Bistatic, above-critical angle scattering measurements of fully buried unexploded ordnance (UXO) and clutter.

Laboratory grade bistatic scattering measurements are conducted in order to examine the acoustic response of realistic fully buried unexploded ordnance (UXO) from above-critical angle insonification, between 2 and 40 kHz. A 127 mm diameter rocket UXO, a 155 mm diameter artillery shell, a natural rock of approximately the same size, and a cinder block are fully buried in water-saturated medium grained sand (mean grain diameter, 240 µm) at depths of 10 cm below the water-sediment interface. A two-dimensional array of bistatic scattering measurements is generated synthetically by scanning a single hydrophone in steps of 3 cm over a 1 m × 1 m patch directly above the targets at a height of 20 cm above the water-sediment interface. Three-dimensional volumetric acoustic images generated from the return waveforms reveal scattering components attributed to geometric and elastic scattering, as well as multiple-scattering interactions of returns between the sediment-water interface and the buried objects. The far-field target strength of the objects is estimated through extrapolation of the angular spectrum. Agreement is found between experimental data and simulated data generated from a finite-element-based, three-dimensional time-harmonic model (2-25 kHz). Separation of the measured UXO from the clutter objects is demonstrated through exploitation of structural-acoustics-based features.

Exploiting forward scattering for detecting submerged proud/half-buried unexploded ordnance.

Laboratory underwater bistatic scattering measurements are reported for free, proud, and half-buried unexploded ordnances for 0 degrees and 90 degrees source angles. Forward echoes are larger than backscattered returns, and half burial significantly decreases the latter but not the former. Results agree with analytic predictions borrowed from radar. The forward echo and source signal are separated by measurements made with and without the target, a method not possible in a target search. For this, a method is described that uses knowledge of the source location and the hyperbolic character in time-cross range of the signals received at points along a line.

Bistatic scattering from submerged unexploded ordnance lying on a sediment.

The broadband bistatic target strengths (TSs) of two submerged unexploded ordnance (UXO) targets have been measured in the NRL sediment pool facility. The targets-a 5 in. rocket and a 155 mm projectile-were among the targets whose monostatic TSs were measured and reported previously by the authors. Bistatic TS measurements were made for 0 degrees (target front) and 90 degrees (target side) incident source directions, and include both backscattered and forward scattered echo angles over a complete 360 degrees with the targets placed proud of the sediment surface. For the two source angles used, each target exhibits two strong highlights: a backscattered specular-like echo and a forward scattered response. The TS levels of the former are shown to agree reasonably well with predictions, based on scattering from rigid disks and cylinders, while the levels of the latter with predictions from radar cross section models, based on simple geometric optics appropriately modified. The bistatic TS levels observed for the proud case provide comparable or higher levels of broadband TS relative to free-field monostatic measurements. It is concluded that access to bistatic echo information in operations aimed at detecting submerged UXO targets could provide an important capability.

Broadband acoustic scattering measurements of underwater unexploded ordnance (UXO).

In order to evaluate the potential for detection and identification of underwater unexploded ordnance (UXO) by exploiting their structural acoustic response, we carried out broadband monostatic scattering measurements over a full 360 degrees on UXO's (two mortar rounds, an artillery shell, and a rocket warhead) and false targets (a cinder block and a large rock). The measurement band, 1-140 kHz, includes a low frequency structural acoustics region in which the wavelengths are comparable to or larger than the target characteristic dimensions. In general, there are aspects that provide relatively high target strength levels ( approximately -10 to -15 dB), and from our experience the targets should be detectable in this structural acoustics band in most acoustic environments. The rigid body scattering was also calculated for one UXO in order to highlight the measured scattering features involving elastic responses. The broadband scattering data should be able to support feature-based separation of UXO versus false targets and identification of various classes of UXO as well.

Amyloplast sedimentation dynamics in maize columella cells support a new model for the gravity-sensing apparatus of roots.

Quantitative analysis of statolith sedimentation behavior was accomplished using videomicroscopy of living columella cells of corn (Zea mays) roots, which displayed no systematic cytoplasmic streaming. Following 90 degrees rotation of the root, the statoliths moved downward along the distal wall and then spread out along the bottom with an average velocity of 1.7 microm min(-1). When statolith trajectories traversed the complete width or length of the cell, they initially moved horizontally toward channel-initiation sites and then moved vertically through the channels to the lower side of the reoriented cell where they again dispersed. These statoliths exhibited a significantly lower average velocity than those sedimenting on distal-to-side trajectories. In addition, although statoliths undergoing distal-to-side sedimentation began at their highest velocity and slowed monotonically as they approached the lower cell membrane, statoliths crossing the cell's central region remained slow initially and accelerated to maximum speed once they reached a channel. The statoliths accelerated sooner, and the channeling effect was less pronounced in roots treated with cytochalasin D. Parallel ultrastructural studies of high-pressure frozen-freeze-substituted columella cells suggest that the low-resistance statolith pathway in the cell periphery corresponds to the sharp interface between the endoplasmic reticulum (ER)-rich cortical and the ER-devoid central region of these cells. The central region is also shown to contain an actin-based cytoskeletal network in which the individual, straight, actin-like filaments are randomly distributed. To explain these findings as well as the results of physical simulation experiments, we have formulated a new, tensegrity-based model of gravity sensing in columella cells. This model envisages the cytoplasm as pervaded by an actin-based cytoskeletal network that is denser in the ER-devoid central region than in the ER-rich cell cortex and is linked to stretch receptors in the plasma membrane. Sedimenting statoliths are postulated to produce a directional signal by locally disrupting the network and thereby altering the balance of forces acting on the receptors in different plasma membrane regions.

Fumaric acid: an overlooked form of fixed carbon in Arabidopsis and other plant species.

Photoassimilates are used by plants for production of energy, as carbon skeletons and in transport of fixed carbon between different plant organs. Many studies have been devoted to characterizing the factors that regulate photoassimilate concentrations in different plant species. Most studies examining photoassimilate concentrations in C3 plants have focused on analyzing starch and soluble sugars. However, work presented here demonstrates that a number of C3 plants, including the popular model organism Arabidopsis thaliana (L.) Heynh., and agriculturally important plants, such as soybean, Glycine max (L.) Merr., contain significant quantities of fumaric acid. In fact, fumaric acid can accumulate to levels of several milligrams per gram fresh weight in Arabidopsis leaves, often exceeding those of starch and soluble sugars. Fumaric acid is a component of the tricarboxylic acid cycle and, like starch and soluble sugars, can be metabolized to yield energy and carbon skeletons for production of other compounds. Fumaric acid concentrations increase with plant age and light intensity in Arabidopsis leaves. Moreover, Arabidopsis phloem exudates contain significant quantities of fumaric acid, raising the possibility that fumaric acid may function in carbon transport.

Columella cells revisited: novel structures, novel properties, and a novel gravisensing model.

A hundred years of research has not produced a clear understanding of the mechanism that transduces the energy associated with the sedimentation of starch-filled amyloplast statoliths in root cap columella cells into a growth response. Most models postulate that the statoliths interact with microfilaments (MF) to transmit signals to the plasma membrane (or ER), or that sedimentation onto these organelles produces the signals. However, no direct evidence for statolith-MF links has been reported, and no asymmetric structures of columella cells have been identified that might explain how a root turned by 90 degrees knows which side is up. To address these and other questions, we have (1) quantitatively examined the effects of microgravity on the size, number, and spatial distribution of statoliths; (2) re-evaluated the ultrastructure of columella cells in high-pressure frozen/freeze-substituted roots; and (3) followed the sedimentation dynamics of statolith movements in reoriented root tips. The findings have led to the formulation of a new model for the gravity-sensing apparatus of roots, which envisages the cytoplasm pervaded by an actin-based cytoskeletal network. This network is denser in the ER-devoid central region of the cell than in the ER-rich cell cortex and is coupled to receptors in the plasma membrane. Statolith sedimentation is postulated to disrupt the network and its links to receptors in some regions of the cell cortex, while allowing them to reform in other regions and thereby produce a directional signal.

Sequential isologous organ transplantation in inbred rats: pancreaticoduodenal transplants.

A total of 847 inbred Lewis rats of mixed sex were used in this pancreaticoduodenal (Pd) donor aging study. Pd grafts were taken from 9- to 12-month-old donors and transplanted into 3-month-old recipients (thus, the first generation Pd graft, or 1 Pd). After 9 to 12 months, the same Pd grafts were again harvested and transplanted into 3-month-old rats (thus the 2 Pd generation). This cycle was repeated to obtain the 3, 4, and 5 Pd series. Sequential transplantation was able to extend the Pd grafts' mean survival time to 32 months for fourteen 4 Pd grafts, and to 39.2 months for four 5 Pd grafts (the longest lived graft survived for 42 months). The pancreas and duodenal sections of the grafts remained normal throughout the entire study. However, the aortic sections of the grafts (which were harvested to include the superior mesenteric and celiac arteries) all exhibited moderate to massive atherosclerotic changes by the 5 Pd mean survival age of 39.2 months. Such histological changes commenced even before 21 months of Pd graft age in some animals, gradually progressing to dilation of the aorta (and subsequent narrowing of aortic tributaries), as well as formation of an eggshell-like inner membrane shielding the aortic intima, by 42 months. Such atherosclerotic changes precluded transplantations beyond the 5 Pd series.

The characterisation and cyclic production of a highly unsaturated homoserine lipid in Chlorella minutissima.

The marine alga Chlorella minutissima contains DGTS (diacylglyceryl-N,N,N-trimethylhomoserine) as a major component (up to 44% of total lipids). This lipid is absent from other members of the Chlorococcales, except for C. fusca, which contains DGTS as 1.3% of total lipids. Contrary to expectation, the DGTS is accompanied by PC (phosphatidylcholine) as the major phospholipid. DGTS is normally highly saturated in the C-1 position of glycerol, but in C. minutissima, both C-1 and C-2 are acylated with EPA (eicosapentaenoic acid, 20:5) in the major molecular species (over 90% of total). The DGTS level shows a marked rhythmic fluctuation with time which is inversely correlated with the level of MGDG (monogalactosyldiacylglycerol), the other major lipid. Improved NMR data and the first electrospray MS data on this lipid are presented.

Murine experimental autoimmune hepatitis: nonspecific inflammation due to adjuvant oil.

Experimental autoimmune hepatitis (EAH) has been induced in several strains of mouse by immunization with liver cytosol plus Freund's complete adjuvant. Our goal was to validate EAH in female C57Bl/6 mice and to compare the ability of immunization with liver cytosol and hepatocyte plasma membranes in Freund's complete (CFA) or incomplete (IFA) adjuvants to induce EAH. Control mice received Hank's balanced salt solution (HBSS), alone or an emulsion of HBSS in either CFA or IFA. The severity of hepatitis in coded liver sections was compared. EAH-like lesions were found not only in mice immunized with liver antigens in CFA or IFA but also in mice injected with either CFA or IFA. Mice injected with HBSS alone showed no hepatitis. These results indicate that immunization with neither liver nor mycobacteria cell wall antigens is required for induction of EAH-like lesions and suggest that the EAH in C57Bl/6 mice may be a nonspecific inflammatory response to adjuvant oil.

Suppressor function of liver mononuclear cells isolated during murine chronic graft-vs-host disease. II. Role of prostaglandins and interferon-gamma.

Mononuclear inflammatory cells (MC) isolated from the livers and spleens of mice with chronic graft-vs-host disease (CGVHD) to minor histocompatibility antigens (B10.D2----BALB/c) show defective proliferation when stimulated with Con A and LPS. In turn, both CGVHD liver and spleen cells suppress the proliferation of mitogen-stimulated normal spleen cells in a genetically unrestricted manner. The suppressor activity of CGVHD spleen cells is mediated by plastic nonadherent null (natural suppressor) cells and involves a soluble suppressor factor(s). In contrast, the suppressor activity of CGVHD liver cells is mediated by macrophages (M phi). In the current studies we show that the suppressor activity of CGVHD liver cells is also mediated by soluble factors and compare the roles of prostaglandins and interferon (IFN)-gamma in mediating defective proliferation and suppressor activities of CGVHD liver and spleen MC. Monoclonal antibody to IFN-gamma partially reversed the defective mitogen-stimulated proliferation of CGVHD spleen MC but had no effect on proliferative response of CGVHD liver MC. Indomethacin did not alter the low proliferative response of either CGVHD liver or spleen MC. Anti-IFN-gamma inhibited the ability of CGVHD spleen cells to suppress proliferation of Con A and LPS-stimulated B10.D2 spleen cells. In contrast, anti-IFN-gamma resulted in a small decrease in the ability of liver MC to suppress Con A (but not LPS)-stimulated cell proliferation. Indomethacin decreased the ability of both CGVHD liver and spleen cells to suppress Con A-stimulated proliferation but had inconsistent effects on LPS-stimulated proliferation. These results show that IFN-gamma and prostaglandins partially mediate the suppressor activity of CGVHD spleen MC. The suppressor activity of CGVHD liver MC also involves prostaglandins but is relatively independent of IFN-gamma.

Suppressor function of hepatic mononuclear inflammatory cells during murine chronic graft-vs-host disease. I. Macrophage-enriched cells mediate suppression in the liver.

Murine chronic graft-vs-host disease (CGBHD) to minor histocompatibility antigens (B10.D2----BALB/c) is characterized by inflammatory destruction of intrahepatic bile ducts, scleroderma-like skin lesions, and lymphoid involution. Spleen cells isolated from this model proliferate poorly when stimulated with mitogens. Previous reports indicate defective lymphocyte proliferation in this model is the result of active suppression induced by the graft-vs-host reaction in the spleen and is mediated by Thy 1.2-, sIg-, plastic nonadherent, splenic natural suppressor (NS) cells. To determine whether the intense CGVHD in the liver is associated with induction of suppression, we compared the suppressor activity of hepatic and splenic mononuclear inflammatory cells isolated concurrently during murine CGVHD. Both hepatic and splenic MC suppressed the proliferation of mitogen-stimulated normal spleen cells in a non-MHC, non-Mls restricted manner. T cells contributed to the suppressor activity of both populations. However, the suppressor activity of hepatic MC was mediated largely by a macrophage-enriched population of MC while that of splenic MC was mediated largely by NS cells.

Hepatic homing of mononuclear inflammatory cells isolated during murine chronic graft-vs-host disease.

Liver injury in murine chronic graft-vs-host disease (CGVHD) to minor histocompatibility Ag, B10.D2----BALB/c (600 rad), is characterized by mononuclear cell inflammation and necrosis of interlobular bile ducts. Bile duct destruction in this model is similar to that which occurs in human CGVHD, late liver transplant rejection, and primary biliary cirrhosis. This model provides a unique opportunity to isolate mononuclear inflammatory cells from the liver during CGVHD, study their functions, and investigate the immunologic mechanisms responsible for bile duct destruction. In the present study, we compared the in vivo organ homing of mononuclear inflammatory cells (MC) isolated from the liver and spleen during the course of CGVHD. MC isolated from the liver showed a progressive increase in homing to the livers of BALB/c mice from day 7 through 42. In contrast, the hepatic homing of MC isolated from the spleen peaked at day 21 and subsequently declined. CGVHD spleen MC showed a progressive increase in homing to the spleen of BALB/c mice whereas CGVHD liver MC showed no change over time. Homing to other organs was negligible. The hepatic and splenic homing of MC isolated during CGVHD was significantly greater in BALB/c (host) mice than in B10.D2 (donor) mice. Autoradiography was used to determine the intrahepatic sites at which CGVHD liver MC accumulate after i.v. injection into BALB/c mice. The results indicated that MC isolated from the liver when bile duct inflammation is most intense accumulate preferentially in hepatic portal spaces in close proximity to interlobular bile ducts. These results suggest that hepatic homing by CGVHD liver MC is specific for minor histocompatibility Ag expressed on host biliary epithelial cells. These data support the hypothesis that bile duct destruction in murine CGVHD is mediated by MC that are sensitized to minor histocompatibility Ag expressed by host biliary epithelial cells.