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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 ß-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.

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.

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.

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.