation of alpha-smooth muscle actin (alpha-SMA)-expressing myofibroblasts and of fibroblasts resulting in enhanced deposition of extracellular matrix proteins. Hepatocyte growth factor (HGF) inhibits progression of bleomycin-induced pulmonary fibrosis in mice. The mechanism underlying the inhibitory effect of HGF was investigated in an in vitro model. We show that HGF markedly antagonizes basal and transforming growth factor (TGF)-beta-induced expression of myofibroblast markers such as alpha-SMA, collagen type 1, and fibronectin in rat alveolar epithelial cells. HGF also inhibited TGF-beta-induced alpha-SMA expression in primary murine alveolar epithelial cells. Since TGF-beta is known to regulate alpha-SMA expression, the effect of HGF on components of TGF-beta signaling was investigated. HGF induced expression of Smad7, an inhibitor of TGF-beta signaling, in a mitogen-activated protein kinase-dependent manner. HGF also induced the nuclear export of Smad7 and Smad ubiquitin regulatory factor 1 (Smurf1) to the cytoplasm. HGF-dependent decrease in alpha-SMA was abolished with specific siRNAs targeted to Smad7. Thus, induction of Smad7 by HGF serves to limit acquisition of the myofibroblast phenotype in alveolar epithelial cells.

Sensitivity of mice to lipopolysaccharide is increased by a high saturated fat and cholesterol diet

Background

It was hypothesized that a pro-atherogenic, high saturated fat and cholesterol diet (HCD) would increase the inflammatory response to E. coli endotoxin (LPS) and increase its concentration in plasma after administration to mice.

Methods

C57Bl/6 mice were fed a HCD or a control diet (CD) for 4 weeks, and then treated with saline, 0.5, 1 or 2 mg LPS/kg, ip. Liver injury (alanine:2-oxoglutarate aminotransferase and aspartate aminotransferase, collagen staining), circulating cytokines (tumor necrosis factor-α, interleukin-6 and interferon-γ), factors that can bind LPS (serum amyloid A, apolipoprotein A1, LPS binding protein, and CD14), and plasma levels of LPS were measured. The hepatic response was assessed by measuring vascular cell adhesion molecule (VCAM)-1, inducible nitric oxide synthase (iNOS) and signal transducer and activator of transcription-1 proteins, and VCAM-1 and iNOS mRNAs. Hepatic mRNA encoding the LPS receptor, Toll like receptor 4, was also determined.

Results

Two mg LPS/kg killed 100% of mice fed HCD within 5 d, while no mice fed CD died. All mice treated with 0 to 1 mg LPS/kg survived 24 h. HCD increased plasma alanine:2-oxoglutarate aminotransferase and aspartate aminotransferase, and the enzymes were increased more by LPS in HCD than CD mice. Induction of plasma tumor necrosis factor-α, interleukin-6, and interferon-γ by LPS was greater with HCD than CD. Hepatic VCAM-1 and iNOS protein and mRNA were induced by LPS more in mice fed HCD than CD. Tyrosine phosphorylation of signal transducer and activator of transcription-1 caused by LPS was prolonged in HCD compared with CD mice. Despite the hepatic effects of HCD, diet had no effect on the LPS plasma concentration-time profile. HCD alone did not affect circulating levels of plasma apolipoprotein A1 or LPS binding protein. However, plasma concentrations of serum amyloid A and CD14, and hepatic toll-like receptor-4 mRNA were increased in mice fed HCD.

Conclusion

HCD increased the sensitivity of mice to LPS without affecting its plasma level. Although increased serum amyloid A and CD14 in the circulation may inhibit LPS actions, their overexpression, along with hepatic toll-like receptor-4 or other factors, may contribute to the heightened sensitivity to LPS.

Base excision repair proteins are required for integrin-mediated suppression of bleomycin-induced DNA breakage in murine lung endothelial cells

Engagement of integrin cell adhesion receptors suppresses bleomycin (BLM)-induced DNA strand breakage in endothelial cells. Previous investigation of cells from poly(ADP-ribose) polymerase (PARP)-1 knockout mice and with an inhibitor of the enzyme indicated that this facilitator of base excision repair (BER) is required for integrin-mediated suppression of DNA strand breakage. Here, small inhibitory RNA (siRNA) was used to assess the requirement for the BER proteins, DNA ligase III (Lig3) alpha, PARP-1, and X-ray repair complementing defective repair in Chinese hamster cells 1 (XRCC1), and for the long-patch BER ligase, DNA ligase I (Lig1), in integrin-mediated protection from BLM-induced DNA breakage. Murine lung endothelial cells (MLECs) were transfected with siRNA, treated with anti-beta1 integrin antibody, and then BLM. 3'-OH in DNA and accumulation of phosphorylated histone H2AX (gammaH2AX), which reflects double-strand breakage, were measured. Integrin antibody inhibited the increases in 3'-OH caused by BLM in MLECs transfected with either control or Lig1 siRNA. However, after knockdown of Lig3alpha, PARP-1, or XRCC1, suppression of DNA breakage by integrin antibody was limited. BLM increased gammaH2AX levels, and integrin treatment inhibited this by 57 to 73% in MLECs transfected with control siRNA. Integrin engagement also inhibited increases in gammaH2AX in BLM-treated cells transfected with Lig1 siRNA. In contrast, Lig3alpha, PARP-1, and XRCC1 siRNAs prevented integrin-mediated inhibition of BLM-induced gammaH2AX levels. The results suggest that the BER proteins, Lig3alpha, PARP-1, and XRCC1, are required for integrin-mediated suppression of BLM-induced DNA breakage.

Integrin engagement increases histone H3 acetylation and reduces histone H1 association with DNA in murine lung endothelial cells

Engagement of integrin cell adhesion receptors in mouse lung endothelial cells induces global sensitivity of DNA to nuclease digestion, reflecting alterations in chromatin structure. These structural changes may contribute to the antigenotoxic effects of integrin engagement in lung endothelium. Because histone acetylation and poly(ADP-ribosyl)ation modulate chromatin structure, we investigated the effects of beta1 integrin engagement with antibody on these post-translational modifications and the presence of histones at discrete DNA sequences in the mouse lung endothelial cell genome using chromatin immunoprecipitation. Integrin engagement increased acetylation of core histone H3. The presence of acetylated histone H3 at intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) promoters, and a nonpromoter sequence was also increased. As with integrin engagement, the histone deacetylase inhibitor trichostatin A caused global hypersensitivity of DNA to nuclease digestion and induced acetylation of histone H3 and its coimmunoprecipitation with VCAM-1 and ICAM-1 promoters and nonpromoter DNA. In contrast to acetyl-histone H3, the association of linker histone H1 with specific DNA sequences was either reduced or unaffected by integrin engagement and trichostatin A. Although integrin engagement and trichostatin A treatment did not affect histone H1 poly(ADP-ribosyl)ation, deletion of poly(ADP-ribose) polymerase-1 increased core histone H3 acetylation and increased its level at the iNOS promoter while decreasing the amount of histone H1. The results suggest that integrin engagement, as well as trichostatin A and PARP-1 deletion, regulate chromatin structure via core histone H3 acetylation and reduced linker histone H1-DNA association.

p38 Mitogen-activated protein kinase mediates synergistic induction of inducible nitric-oxide synthase by lipopolysaccharide and interferon-gamma through signal transducer and activator of transcription 1 Ser727 phosphorylation in murine aortic endothelial cells

Nitric oxide (NO) can be produced in large amounts by up-regulation of inducible NO synthase (iNOS). iNOS is induced in many cell types by pro-inflammatory agents, such as bacterial lipopolysaccharide (LPS) and cytokines. Overproduction by endothelial cells (EC) may contribute to vascular diseases. In contrast to macrophages, murine aortic endothelial cells (MAEC) produced no NO in response to either LPS or interferon gamma (IFNgamma), whereas combined treatment was highly synergistic. In this study, we investigated the mechanisms of synergy in MAEC. LPS activated p38 mitogen-activated protein kinase (MAPK), whereas IFNgamma activated Janus kinase and signal transducer and activator of transcription-1 (STAT1). Both pathways were required for iNOS induction because herbimycin A, a tyrosine kinase inhibitor, and 4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)1H-imidazole. HCl (SB202190), a p38 MAPKalpha/beta inhibitor, each blocked induction. LPS increased the phosphorylation of STAT1alpha at serine 727 in IFNgamma-treated MAEC. SB202190, but not 2'-amino-3'-methoxyflavone (PD98059), an inhibitor of p44/p42 MAPK activation, abolished the phosphorylation and induction of iNOS. SB202190 did not affect tyrosine 701 phosphorylation or nuclear translocation of STAT1. However, STAT1-DNA binding activity was reduced by SB202190. Although LPS stimulated the DNA binding activity of nuclear factor kappaB and activating protein-1, combined treatment with IFNgamma did not enhance activation, and SB202190 did not inhibit it. The results indicate that p38 MAPKalpha and/or beta are required for the synergistic induction of iNOS by LPS and IFNgamma in MAEC. Furthermore, the synergistic induction is associated with phosphorylation of STAT1alpha serine 727 in MAEC. This observation may explain potentially beneficial effects of p38 MAPK inhibitors in vascular inflammatory diseases.

Implementing guided wave mode control by use of a phased transducer array

A multi-channel time-delay system has been built and applied to a transducer array for implementing guided wave mode control. The time-delay system has a capability of sending high energy controllable tone-burst signals from eight independent channels with arbitrary time delays from 0 to 30 microseconds with resolution of 0.025 microsecond. Software time delays are also provided for summing up received signals of each channel. Theoretical discussions indicate the impact of the time delay capability on the bandwidth and sensitivity improvement of a transducer array for guided wave generation. Determination of both physical and software time delay values is based on a knowledge of dispersion curves and element spacing. Based on reference signals, a non-knowledge-based automatic time-delay searching algorithm was introduced for guided wave mode selection. Experiments were conducted with a phased comb transducer array mounted on a carbon steel pipe. The experimental results show that signal to noise ratio has been greatly improved by use of the time-delay system. Some other benefits of the phased array, including unidirection generation and mode control flexibility, are discussed.

Guided wave nuances for ultrasonic nondestructive evaluation

Recent developments in guided wave generation, reception, and mode control show that increased penetration power and sensitivity are possible. A tone burst function generator and appropriate signal processing are generally used. Variable angle beam and comb-type transducers are the key to this effort. Problems in tubing, piping, hidden corrosion detection in aging aircraft, adhesive and diffusion bonding, and ice detection are discussed. Additionally, sample configurations, inspection objectives, and logic are being developed for such sample problems as defect detection and analysis in lap splice joints, tear straps, cracks in a second layer, hidden corrosion in multiple layers, cracks from rivet holes, transverse cracking in a beam, and cracks in landing gear assembly. Theoretical and experimental aspects of guided wave analysis include phase velocity, group velocity, and attenuation dispersion curves; boundary element model analysis for reflection and transmission factor analysis; use of wave structure for defect detection sensitivity; source influence on the phase velocity spectrum, and the use of angle beam and comb transducer technology. Probe design and modeling considerations are being explored. Utilization of in-plane and out-of-plane displacement patterns on the surface and longitudinal power distribution across the structural cross-section are considered for improved sensitivity, penetration power, and resolution in nondestructive evaluation. Methods of controlling the phase velocity spectrum for mode and frequency selection are available. Such features as group velocity change, mode cut-off measurements, mode conversion, amplitude ratios of transmission, and reflection factors of specific mode and frequency as input will be introduced for their ability to be used in flaw and material characterization analysis.

Mirizzi syndrome: A rare cause of obstructive jaundice

Mirizzi syndrome is a rare cause of bile duct obstruction secondary to extrinsic compression of the hepatic duct by stones impacted in the cystic duct or infundibulum of the gallbladder. The suspicion of Mirizzi syndrome primarily relies on radiographic means such as ultrasound, computed tomography and cholangiography. The recognition of this rare syndrome is crucial in developing the proper treatment approach. We present 3 cases of Mirizzi syndrome and a review of the literature pertaining to the diagnosis and treatment of this rare cause of obstructive jaundice.

Guided waves by axisymmetric and non-axisymmetric surface loading on hollow cylinders

Guided waves generated by axisymmetric and non-axisymmetric surface loading on a hollow cylinder are studied. For the theoretical analysis of the superposed guided waves, a normal mode concept is employed. The amplitude factors of individual guided wave modes are studied with respect to varying surface pressure loading profiles. Both theoretical and experimental focus is given to the guided waves generated by both axisymmetric and non-axisymmetric excitation. For the experiments, a comb transducer and high power tone burst function generator system are used on a sample Inconel tube. Surface loading conditions, such as circumferential loading angles and axial loading lengths, are used with the frequency and phase velocity to control the axisymmetric and non-axisymmetric mode excitations. The experimental study demonstrates the use of a practical non-axisymmetric partial loading technique in generating axisymmetric modes, particularly useful in the inspection of tubing and piping with limited circumferential access. From both theoretical and experimental studies, it also could be said that the amount of flexural modes reflected from a defect contains information on the reflector's circumferential angle, as well as potentially other classification and sizing feature information. The axisymmetric and non-axisymmetric guided wave modes should both be carefully considered for improvement of the overall analysis of guided waves generated in hollow cylinders.

Socs1 binds to multiple signalling proteins and suppresses steel factor-dependent proliferation

We have identified Socs1 as a downstream component of the Kit receptor tyrosine kinase signalling pathway. We show that the expression of Socs1 mRNA is rapidly increased in primary bone marrow-derived mast cells following exposure to Steel factor, and Socs1 inducibly binds to the Kit receptor tyrosine kinase via its Src homology 2 (SH2) domain. Previous studies have shown that Socs1 suppresses cytokine-mediated differentiation in M1 cells inhibiting Janus family kinases. In contrast, constitutive expression of Socs1 suppresses the mitogenic potential of Kit while maintaining Steel factor-dependent cell survival signals. Unlike Janus kinases, Socs1 does not inhibit the catalytic activity of the Kit tyrosine kinase. In order to define the mechanism by which Socs1-mediated suppression of Kit-dependent mitogenesis occurs, we demonstrate that Socs1 binds to the signalling proteins Grb-2 and the Rho-family guanine nucleotide exchange factors Vav. We show that Grb2 binds Socs1 via its SH3 domains to putative diproline determinants located in the N-terminus of Socs1, and Socs1 binds to the N-terminal regulatory region of Vav. These data suggest that Socs1 is an inducible switch which modulates proliferative signals in favour of cell survival signals and functions as an adaptor protein in receptor tyrosine kinase signalling pathways.

Lamb wave generation and reception with time-delay periodic linear arrays: a BEM simulation and experimental study

A time-delay periodic linear array model has been proposed for Lamb wave generation and reception in plates. The unilateral guided wave emitting and receiving have been achieved by applying the interference principle in the array designs. A hybrid BEM technique has been developed and applied to simulate the wave generation procedure with such arrays and to analyze the performance. Experimental results also are presented for two typical time-delay periodic arrays to qualitatively validate the theoretical designs. The effects of the array parameters on the array performance, such as the selectivity of Lamb modes and effectiveness of Lamb wave generation, are investigated through the 2-D phase velocity-frequency spectrum analyses as well as Lamb mode wave structure calculations.

Perception-action coupling in the development of visual control of posture

In this investigation of developmental changes in the coordination of perceived optical flow and postural responses, 4 age groups of infants (5-, 7-, 9-, and 13-month-olds) were tested while seated on a force plate in a "moving room." During each trial the walls oscillated in an anteroposterior direction for 12 s, and the postural sway of the infant was measured. The results revealed that infants perceived the frequency and amplitude of the optical flow and scaled their postural responses to the visual information. This scaling was present even before infants could sit without support, but it showed considerable improvement during the period when infants learn to sit. Taken together, these results suggest that the visuomotor coordination necessary for controlling sitting is functional prior to the onset of independent sitting but becomes more finely tuned with experience.

Perception-action coupling in the development of visual control of posture

In this investigation of developmental changes in the coordination of perceived optical flow and postural responses, 4 age groups of infants (5-, 7-, 9-, and 13-month-olds) were tested while seated on a force plate in a "moving room." During each trial the walls oscillated in an anteroposterior direction for 12 s, and the postural sway of the infant was measured. The results revealed that infants perceived the frequency and amplitude of the optical flow and scaled their postural responses to the visual information. This scaling was present even before infants could sit without support, but it showed considerable improvement during the period when infants learn to sit. Taken together, these results suggest that the visuomotor coordination necessary for controlling sitting is functional prior to the onset of independent sitting but becomes more finely tuned with experience.

Lamb wave scattering analysis for reflector characterization

The potential use of guided waves for defect characterization is studied. The influence of defect shape and size on transmitted and reflected fields is considered. Using the hybrid boundary element technique, the reflection and transmission coefficients for selected guided wave modes are numerically calculated and compared to experimental data. Selecting the aspect ratio as a shape parameter for various defects, the transmission and reflection coefficients are measured for certain guided wave modes input to the defect. The influence of defect size is then studied by monitoring the transmission and reflection coefficients for defects of various shapes and depths. The studies presented indicate that defect characterization is possible if a proper mode selection criteria can be established. The suitable features related to transmission and reflection coefficient data can also be used for algorithm development and implementation purposes of defect characterization.

Maternal influences on milk intake in SHR and WKY pups

Mother to pup milk transfer was examined in the spontaneously hypertensive rat (SHR) and its normotensive progenitor, the Wistar-Kyoto (WKY). Litters of SHR and WKY pups were either reared by their natural mothers or cross-fostered to mothers of the opposite strain shortly after birth. At postpartum days 7 and 14, pup body weights were monitored throughout a 2-h maternal separation period followed by a 3-h refeeding period during which pups remained with their mothers. Weight increases of pups over the refeeding period served as an indirect measure of milk ingestion. At postpartum day 7, both SHR and WKY pups nursed by SHR mothers received lower quantities of milk compared to their counterparts nursed by WKY mothers. Maternal strain differences in milk transfer were largely attenuated at postpartum day 14. The different nutritional environments provided by SHR and WKY mothers may mediate the alterations in offspring cardiovascular physiology and physical development that occur with reciprocal cross-fostering.

A computer model for simulating ultrasonic scattering in biological tissues with high scatterer concentration

Scattering of ultrasonic waves by biological tissues at different scatterer concentrations is investigated using one- and two-dimensional computer simulation models. The backscattered power as a function of scatterer concentrations is calculated using two types of incident waves, a Gaussian shaped pulse and a continuous wave (CW). The simulation results are in good agreement with the Percus-Yevick packing theory within the scatterer concentrations, from 0% to 100% in one-dimensional (1D) space, and 0% to 46% in two-dimensional (2D) space. In all cases, the simulation results from a pulsed incident wave show a much smaller standard deviation (SD) than those from an incident CW. The simulation can serve as a useful tool to verify scattering theories, simulate different experimental conditions, and to investigate the interaction between the scatterer properties and the scattering of ultrasonic waves. More importantly, the 2D simulation procedure serves as an initial step toward the final realization of a true three-dimensional (3D) simulation of ultrasonic scattering in biological tissues.

Yield improvement in soybeans using recurrent selection

The objective of this study was to evaluate the potential of recurrent selection for improving seed yield in a soybean population. Seventeen parents, chosen for their high yield potential in the sub-tropical environments of Southern and Central Queensland were intermated using a diallel cross mating system. F1 plants were intercrossed in pairs for two more generations and then allowed to self for two generations to produce the base population. The selection criterion was the seed yield of S1 lines grown at Hermitage Research Station. The selection intensity was approximately 10%. After five cycles of recurrent selection the mean yield of the population and the mean yield of the lines selected for recombination had improved by 17% and 54% respectively, in comparison with one of the original parents, Davis. Progress from recurrent selection was evaluated using fifty randomly selected lines from the base population and from each of the first three cycles of selection. The average gain per cycle in seed yield, averaged over five sites was 128 kg ha-1 or 5.4% of the yield of the base population. Greater progress (9.8% per cycle) was measured at the testing site for selection (Hermitage Research Station) which was heavily infested with phytophthora root and stem rot than at three other sites (2.7% per cycle) which has nil or low levels of disease. Broad sense heritabilities for the base population and for cycles 1, 2 and 3 in the evaluation trial were 0.34, 0.25, 0.13 and 0.14 respectively compared with a mean heritability of 0-64 for the first five cycles of the selection experiment. Expected gain from further cycles of selection was estimated at 102 kg ha-1 per cycle for three replicates at a single site. In the evaluation trial correlated responses to selection for yield were found in a number of other traits. Days to flowering was reduced by 0.8 days/cycle while days to maturity increased by 1 day/cycle. Seed shattering score was significantly reduced from 0.98 to 0-69 while there were only minor changes in plant height, lodging and seed coat quality score. Resistance to root and stem rot and seed coat mottling, due to primarily to soybean mosaic virus, were also significantly increased. The improvement in phytophthora resistance was expected as the field used for S1 yield testing had become infested with the disease. A covariate analysis indicated that about half the improvement in seed yield at the Hermitage site was due to the correlated response of increased resistance to phytophthora root and stem rot.

Split-spectrum processing: analysis of polarity threshold algorithm for improvement of signal-to-noise ratio and detectability in ultrasonic signals

A polarity thresholding algorithm that has recently been developed for split-spectrum processing for ultrasonic coherent noise reduction is theoretically analyzed to evaluate its performance. The probability density function (PDF) of the output of the algorithm is derived and used to calculate the theoretical signal-to-noise ratio (SNR) enhancement and the receiver operating characteristics. The performance limits of the algorithm are also established. Some experimental results of SNR enhancement obtained with the polarity thresholding algorithm are presented.

Ultrasonic tissue characterization of fetal lung, liver, and placenta for the purpose of assessing fetal maturity

The purpose of this research effort was to establish a physical basis for the development of an accurate noninvasive technique to differentiate between mature and immature fetal tissues, particularly the lung and placenta. The research utilized RF waveform analysis via a microcomputer-based digital processing system interfaced directly to a standard real-time clinical diagnostic ultrasound instrument. Differences between the frequency spectra of the RF waveforms for mature and immature fetal tissues could be demonstrated in accordance with proposed tissue models.

Characterization of benign and malignant tissues of the thyroid gland. An ultrasonic approach using RF waveform analysis and pattern recognition

A physical basis was developed for an accurate noninvasive technique to differentiate malignant thyroid tumors from benign lesions based upon a frequency-dependent attenuation model. The research effort utilized RF waveform analysis via a minicomputer based digital processing system. Data collection was performed using a standard clinical B-Mode diagnostic instrument with a transducer specially designed for imaging the thyroid gland. Differences between the frequency spectra of the RF waveforms for benign and malignant pathologies could be demonstrated in accordance with the proposed model.

Effects of systemic fungicidal seed dressings on the incidence of Phytophthora megasperma, nodulation, and nitrogen fixation in two soybean cultivars

Two cultivars of soybeans, Davis and Ross, resistant and susceptible to Phytophthora root rot, respectively, were grown in a field trial where there was a moderately high level of Phytophthora megasperma f. sp. glycinea. The efficacy of metalaxyl and Dowco 444 as fungicidal seed dressings, their interaction with host resistance and the effect of plant health on nodulation and nitrogen fixing activity (acetylene reduction) were assessed. The cultivar Davis showed a relatively high level of field resistance in the absence of fungicidal protection; this was manifest in increased emergence and a lower incidence of disease in the surviving plants. In contrast cv. Ross had virtually no field resistance. In both cultivars, disease incidence was lower where fungicides were used. Metalaxyl was more effective than Dowco 444 on cv. Ross but not on cv. Davis. This suggests that the better performance of Dowco 444 on Davis was through an enhancement of existing resistance mechanisms of the host. Nitrogen fixing activity was generally higher in Davis than in Ross with a positive correlation between nitrogen fixing activity and nodule number. Disease incidence was negatively correlated with nitrogen fixing activity indicating the dependence of nitrogen fixation on root health. Neither fungicides suppressed nitrogen fixing activity at the rates used.

Application of pattern recognition techniques to breast cancer detection: ultrasonic analysis of 100 pathologically confirmed tissue areas

Ultrasonic pulse-echo rf waveform analysis and selected pattern recognition methods were applied to classification of breast tissue. Emphasis was placed on the classification of solid tissue areas since fluid areas are easily identified by present B-scan techniques.

Pattern recognition techniques such as the Fisher Linear Discriminant (FLD), Probability Density Function (PDF) curves, jackknife estimate and committee vote were used to construct and evaluate a two class algorithm, malignant versus benign tissue areas. A data base consisting of frequency domain features from 100 pathologically confirmed tissue areas from 87 patients were used to train the algorithm. Algorithm performance was acquired via the generalized jackknife procedure to significantly reduce the bias frequently encountered in algorithm evaluation. Estimated values of algorithm performance are sensitivity and specificity values of 96 percent and 68 percent, respectively.

Reaction of soybean cultivars to races of Phytophthora megasperma f.sp. glycinea present in Queensland

Phytophthora megasperma f.sp, glycinea, the cause of phytophthora root and stem rot of soybeans, was found to be widespread in southern Queensland. Race determinations on 56 isolates were made at 26�C using the North American differential set. Thirty isolates resembled race 1 (virulent only on Harosoy), while the remaining isolates killed varying proportions of the other six differentials. Two of these isolates most closely resembled race 15. When race determinations were repeated for four isolates at 31�C, each isolate was more virulent on most of the differentials. One isolate resembling race 1 at 26�C would have been classified as race 2 at 31�C. All of the cultivars grown in Queensland were susceptible to hypocotyl inoculation, indicating the absence of genes conditioning resistance to races 1 and 15. Small proportions of plants in some cultivars, including Davis and Bragg were resistant to hypocotyl inoculation. The field resistances of 21 cultivars and breeding lines were assessed in a disease nursery. Progressive assessments of disease incidence were significantly correlated with grain yield and plant height. Davis had the highest level of field resistance while Ross and Semstar had the lowest. A breeding line (HS 1115) was identified as highly resistant to the fungus, both in the field and following hypocotyl inoculation. Three F6 lines from the cross Davis x Bragg showed a range of disease reactions, with the best showing an equivalent level of resistance to that of Davis.